Usmle Step1 Mcq Study Online Questions Review

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USMLE STEP1 MCQ STUDY ONLINE QUESTIONS REVIEW

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USMLE STEP1 MCQ STUDY ONLINE QUESTIONS REVIEW

1> A no rmal, healthy, 25-year-old man lives at the beach. His twin brother has

been living in a mountain cabin for the past 2 years. Which of the

following indices would be expected to be higher in the man living at

sea level?

A. Diameter of pulmonary vesselsB. Erythropoietin production

C. Mitochondrial density in a muscle biopsy

D. Renal bicarbonate (HCO3-) excretion

E. Respiratory rate

Answer

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2>A woman presents to a dermatologist because she has lost almost all the

hair on her body, including scalp hair, eye brows, eye lashes, arm pit and

groin hair, and the fine hairs on her body and extremities. She most likely

has a variant of which of the following?

A. Alopecia areata

B. Androgenic alopecia

C. Chronic cutaneous lupus erythematosus

D. Lichen planopilaris

E. Trichotillomania

Answer

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3>The greater omentum is derived from which of the following embryonic

structures?

A. Dorsal mesoduodenum

B. Dorsal mesogastrium

C. Pericardioperitoneal canal

D. Pleuropericardial membranes

E. Ventral mesentery

Answer

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4>A 34-year-old woman is prescribed an antidepressant, which she has taken

for the past 3 months. She is on no other medications and is in generally

good health. After attending a party, at which she consumed wine and

cheese, she is rushed to the emergency room with tachycardia, headache,

and a blood pressure of 200/100. Which antidepressant is she most likely

taking?A. Amitriptyline

B. Fluoxetine

C. Phenelzine

D. Sertraline

E. Trazodone

Answer

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5>Which of the following hormones is secreted by anterior pituitary cells

that stain with acidic dyes?

A. ACTH

B. FSH

C. LH

D. Prolactin

E. TSH

LE STEP1 MCQ STUDY ONLINE QUESTIONS REVIEW http://medicaltalk.net/Thread-usmle-step1-mcq-study-online-question

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6>A 23-year-old male graduate student gets into a serious argument with

one of his college professors, making a physical threat to the professor,

and necessitating a call to campus security. The argument was precipitated

by an incident between the professor and the student's girlfriend; when

the professor corrected the student's girlfriend in class, the student

felt the professor was verbally abusive. Which of the following is

the most likely diagnosis ?

A. Dependent personality disorder

B. Histrionic personality disorder

C. Narcissistic personality disorder

D. Paranoid personality disorder

E. Passive aggressive personality disorderAnswer

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7>Which of the following would shift the oxygen-hemoglobin dissociation curve

to the right?

A. Carbon monoxide poisoning

B. Decreased PCO2

C. Decreased pH

D. Decreased temperature

E. Decreased 2,3-DPG

Answer

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8>The wife of a 48-year-old male patient brings him to the emergency room and

says that his memory has progressively gotten worse over the last several

years. She also says his personality has been changing. The physician notes

abnormal writhing movements of the man's limbs and hyperreactive reflexes. MRI reveals a loss of volume in the neostriatum and cortex. This disease

is inherited via an

A. autosomal dominant trait

B. autosomal recessive trait

C. x-linked dominant trait

D. x-linked recessive trait

Answer

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9>A man presents to a dermatologist because of a severe mucocutaneous rash

that involves most of his body, including his palms and soles. Questioning

reveals that he is a merchant marine who several months previously had an

encounter with a prostitute in Southeast Asia. Which of the following is

the most likely causative agent of this rash?

A. Herpes simplex I

B. Herpes simplex II

C. HIVD. Neisseria gonorrhoeae

E. Treponema pallidum

Answer

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10>A patient with familial hypercholesterolemia undergoes a detailed serum

lipid and lipoprotein analysis. Studies demonstrate elevated cholesterol

in the form of increased LDL without elevation of other lipids.

This patient's hyperlipidemia is best classified as which of the

following types?

A. Type 1

B. Type 2a

C. Type 2b

D. Type 3

E. Type 5

Answer

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11>A mutation affecting the development of the diencephalon could interfere

with the secretion of which of the fo llowing hormones?

A. Adrenocorticotrophic hormone (ACTH)

B. Epinephrine

C. Oxytocin

D. Prolactin

E. Thyroid stimulating hormone (TSH)

Answer

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12>Which of the following organisms is the most common cause of

community-acquired pneumonia?

A. Chlamydia pneumoniae


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B. Haemophilus influenzae

C. Mycoplasma pneumoniae

D. Staphylococcus aureus

E. Streptococcus pneumoniae

Answer

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13>A 54-year-old male with acute lymphocytic leukemia develops a blast crisis.

He is treated with intensive systemic chemotherapy. Following treatment,

the patient will be at increased risk for the development of

A. bile pigment gallstones

B. cholesterol gallstones

C. cystine kidney stonesD. struvite kidney stones

E. uric acid kidney stones

Answer

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14>A 65-year-old man with mild heart failure is treated with a loop diuretic

. A few days later the man complains of muscle weakness. Laboratory results

are shown below. Arterial PCO2: 48 mm Hg Arterial pH: 7.49

Plasma HCO3-: 35 mEq/L Which of the following is most likely

decreased in this man?

A. Plasma aldosterone

B. Plasma potassium

C. Potassium excretion

D. Renin secretion

E. Sodium excretion

Answer

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15>A 27-year-old white male presents with a 3-week history of several swollen

and painful toes and knees. He has a past history of conjunctivitis. He

also describes some low back stiffness that is more severe in the morning.

Which of the following is the most likely diagnosis?

A. Gout

B. Lyme disease

C. Reiter's syndrome

D. Rheumatoid arthritis

E. Septic arthritis

Answer

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16>A 37-year-old woman who was diagnosed with AIDS 3 years earlier is unable

to work, is physically debilitated, and requests her physician to provide

her with medications with which to take her own life. The most common

emotional disorder that results in such requests by patients isA. bipolar I disorder, manic type

B. borderline personality disorder

C. factitious disorder

D. major depressive disorder

E. schizophrenic disorder

Answer

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17>

A 25-year-old man presents with a chief complaint of persistent,

high-pitched ringing noises in his ears. Questioning reveals that

he has also been losing his balance lately. CT of the head demonstrates

bilateral tumors involving the vestibulocochlear nerve. Which of the

following chromosomes contains the tumor suppressor gene most likely to

be involved in this case?

A. 5q

B. 13q

C. 17qD. 18q

E. 22q

Answer

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18> An autopsy is performed on a man who suddenly began vomiting voluminous

quantities of blood and exsanguinated. Which of the following organisms is most

likely implicated in the pathogenesis of this disease?

