Sickle Cell Anemia

Gregg Selke, Ph.D.

11/28/06

What is Sickle Cell Anemia (SCA)? First described in Chicago in

1910 by James Herrick as an inherited condition that results in a decrease in the ability of red blood cells to carry oxygen throughout the body

Sickle red blood cells become hard and irregularly shaped (resembling a sickle)

Become clogged in the small blood vessels and therefore do not deliver oxygen to the tissues.

Lack of tissue oxygenation can cause excruciating pain, damage to body organs and even death.

Mechanism

Red blood cells (RBC)

Contain a special protein called haemoglobin

(Hb) Hb is the component that carries oxygen

from the lungs to all parts of the body

Most people have only hemoglobin type – Hb

A within RBC (normal genotype: Hb AA)

Sickle Cell: HbS

S similar to A, but one structural change

Other types: HbC, HbD, and HbE

Mechanism -HbS

When sickle haemoglobin (HbS) gives up its oxygen to the tissues, HbS sticks together Forms long rods form inside RBC RBC become rigid, inflexible, and sickle-shaped Unable to squeeze through small blood vessels,

instead blocks small blood vessels Less oxygen to tissues of body

RBCs containing HbS have a shorter lifespan Normally 120 days Chronic state of anaemia

Genetics 2 copies of the

gene for Hb (each parent)

HbS –Recessive S=Sickle A=Normal

Sickle Cell Trait

Sickle haemoglobin (S) + Normal haemoglobin (A) in RBC Adequate amount of normal Hb (A) in red blood

cells RBC remain flexible Carrier Do Not have the symptoms of the sickle cell

disorders, with 2 exceptions

1. Pain when Less Oxygen than usual (scuba diving, activities at high altitude (12,000ft), under general anaesthesia)

2. Minute kidney problems

1. Sickle Cell Anemia Sickle haemoglobin (HbS) + Sickle haemoglobin

(HbS)

Most Severe – No HbA

Three common types of Sickle Cell Disorders

Other Sickling DisordersOther types of Hb combine with sickle Hb

2. Hemoglobin S-C disease Sickle haemoglobin (HbS) + (HbC)

3. Hemoglobin S-Beta thalassemia Beta thalassaemia gene reduces the

amount of HbA that can be made Sickle haemoglobin (HbS) + reduced HbA Milder form of Sickle Cell Disorder than

sickle cell anemia

Some Genetic History

The error in the hemoglobin gene results from a genetic mutation that occurred many thousands of years ago in people in parts of Africa, the Mediterranean basin, the Middle East, and India.

A deadly form of malaria was very common at that

time Malaria epidemics caused the death of many In areas where malaria was a problem, children who

inherited one sickle hemoglobin gene and who, therefore, carried the sickle cell trait - had a survival advantage.

Unlike the children who had normal hemoglobin genes, they survived the malaria epidemics they grew up, had their own children, and passed on the gene- for sickle hemoglobin.

Sickle Cell Gene Severe Malaria

As populations migrated, the sickle cell-mutation spread to other Mediterranean areas, further into the Middle East and eventually into the Western Hemisphere.

In the United States and other countries where malaria is not a problem, the sickle hemoglobin gene no longer provides a survival advantage.

Instead, it may be a serious threat to the carrier's children, who may inherit two abnormal sickle hemoglobin genes and have sickle cell anemia.

History

Most common in Africans and African Americans.

East Asia, Southern Italy, Saudi Arabia, India, Egypt, South and Central American, Cuba, the Caribbean, Greece, and Iran, and Eastern Jews have also been found to have a form of this illness.

Who is at risk?

Prevalence

More than 2.5 million Americans have the trait

70,000 or more Americans have sickle cell disease

About 1,000 babies are born with the disease each year in America In Nigeria, 1/3 population of U.S., 45,000-90,000

babies with sickle cell disease are born each year

Among African - Americans 1 in 12 have Sickle Cell Trait (Hb SA)

1 in 600 have Sickle Cell Anemia (Hb SS)

1 in 1500 have Sickle C Disease (Hb SC)

1 in 350 have Sickle Cell Disease (Hb SS, SC, S-Beta-Thal)

Among Latinos 1 in 172 have Sickle Cell Trait (Hb AS)

1 in 1,000 have Sickle Cell Disease (Hb SS, SC, S-Beta-Thal)

Screening

1. Haemoglobin Electrophoresis Simple Blood test Routine screening in high risk groups

• During pregnancy• Before anaesthesia

2. Prenatal Testing Amniocentesis

16 and 18 weeks of the pregnancy small risk of causing a miscarriage (1 in 100)

Chorionic villus sampling (CVS) 9th or 10th week of pregnancy very small amount of material from the developing

placenta slightly higher chance of miscarriage

Early Symptoms and Complications

Typically appear during