A. Cryptosporidium parvum

B. Entamoeba histolytica

C. Escherichia coli

D. Helicobacter pylori

E. Mycobacterium tuberculosis

Answer


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19>During embryological development, hematopoiesis occurs in different organs

at different times. Which of the following are the correct organs, in the

correct sequence, at which hematopoiesis occurs embryologically?

A. Amnion, yolk sac, placenta, bone marrow

B. Placenta, liver and spleen, yolk sac, bone marrow

C. Placenta, spleen and lymphatic organs, bone marrow

D. Yolk sac, bone marrow, liver and spleen

E. Yolk sac, liver, spleen and lymphatic organs, bone marrow

Answer

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20>A 27-year-old male is brought into the emergency room by the police,

who found him walking aimlessly, shouting the names of former Presidents.

Urine toxicology is negative, and the man appears to be oriented with

respect to person, place, and time. He has had five similar admissions

over the past year. Attempts to interview the patient are fruitless,

as he seems easily derailed from his train of thought. A phone call

to a friend listed in the chart provides the additional in formation

that the man is homeless, and unable to care for himself. This patient

is exhibiting the signs and symptoms of

A. schizoaffective disorder

B. schizoid personality disorder

C. schizophrenia

D. schizophreniform disorder

E. schizotypal personality disorder

Answer

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21>Molecular genetic studies are performed on a family with known familial

hypercholesterolemia. In this particular family, the defect in the LDL

receptor gene involves a messenger mutation near the 11th exon, in the

region of homology with epidermal growth factor receptor precursor. A

defect at this site would be most likely to produce which of the following

effects?

A. Decreased transcription of LDL receptor gene

B. Poor internalization of LDL bound to LDL receptor

C. Poor retention of the LDL receptor in the membrane

D. Reduced binding of LDL

E. Trapping of the LDL receptor in the endoplasmic reticulum

Answer

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22>A 27-year-old woman is giving birth. During the birth, the placentalmembranes tear and amniotic fluid is expressed into a lacerated cervical

vein. Which of the following is the woman most likely to experience

immediately following this event?

A. Hemiplegia

B. Placental abruption

C. Renal failure

D. Respiratory distress

E. Splinter hemorrhages

Answer

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23>A 30-year-old pregnant woman complains to her physician of feeling very

tired during her pregnancy. A complete blood count with differential

reveals a hematocrit of 30%, with hypersegmented neutrophils and large,

hypochromic red cells. Deficiency of which of the following would be

most likely to produce these findings?

A. Ascorbic acidB. Calcium

C. Copper

D. Folate

E. Iron

Answer

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24>An otherwise healthy 3-year-old child is brought to the pediatrician with

umbilicated, flesh-colored papules on his trunk. This condition is related

to infection with which of the following viruses?

A. Cytomegalovirus

B. Herpesvirus 6

C. Parvovirus

D. Poxvirus


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E. Variola

Answer

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25>Which of the following renal structures is most medially located?

A. Major calyx

B. Minor calyx

C. Renal cortex

D. Renal pelvis

E. Renal pyramid

Answer

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26>A 48-year-old female is being treated for breast carcinoma. Over the past

few days, she has been complaining of dysuria and frequency. Laboratory

examination revealed the presence of microscopic hematuria. The next day

the patient developed gross hematuria. Which of the following agents most

likely caused the development of these signs and symptoms?

A. Cyclophosphamide

B. Mitomycin

C. Paclitaxel

D. Tamoxifen

E. Vincristine

Answer

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27>A child who has had abnormal development of the membranous bones has a

broad skull with associated facial and dental anomalies. Which other bones

are most likely to also be affected?

A. ClaviclesB. Femurs

C. Metatarsals

D. Phalanges

E. Tibias

Answer

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28>A 3-year-old child is referred to a major medical center because of an

abdominal mass arising from his right adrenal gland. Biopsy of the lesion

demonstrates sheets of small cells with hyperchromatic nuclei containing

occasional pseudorosettes composed of circles of tumor cells with central

young nerve fibers arising from the tumor cells. Which of the following

oncogenes is associated with this patient's tumor?

A. erb-B2

B. c-myc

C. L-myc

D. N-mycE. ret

Answer

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29>A 3-year-old child develops headaches and is brought to the family doctor.

Funduscopic examination reveals papilledema; one retina also shows a very

vascular tumor. CT of the head demonstrates a cystic tumor of the

cerebellum. This child has a high likelihood of later developing

which of the following?

A. Berry aneurysm of the basilar system

B. Bilateral renal cell carcinoma

C. Cancer of a peripheral nerve

D. Choreiform movements related to decreased GABA and acetylcholine

E. Serum cholesterol of greater than 700 mg/dL

Answer

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30>Administration of an experimental drug that acts on PNS myelin is shown

to increase the space constant of an axon in a peripheral nerve. Action

potentials traveling down the axon would be predicted to be

A. faster

B. larger

C. slower

D. smaller

E. unchanged

Answer

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31>A 26-year-old man presents to h is physician with a chronic cough. The man

is a smoker, and states that he also gets f requent headaches and aches in

his legs when he exercises. Chest x-ray demonstrates notching of his


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ribs. Which of the following undiagnosed congenital defects may be

responsible for these findings?

A. Coarctation of the aorta

B. Eisenmenger's syndrome

C. Tetralogy of Fallot

D. Transposition of great vessels

E. Ventricular septal defect

Answer

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32>A 36-year-old Asian male complains of difficulty swallowing.

Esophagoscopy reveals a polypoid mass that is subsequently biopsied.

In addition to tumor cells, the esophageal biopsy show normal smoothmuscle and striated muscle in the same section. Which portion of the

esophagus was the source of this biopsy?

A. Lower esophageal sphincter

B. Lower third of the esophagus

C. Middle third of the esophagus

D. Upper esophageal sphincter

E. Upper third of the esophagus

Answer

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33> A 25-year-old woman with sickle cell anemia complains of steady pain in

her right upper quadrant with radiation to the right shoulder, especially

after large or fatty meals. Her physician diagnoses gallstones. Of which

of the following compounds are these stones most likely composed?

A. Calcium bilirubinate

B. Calcium oxalateC. Cholesterol

D. Cholesterol and calcium bilirubinate

E. Cystine

Answer

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34>A 54-year-old alcoholic presents with complaints of tremors and muscle

twitching. Physical examination reveals the presence of Trousseau's s ign.

Laboratory data show that serum magnesium is < 1 mEq/L

(normal, 1.4 - 2.2 mEq/L). Which of the following findings

would be most consistent with this information?

A. Decreased serum calcium

B. Decreased serum phosphate

C. Increased bone density

D. Increased plasma parathyroid hormone concentration

E. Increased urinary cAMP concentrationAnswer

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35>A young boy presents with failure to thrive. Biochemical analysis of a

duodenal aspirate after a meal reveals a deficiency of enteropeptidase

(enterokinase). The levels of which of the following digestive enzymes

would be affected?

A. Amylase

B. Colipase

C. Lactase

D. Pepsin

E. Trypsin

Answer

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36>A Guatemalan child with a history of meconium ileus is brought to a

clinic because of a chronic cough. The mother notes a history of respiratorytract infections and bulky, foul-smelling stools. After assessment of the

respiratory tract illness, the physician should also look for signs of

A. cystinuria

B. hypoglycemia

C. iron deficiency anemia

D. sphingomyelin accumulation

E. vitamin A deficiency

Answer

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37>An infant is born with an abnormally developed falciform ligament.

The hepatogastric and hepatoduodenal ligaments are also malformed

. These developmental anomalies are most likely due to abnormal

development of the


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A. dorsal mesoduodenum

B. dorsal mesogastrium

C. pericardioperitoneal canal

D. pleuropericardial membranes

E. ventral mesentery

Answer

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38>A 26-year-old man is admitted through the emergency department to the

hospital for a heroin overdose. His heart rate is 45 beats/min, and his

blood pressure is 75/40 mm Hg. Which of the following best depicts the

results from an arterial blood sample ?

pH PaCO2 (mm Hg) HCO3- (mEq/L)A. 7.22 66 26

B. 7.34 29 15

C. 7.40 40 24

D. 7.47 20 14

E. 7.49 48 35

Answer

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39>A 15-year-old boy presents to his physician with several weeks of slowly

worsening pruritus of both of his feet. He is otherwise well and taking

no medications. On examination, he has bilateral, erythematous, dry

scaling lesions that are most obvious in the interdigital web spaces

and on the soles. There is no bleeding or exudate. What would most

likely be found in a potassium hydroxide (KOH) mount of a scrapin

g of the affected skin?

A. Branching hyphae with rosettes of conidia

B. Branching, septate hyphaeC. Budding yeasts

D. Hyphae, arthroconidia, and blastoconidia

E. Pigmented, septate hyphal f ragments

F. Short, curved hyphae and round yeasts

Answer

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40>A 48-year-old white female secretary presents with progressive difficulty

typing over the past month. She also notes that her hands begin to feel

numb and weak after typing for long periods of time. Upon testing,

which of the following deficits would be predicted?

A. Difficulty in abducting the fifth finger

B. Difficulty in adducting the thumb

C. Difficulty in flexing digits two and three at the metacarpophalangeal joints

D. Loss of sensation over the lateral half of the dorsum of the hand

E. Loss of sensation over the lateral half of the palm

F. Loss of sensation over the medial half of the dorsum of the handG. Loss of sensation over the medial half of the palm

Answer

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41>A 15-year-old girl is brought into the emergency room with severe abdominal

pain and a fever. Laboratory examination is remarkable for an elevated

white blood cell count and a pregnancy test is positive. Upon questioning,

it is determined that she attempted to terminate her pregnancy by

inserting a sharp object into her vagina. The physician determines

that the wall of the posterior fornix of the vagina has been penetrated. Into what region did the sharp object penetrate?

A. Deep perineal pouch

B. Ischioanal space

C. Rectouterine space

D. Rectovesical space

E. Vesicouterine space

Answer

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42>Which of the following is found in the respiratory zone of the lung?

A. Goblet cells

B. Main bronchi

C. Mucous cells

D. Terminal bronchioles

E. Type I epithelial cells

Answer

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43>A patient presents with a bulge in the groin, which his physician

diagnoses as an inguinal hernia. To determine whether it is an indirect

or direct inguinal hernia, the physician applies pressure over the deep

inguinal ring while palpating over the superficial inguinal ring. The


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patient is then asked to cough. The physician notes that the hernia

does not push out of the abdomen and concludes that it is an indirect

inguinal hernia. Where did the physician apply pressure?

A. Immediately lateral to the lacunar ligament

B. Immediately lateral to the pubic tubercle

C. Immediately medial to the femoral vein

D. One half inch above the midpoint of the inguinal ligament

E. One half inch below the midpoint of the inguinal ligament

Answer

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44>A 68-year-old woman presents for a routine check-up. Her only complaint

is that she occasionally experiences a little swelling in her ankles.Her serum potassium is 3.5 mEq/L, so the physician wants to avoid

unnecessary potassium losses. Which of the following diuretics would

be most appropriate for this patient?

A. Furosemide

B. Hydrochlorothiazide

C. Indapamide

D. Metolazone

E. Spironolactone

Answer

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45>A 15-year-old boy is evaluated by a clinician for failure to develop normal

male secondary sexual characteristics. Physical examination reveals small

testes, a small penis, and gynecomastia. The boy has had some dif ficulties

in school, and the parents say that the school psychometrist said he had

an IQ of 90. This patient's condition is most likely to be related to

which of the following?A. Deletion

B. Nondisjunction of an autosomal chromosome

C. Nondisjunction of a sex chromosome

D. Non-Robertsonian translocation

E. Robertsonian translocation

Answer

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46>A 5-year-old boy falls off his bike and fractures his humerus. He is taken

to the emergency room, and the bone is set by one of the emergency room

physicians. Which of the following is responsible for producing the

majority of the new bone that will reunite the two fragments?

A. Cancellous bone

B. Cartilage

C. Compact bone

D. Marrow

E. PeriosteumAnswer

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47>A 25-year-old man presents with a 4-cm mass above the clavicle. Chest X-ray

demonstrates marked mediastinal widening. Excisional biopsy of the

supraclavicular mass demonstrates areas with the appearance shown in

the photomicrograph above. The large cell (indicated with the arrow)

is most likely which of the fo llowing?

A. Langhans cell

B. LE cell

C. Mott cell

D. Reed-Sternberg cell

E. Touton cell

Answer

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48>A 50 -year-old electrician reports pain in h is left upper extremity and

tingling and numbness in his 4th and 5th digits of his left hand. Ther

e is mild swelling of the left hand. The man reports most of his pain

and numbness occurs when he is doing electrical work with his arms

overhead. X-ray reveals the presence of a cervical rib. Which of the

following structures is most likely being compressed?

A. Axillary artery

B. Brachial artery

C. Brachiocephalic artery

D. Subclavian artery

E. Subscapular artery

Answer

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49>The left adrenal vein drains directly into which of the following veins?

A. Hemiazygos vein

B. Inferior vena cava

C. Left renal vein

D. Splenic vein

E. Superior mesenteric vein

Answer

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50>To which of the following diseases is pyruvate kinase deficiency most

similar clinically?A. a-thalassemia

B. b-thalassemia

C. Glucose-6-phosphate dehydrogenase deficiency

D. Hereditary spherocytosis

E. Iron deficiency anemia

Answer

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Answers

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1>The correct answer is A. A number of physiologic changes occur in a person living at high altitude. The diminished barometric pressure at high

altitude causes alveolar hypoxia and arterial hypoxia. Pulmonary vasoconstriction occurs in response to alveolar hypoxia; therefore, the diameter of the

pulmonary vessels would be greater in the brother living at sea level. All the other choices describe physiologic processes that would be enhanced by

living at high altitude.

Increased erythropoietin production (choice B), caused by arterial hypoxia, leads to increases in hematocrit in people living at high altitude.Mitochondrial density increases (choice C) in people chronically exposed to the hypoxemia caused by living at high altitude.

At high altitudes, the ventilation rate increases, causing a respiratory alkalosis. The kidney then compensates by increasing the excretion of HCO3-

(choice D).

Increasing the rate of respiration (choice E) is a very useful adaptation to the hypox ic conditions of high altitude. The primary stimulus is the hypox ic

stimulation of peripheral chemoreceptors.

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2>The correct answer is A. Alopecia areata is caused by an autoimmune attack on hair follicles. It has a wide range of clinical severity, with most cases

involving a localized patch of hair (which regrows within 1 year in half of the patients). The hair that does regrow may be gray or depigmented. More

severe cases can involve the entire scalp (alopecia totalis) or, as in this patient, the entire body surface (alopecia universalis). These more severe cases

are less likely to resolve adequately. Treatment of alopecia areata is often unsuccessful, but topical steroids are typically tried.

Androgenic alopecia (choice B) is common male pattern baldness.

Chronic cutaneous lupus erythematosus (choice C) can produce localized baldness.

Lichen planopilaris (choice D) can produce localized baldness.

Trichotillomania (choice E), also called traumatic alopecia, is alopecia due to trauma, such as hair pulling or tight braids.

--------------- --------------- -------------- ---------------- --------------- -----3>The correct answer is B. Both the omental bursa and the greater omentum are

derived from the dorsal mesogastrium, which is the mesentery of the stomach region.

The dorsal mesoduodenum (choice A) is the mesentery of the developing duodenum, which later disappears so that the duodenum and pancreas cometo lie retroperitoneally.

The pericardioperitoneal canal (choice C) embryologically connects the thoracic and peritoneal canals.

The pleuropericardial membranes (choice D) become the pericardium and contribute to the diaphragm.

The ventral mesentery (choice E) forms the falciform ligament, ligamentum teres, and lesser omentum.

--------------- -------------- --------------- ---------------- ------------- -------4>The correct answer is C. Wine and cheese (and many other fermented foods)

contain tyramine, an indirect sympathomimetic that can trigger excess catecholamine release and lead to a hypertensive crisis when ingested by patients

taking MAO inhibitors. The only such drug listed among the answer choices is phenelzine. Other MAO inhibitors with similar effects include

tranylcypromine, isocarboxazid, and iproniazid. Whenever this particular drug class is mentioned in a question stem, consider the possibility of

interactions with foods or o ther medications the patient may have taken.

Amitriptyline (choice A) is a tricyclic antidepressant. Tricyclic antidepressant drugs (particularly amitriptyline) are known for their anticholinergic side

effects. They also produce postural hypotension (because they block alpha-adrenergic receptors) and are sedative.

Fluoxetine and sertraline (choices B and D) are antidepressants that are selective serotonin reuptake inhibitors (SSRIs). Fluoxetine is also useful in

treatment of obsessive-compulsive disorders.

Trazodone (choice E) is an atypical antidepressant with substantial sedative side effects. Its most serious side effect is priapism, a medical emergency.

--------------- -------------- --------------- -------------- --------------- -------5>The correct answer is D. The cells of the anterior pituitary can be classified as

chromophils (love dyes) or chromophobes (do no t stain with dyes). The chromophils can be further divided into acidophils (stain with acidic dyes) and

basophils (stain with basic dyes). The acidophils include the somatotropes, which secrete growth hormone, and the mammotropes, which secreteprolactin. The basophils include the corticotropes, which secrete ACTH (choice A) , the gonadotropes, which secrete FSH and LH (choices B and C), and

the thyrotropes, which secrete TSH (choice E).

--------------- -------------- --------------- ---------------- ------------- -------6>The correct answer is D. Persons with this condition often perceive attacks and

danger in relatively innocuous situations. They are quick to respond with anger, and, because personality disorders are ego-syntonic, individuals with

personality disorders do not believe themselves to be in error.

The individual with dependent personality disorder (choice A) does not confront others but wants o thers to take care of him.

The individual with histrionic personality disorder (choice B) is flamboyant and seductive, not confrontational and angry.

The individual with narcissistic personality disorder (choice C) is characterized by feelings of entitlement because they are so "special."

And the individual with passive aggressive personality disorder (choice E) expresses anger indirectly (e.g., always being late) rather than confronting

--------------- -------------- --------------- -------------- --------------- -------7>The correct answer is C. The loading of O2 is facilitated when the oxygen

dissociation curve shifts to the left, and the unloading of O2 is facilitated when the oxygen dissociation curve shifts to the right. A good way to

remember the conditions that promote dissociation of O2 is to think of exercising muscle, which has decreased pH (choice C) because of the

accumulation of lactic acid, increased PCO2 (compare with choice B) because of the increased rate of aerobic metabolism, increased temperature

(compare with choice D), and increased 2,3-DPG (2,3-diphosphoglycerate; compare with choice E) because of increased glycolysis.


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Carbon monoxide poisoning (choice A) left-shifts the oxygen dissociation curve, which interferes with the unloading of O2. Carbon monoxide also

strongly binds to available sites on hemoglobin.

--------------- -------------- --------------- -------------- --------------- -------8>The correct answer is A. This patient has Huntington's disease, which has

autosomal dominant inheritance. It is characterized by severe degeneration of the caudate nucleus along with degenerative changes in the putamen and

cortex. In addition to chorea, these patients frequently suffer from athetoid (writhing) movements, progressive dementia, and behavioral disorders.

--------------- -------------- --------------- -------------- --------------- -------9>The correct answer is E. The rash described is that of secondary syphilis,

caused by Treponema pallidum. Involvement of palms and soles by a rash is unusual, and secondary syphilis should come to mind. Not all patients with

secondary syphilis have a severe form of the rash, and consequentially some cases are missed. Primary syphilis takes the form of a painless, button-like

mass called chancres. Tertiary syphilis, which is now rare, has a propensity for involving the aorta and central nervous system and can also cause

"gummas" (granulomatous-like lesions) in many sites, notably including liver and bone.

Herpes simplex I (choice A) usually causes perioral vesicular lesions.

Herpes simplex II (choice B) usually causes genital vesicular lesions.

HIV (choice C) does not itself cause a rash, although co-infection with other organisms can result in a rash.Neisseria gonorrhoeae (choice D) does not typically cause a rash.

--------------- --------------- -------------- ---------------- --------------- -----10>The correct answer is B. Hyperlipidemia has been subclassified based on the

lipid and lipoprotein profiles. Type 2a, which this patient has, can be seen in a hereditary form, known as familial hypercholesterolemia, and also in

secondary, acquired forms related to nephritic syndrome and hyperthyroidism. The root problem appears to be a deficiency of LDL receptors, which

leads to a specific elevation of cholesterol in the form of increased LDL. Heterozygotes for the hereditary form generally develop cardiovascular disease

from 30 to 50 years of age. Homozygotes may have cardiovascular disease in childhood.

Type 1 (choice A) is characterized by isolated elevation of chylomicrons.

Type 2b (choice C) is characterized by elevations of both cholesterol and triglycerides in the fo rm of LDL and VLDL.

Type 3 (choice D) is characterized by elevations of triglycerides and cholesterol in the form of chylomicron remnants and IDL.

Type 5 (choice E) is characterized by elevations of triglycerides and cholesterol in the form of VLDL and chylomicrons.

--------------- -------------- --------------- -------------- --------------- -------11The correct answer is C. The neurohypophysis (posterior pituitary) is derived

from an evagination of diencephalic neurectoderm. This structure is responsible for releasing oxytocin and vasopressin to the general circulation. Both

hormones are synthesized in cell bodies contained within the hypothalamus.

ACTH (choice A), prolactin (choice D), and TSH (choice E) are all synthesized and released by the anterior pituitary, or adenohypophysis, which is

derived from an evagination of the ectoderm of Rathke's pouch, a diverticulum of the primitive mouth. Remnants of this pouch may give rise to a

craniopharyngioma in later life.

Epinephrine (choice B) is synthesized and released into the circulation by the adrenal medulla, a neural crest derivative.--------------- --------------- -------------- ---------------- --------------- -----12>The correct answer is E. The most common bacteria implicated in community-

acquired pneumonia is the pneumococcus, Streptococcus pneumoniae. Other organisms frequently implicated in patients less than age 60 without

comorbidity include Mycoplasma pneumoniae, respiratory viruses, Chlamydia pneumoniae, and Haemophilus influenzae. When community-acquired

pneumonia occurs in elderly patients or patients with comorbidity, aerobic gram-negative bacilli and Staphylococcus aureus are added to the list.

The organisms listed in choices A, B, and C are important causes of community-acquired pneumonia, but are not the most frequent causes.

Staphylococcus aureus (choice D) is an important cause of community-acquired pneumonia (particularly in the elderly and in patients with comorbidity),

but is not the most frequent cause.

--------------- --------------- -------------- ---------------- --------------- -----13>The correct answer is E. Uric acid kidney stones in patients with leukemia are

secondary to increased production of uric acid from purine breakdown during periods of active cell proliferation, especially following treatment. Vigorous

hydration and diuresis are generally instituted after the diagnosis of acute leukemia is made. Uric acid kidney stones are also associated with inborn

errors of purine metabolism, such as gout.

Pigment gallstones (choice A) are associated with hemolytic disease. The incidence of this type of gallstone is not increased in treated leukemias.

Cholesterol gallstones (choice B) are associated with diabetes mellitus, obesity, pregnancy, birth control pills, and celiac disease.

Cystine kidney stones (choice C) are rare; they are found in cystinuria.

Struvite kidney stones (choice D) are associated with infection by urea-splitting organisms, such as Proteus.

--------------- --------------- -------------- ---------------- --------------- -----14>The correct answer is B. The data shown in the table indicate that the man

has developed metabolic alkalosis (increased PCO2, pH, and HCO3-), which occurs commonly with overuse of diuretics (thiazides and loop diuretics).The overuse of a loop d iuretic increases the excretion of sodium (choice E) and potassium (choice C) by the kidneys. The increase in potassium

excretion leads to a decrease in plasma potassium levels (choice B) . The decrease in plasma potassium stimulates aldosterone secretion, which raises

plasma aldosterone levels (choice A). The sodium depletion stimulates renin secretion (choice D), which in turn raises angiotensin II levels in the plasma

(which also stimulates aldosterone secretion

--------------- --------------- -------------- ---------------- --------------- -----15>The correct answer is C. This is a case of Reiter's syndrome. Patients typically

present with the acute onset of arthritis (usually asymmetric and additive), with involvement of new joints occurring over a period of a few days to 2

weeks. Joints of the lower extremities are the most commonly involved, but wrists and fingers can also be affected. Dactylitis (sausage digit), a dif fuse

swelling of a so litary finger or toe, is a distinctive feature of Reiter's arthritis and psoriatic arthritis. Tendonitis and fasciitis are common. Spinal pain and

low back pain are common. Conjunctivitis, urethritis, diarrhea, and skin lesions are also associated with Reiter's syndrome. Up to 75% of patients are

HLA-B27 positive. Microorganisms which can trigger Reiter's syndrome include Shigella spp., Salmonella spp., Yersinia spp., Campylobacter jejuni, and

Chlamydia trachomatis. Most patients are younger males.

Gout (choice A) usually presents as an explosive attack of acute, very painful, monarticular inflammatory arthritis. Hyperuricemia is the cardinal feature

and prerequisite for gout. The first metatarsophalangeal joint is involved in over 50% of first attacks.

Lyme disease (choice B), caused by Borrelia burgdorferi, presents with a red macule or papule at the site of the tick bite. This lesion, called erythema

chronicum migrans, slowly expands to fo rm a large annular lesion with a red border and central clearing. The lesion is warm, but usually not painful. The

patient also has severe headache, stiff neck, chills, arthralgias, and profound malaise and fatigue. Untreated infection is associated with development of

arthritis. The large joints (e.g., knees) are usually involved with the arthritis lasting for weeks to months.Rheumatoid arthritis (choice D) begins insidiously with fatigue, anorexia, generalized weakness, and vague musculoskeletal symptoms leading up to the

appearance of synovitis. Pain in the affected joints, aggravated by movement, is the most common manifestation of established rheumatoid arthritis.

Generalized stiffness is frequent and is usually greatest after periods of inactivity. Morning stiffness of greater than 1 hour in duration is very

characteristic. Rheumatoid arthritis is more common in females. The metacarpophalangeal and proximal interphalangeal joints of the hands are

characteristically involved.

Septic arthritis (choice E) is caused by a variety of microorganisms, including Neisseria gonorrhoeae and Staphylococcus aureus. Hematogenous spread is

the most common route in all age groups. 90% of patients present with involvement of a single joint, usually the knee. The usual presentation is

moderate-to-severe pain, effusion, muscle spasm, and decreased range of motion. Peripheral leukocytosis and a left shift are common. Disseminated

gonococcal infections present as fever, chills, rash, and articular symptoms. Papules progressing to hemorrhagic pustules develop on the trunk and

extensor surfaces of the distal extremities. Migratory arthritis and tenosynovitis of multiple joints is common.

--------------- --------------- -------------- ---------------- --------------- -----16>The correct answer is D. Many people who request physician-assisted suicide

have one of two conditions present: either a poorly controlled painful condition or severe depression. If the painful condition is adequately treated or the

depression is brought under good medical control, the request for physician assistance in terminating the situation is typically withdrawn. It is important

to note that bringing these conditions under control requires the intervention of caregivers who are specifically trained in the management of these two


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conditions; primary care physicians usually are not adequately trained to address these difficult presentations.

While patients who are diagnosed as bipolar disorder (choice A), borderline personality disorder (choice B), and schizophrenic disorder (choice E) often

make suicide attempts (and frequently complete those attempts), they do no t generally ask their physician for assistance in the suicide.

Persons with factitious disorder (choice C) are seeking primary gain, often for dependency needs, and are seeking to enter the "sick role" not the "dead

role."

--------------- --------------- -------------- ---------------- --------------- -----17>The correct answer is E. The patient has bilateral acoustic neuromas, probably

due to neurofibromatosis type II (over 90% of patients with NF-2 develop bilateral acoustic neuromas). This condition is a associated with the NF-2,

gene, located on 22q (note all the 2's) . Patients often develop meningiomas, gliomas, and schwannomas of cranial and spinal nerves.

5q (choice A) contains the APC tumor suppressor gene, which is associated with familial and sporadic colorectal cancers.

13q (choice B) contains the Rb tumor suppressor gene, which is associated with retinoblastoma and osteosarcoma.

17q (choice C) contains both the NF-1 tumor suppressor gene, which is associated with neurofibromatosis type I, and the p53 tumor suppressor gene,

associated with many human cancers.

18q (choice D) contains both the DCC gene, which is associated with colon and gastric carcinomas and the DPC gene, associated with pancreatic cancer.

--------------------------------------------------------------------------------18>

The correct answer is D. Perforation of a peptic ulcer is potentially fatal, because of either peritonitis with sepsis or sudden exsanguination (if the

perforation damages one of the many arteries of the stomach). Peptic ulcer disease, gastritis, and possibly gastric carcinoma and gastric lymphoma have

been strongly associated with Helicobacter pylori colonization of the mucus layer covering the gastric mucosa. Colonization is associated with destruction

of the mucus layer, thereby destroying its p rotective function.

Cryptosporidium parvum (choice A) causes diarrhea that is severe in immunocompromised patients.

Entamoeba histolytica (choice B) produces dysentery-like symptoms or can cause liver abscess.

Escherichia coli (choice C) causes a variety of diarrheal diseases and can infect the bladder and soft tissues.

Mycobacterium tuberculosis (choice E) causes tuberculosis, characterized by granuloma formation, especially in the lungs.

--------------- --------------- -------------- ---------------- --------------- -----19>The correct answer is E. By the third week of development, hematopoiesis

begins in the blood islands of the yolk sac. Beginning at 1 month of age and continuing until 7 months of age, blood elements are also formed in the

liver. Hematopoiesis occurs in the spleen and lymphatic organs between 2 and 4 months, and in the bone marrow after 4 months.

--------------------------------------------------------------------------------

15>The correct answer is C. The patient is suffering from schizophrenia. The key to the d iagnosis of psychosis is that there has been a marked decline

in the level of functioning (i.e., the man is homeless and cannot care for himself). Although hallucinations or delusions are not mentioned in the case

history, the presence of disorganized speech, grossly disorganized behavior, and the duration of symptoms (longer than six months) suggest a diagnosisof schizophrenia.

In schizoaffective disorder (choice A), alterations in mood are present during a substantial portion of the illness.

Although schizoid personality disorder (choice B) produces detachment from social relationships and is characterized by restriction of emotional

expression, it is not accompanied by a marked decline in occupational functioning.

Schizophreniform disorder (choice D) is characterized by schizophrenic-like symptoms, but the duration o f symptoms is, by definition, less than six

months.

Schizotypal personality disorder (choice E) is characterized by eccentricities of behavior, odd beliefs or magical thinking, and difficulties with social and

interpersonal relationships. Unlike schizophrenia, schizotypal personality disorder is not characterized by a formal thought d isorder.

--------------------------------------------------------------------------------

--------------- --------------- -------------- ---------------- --------------- -----21>The correct answer is E. Familial hypercholesterolemia, which is due to

defective function of the LDL receptor, is an area of intense research. The molecular basis of LDL receptor abnormalities is becoming better understood,

and more than 200 mutations in the gene for the LDL receptor have been identified. The gene has 5 general domains and 18 exons. Defects near exons

7 to 14 (including this case) are in the region of homology with epidermal growth factor receptor precursor. This region of the molecule is needed for

dissociation of LDL from the receptor in the endosome. Receptors with a defect in this area (sometimes called class II mutations) also have trouble

being initially transported to the Golgi complex (transport-deficiency alleles) and become trapped in endoplasmic reticulum.Decreased transcription of the LDL receptor gene (choice A) is considered a class I mutation and involves the signal sequence domain near exon 1.

Poor internalization of LDL bound to LDL receptor (choice B) is considered a class IV mutation. Such mutations are associated with the membrane-

spanning/cytoplasmic domain, specifically near exon 18.

Poor retention of the LDL receptor in the membrane (choice C) is considered a class IV mutation and is associated with the membrane-

spanning/cytoplasmic domain, specifically near exons 2-6.

Reduced binding of LDL (choice D) is considered a class III mutation and involves the LDL binding domain near exons 2-6.

--------------- --------------- -------------- ---------------- --------------- -----22>The correct answer is D. Respiratory distress immediately follows amniotic

fluid embolism as the emboli consisting of squamous cells, lanugo, and mucus deposit in the pulmonary microcirculation, producing numerous tiny

pulmonary infarcts. The dramatic respiratory distress may also reflect the action of prostaglandins and other bioactive compounds present in high

concentrations in the amniotic fluid embolus.

Hemiplegia (choice A) would reflect an ischemic injury to one hemisphere of the cerebrum or the brainstem. A venous embolus would not produce such

an insult.

Placental abruption (choice B) is partial, premature separation of the placental disc from the endometrium. Although abruption may occur in this setting,

it is not a result of an amniotic fluid embolism.

There are numerous causes of renal failure (choice C); the most likely ones in the peripartum interval include eclampsia, hypovolemic shock, and

ascending infections. Amniotic fluid embolism would be expected to produce severe dyspnea well before shock and renal failure might arise.

Splinter hemorrhages (choice E) are small hemorrhages seen on toes and fingers due to a shower of microemboli arising in the arterial circulation.Amniotic fluid emboli arise in the veins and deposit in the lungs.

--------------- --------------- -------------- ---------------- --------------- -----23>The correct answer is D. The patient has a megaloblastic anemia, which can

be due to deficiency of folate or B12. Pregnancy increases the need for folate and other nutrients used by both baby and mother, and may "unmask" a

borderline dietary deficiency. For this reason, most obstetricians recommend vitamin supplements for pregnant women.

Ascorbic acid (choice A) is vitamin C, and its deficiency predisposes for capillary fragility and oral lesions.

Calcium deficiency (choice B) predisposes for osteoporosis/osteopenia.

Copper deficiency (choice C) is rare; when it occurs, it may cause a hypochromic anemia, neutropenia, osteoporosis, or hypotonia.

Iron deficiency (choice E) causes a microcytic, hypochromic anemia, with reduced mental and physical performance.

--------------- --------------- -------------- ---------------- --------------- -----24>The correct answer is D. The lesions are characteristic of molluscum

contagiosum, which is a typically benign and self-limited condition caused by a poxvirus. The disease can be transmitted either venereally or through

non-venereal contact. The other viruses listed do not cause similar skin lesions. Patients with advanced HIV infection may develop a severe, generalized,

and persistent eruption, often involving the face and upper body.

Cytomegalovirus (choice A) causes congenital infections and d isseminated infections in immunosuppressed patients.

Herpesvirus 6 (choice B)causes roseola (exanthem subitum).


13 6/26/2011


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Parvovirus (choice C) causes aplastic crises in patients with hemolytic anemia.

Variola (choice E) is the smallpox virus.

--------------- --------------- -------------- ---------------- --------------- -----25>The correct answer is D. This is a relatively simple question that requires you

to visualize the relationship among the key parts of the kidney and to identify the one that lies most medially. If you think about it for a second, since

the kidneys ultimately drain into the ureter at their medial poles, you are looking for the structure that is closest to the ureter. The correct answer is the

renal pelvis. The renal pelvis is the dilated upper po rtion of the ureter that receives the major calyces.

In terms of the other answer choices, the order from most lateral to most medial is: renal cortex (choice C), renal pyramid (choice E), minor calyx

(choice B), major calyx (choice A), and then the renal pelvis (choice D).

--------------------------------------------------------------------------------

26>

The correct answer is A. Cyclophosphamide is metabolized to acrolein, which is excreted in the urine. If the patient's urine is concentrated, the toxic

metabolite may cause severe bladder damage. Early symptoms of bladder toxicity include dysuria and frequency. This can be distinguished from a

urinary tract infection, since there is no bacteriuria with cyclophosphamide-induced bladder toxicity. However, microscopic hematuria is often present onurinalysis. In severe hemorrhagic cystitis, large segments of the bladder mucosa may be shed which can lead to prolonged, gross hematuria. The

incidence of cyclophosphamide-induced hemorrhagic cystitis can be decreased by ensuring that the patient maintains a high fluid intake.

Cyclophosphamide is an alkylating agent used in the treatment of breast carcinoma, malignant lymphoma, multiple myeloma, and adenocarcinoma of the

ovary, as well as various other forms of cancer. The major toxic reactions commonly seen with this agent include mucositis, nausea, hepatotoxicity,

sterile hemorrhagic and non-hemorrhagic cystitis, leukopenia, neutropenia, and interstitial pulmonary fibrosis.

Mitomycin (choice B) is an antibiotic antineoplastic agent used in the treatment of breast carcinoma, adenocarcinoma of the pancreas and stomach, as

well as various other forms of cancer. The major toxic reactions commonly seen with this agent include bone marrow depression, nausea, hepatotoxicity,

acute bronchospasm, thrombocytopenia, and interstitial pneumonitis.

Paclitaxel (choice C) is an antineoplastic agent primarily used in the treatment of ovarian and breast cancer. The major toxic reactions commonly seen

with this agent include bone marrow depression, nausea, hepatotoxicity, bronchospasm, thrombocytopenia, and neutropenia.

Tamoxifen (choice D) is an antineoplastic hormone primarily used in the palliative treatment of estrogen-receptor positive breast cancer patients. The

major toxic reactions commonly seen with this agent include depression, dizziness, thrombosis, mild leukopenia or thrombocytopenia.

Vincristine (choice E) is a mitotic inhibitor antineoplastic agent used in the treatment of breast cancer, Hodgkin's disease, non-Hodgkin's lymphoma,

advanced testicular cancer and various other types of cancer. The major tox ic reactions commonly seen with this agent include mental depression,

hemorrhagic enterocolitis, bone marrow depression, nausea, thrombocytopenia, and leukopenia

--------------- --------------- -------------- ---------------- --------------- -----27>The correct answer is A. In a syndrome called cleidocranial dysostosis,

absence of part of the clavicles accompanies a broad skull, and facial and dental anomalies. Note that you could also have answered this question bynoting that of the bones listed, only the clavicles form by intramembranous ossification.

The femurs (choice B), metatarsals (choice C), phalanges (choice D), and tibias (choice E) are cartilaginous (formed by endochondral ossification) rather

than membranous bones.

--------------- --------------- -------------- ---------------- --------------- -----28>The correct answer is D. The tumor is a neuroblastoma, which is one of the

principal forms of cancer in children. Neuroblastoma typically occurs before age 5, with many presenting before age 2 . Neuroblastoma can arise from

neural crest cells throughout the body, but the adrenal medulla is the most common site. Homer-Wright pseudorosettes are circles of tumor cells with

central young nerve fibers arising from the tumor cells. The oncogene associated with neuroblastoma is N-myc.

erb-B2 (choice A) is associated with breast, ovarian, and gastric carcinomas.

c-myc (choice B) is associated with Burkitt's lymphoma.

L-myc (choice C) is associated with small cell carcinoma of the lung.

ret (choice E) is associated with multiple endocrine neoplasia, types II and III.

--------------- --------------- -------------- ---------------- --------------- -----29>The correct answer is B. The disease is von Hippel-Landau disease, which is

associated with a deletion involving the VHL gene on chromosome 3 (3p). Affected individuals develop vascular tumors (hemangioblastomas) of the

retina, cerebellum, and/or medulla. Roughly half of the affected individuals later develop multiple, bilateral renal cell carcinomas.

Berry aneurysms (choice A) are unrelated to hemangioblastomas, but are instead associated with adult polycystic disease.

Peripheral nerve cancers (choice C) are a feature of von Recklinghausen's disease (neurofibromatosis type I).

Choreiform movements, related to decreased GABA and acetylcholine (choice D), are a feature of Huntington's disease.Extremely high serum cholesterol (choice E) suggests the homozygous form of familial hypercholesterolemia.

--------------- --------------- -------------- ---------------- --------------- -----30>The correct answer is A. The space constant of an axon reflects the amount

of passive or electrotonic spread of current within an axon. The larger the space constant, the further the current can spread, allowing action potentials

to propagate faster. This is why myelin increases the conduction velocity of action potentials down an axon. Conversely, demyelination decreases the

space constant and slows action potential conduction.

--------------- --------------- -------------- ---------------- --------------- -----31>The correct answer is A. Coarctation of the aorta occurs in two patterns. In

the infantile type, the stenosis is proximal to the insertion of the ductus arteriosus (preductal); this pattern is associated with Turner's syndrome. In the

adult form, the stenosis is distal to the ductus arteriosus (postductal) and is associated with notching of the ribs (secondary to continued pressure from

the aorta on them), hypertension in the upper extremities, and weak pulses in the lower extremities. Headache, cold extremities, and lower extremity

claudication with exercise are typical if the patient is symptomatic (many adults with mild distal coarctation may remain asymptomatic for years). Upper

extremity hypertension with weak pulses in the lower extremities, and a midsystolic (or continuous) murmur over the chest or back may be the only

obvious signs in some. Note that the chronic cough is probably related to the man's smoking, and is not caused by the coarctation.

Eisenmenger's syndrome (choice B) is a shift from a left-to- right shunt to a right-to- left shunt secondary to pulmonary hypertension.

Tetralogy of Fallot (choice C) and transposition of great arteries (choice D) cause cyanosis and are usually diagnosed in infancy.

Ventricular septal defect (choice E) might remain undiagnosed until adulthood, but would not cause notching of the ribs.

--------------- --------------- -------------- ---------------- --------------- -----32>The correct answer is C. The muscularis of the upper third of the esophagus

(choice E) is composed entirely of striated muscle. The middle third (choice C) contains both striated and smooth muscle. The lower third (choice B) andlower esophageal sphincter (choice A) contain only smooth muscle. There is no such thing as the upper esophageal sphincter (choice D).

--------------- --------------- -------------- ---------------- --------------- -----33>The correct answer is A. Bilirubin is a degradative product of hemoglobin

metabolism. Bilirubin (pigment) stones are specifically associated with excessive bilirubin production in hemolytic anemias, including sickle cell anemia.

Bilirubin stones can also be seen in hepatic cirrhosis and liver fluke infestation.

Calcium oxalate stones (choice B) and cystine stones (choice E) are found in the kidney, rather than the gallbladder.

Pure cholesterol stones (choice C) are less common than mixed gallstones, but have the same risk factors, including obesity and multiple pregnancies.

Mixed stones (choice D) are the common "garden variety" gallstones, found especially in obese, middle aged patients, with a female predominance

--------------------------------------------------------------------------------

34>

The correct answer is A. Malnutrition associated with chronic alcoholism can lead to a severe magnesium deficiency. The effect of low serum magnesium

on parathyroid hormone secretion (PTH) depends on severity and duration. An acute decrease in serum magnesium will increase PTH secretion, while a

prolonged severe deficiency results in decreased PTH secretion. There is also evidence that the action of PTH is decreased with chronic magnesium

deficiency. Hence, this patient is suf fering from "functional" hypoparathyroidism. The low serum calcium can produce weakness, tremors, muscle

fasciculations, and seizures. A positive Trousseau's sign indicates the presence of latent tetany. It is observed by inflating a blood pressure cuff above


13 6/26/2011


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systolic blood pressure for at least 2 minutes. A positive reaction consists of the development of carpal spasm, with relaxation occurring within seconds

after deflating the cuff. In patients with magnesium deficiency, magnesium administration will produce a prompt rise in plasma PTH with subsequent

restoration of serum calcium concentration to normal.

With functional hypoparathyroidism bone density would be decreased (not increased, choice C).

The combination of decreased PTH secretion (not increased, choice D) and decreased effectiveness of PTH produce hypocalcemia and

hyperphosphatemia (not hypophosphatemia, choice B).

Urinary cAMP would probably be decreased (not increased, choice E), given the low PTH.

--------------- --------------- -------------- ---------------- --------------- -----35>The correct answer is E. Enteropeptidase, formerly called enterokinase,

activates trypsinogen by limited proteolytic digestion to give trypsin. Trypsin is itself capable of activating trypsinogen, which produces a positive

feedback effect. Trypsin also activates chymotrypsinogen (and several other proteolytic enzymes), so deficiency of enteropeptidase results in a severe

deficiency of enzymes that digest protein.

Amylase (choice A) aids in the breakdown of starches to oligosaccharides, maltose, and maltotriose.

Colipase (choice B), along with other lipases, functions to digest fats.Lactase (choice C) is a brush-border disaccharidase that hydrolyzes the bond between galactose and glucose in lactose.

Pepsin (choice D) is a proteolytic enzyme secreted in an inactive form (pepsinogen) by the chief cells of the stomach. Pepsinogen is activated by

stomach acid, and so is not dependent on enteropeptidase. Pepsin alone will not replace the activities of other proteolytic enzymes, partly because food

does not remain in the stomach for an extended period of time.

--------------- --------------- -------------- ---------------- --------------- -----36>The correct answer is E. The child is likely suffering from cystic fibrosis. In

this disorder, an abnormality of chloride channels causes all exocrine secretions to be much thicker, and more viscous than normal. Pancreatic secretion

of digestive enzymes is of ten severely impaired, with consequent steatorrhea and deficiency of fat-soluble vitamins, including vitamin A.

Cystinuria (choice A) is a relatively common disorder in which a defective transporter for dibasic amino acids (cystine, ornithine, lysine, arginine; COLA)

leads to saturation of the urine with cystine, which is not very soluble in urine, and precipitates out to form stones.

Hypoglycemia (choice B) is not a prominent feature of children with cystic f ibrosis who are on a normal diet. Hyperglycemia may occur late in the course

of the d isease.

Iron deficiency anemia (choice C) is not found with any regularity in children with cystic fibrosis.

Sphingomyelin accumulation (choice D) is generally associated with deficiency of sphingomyelinase, as seen in Niemann-Pick disease.

--------------

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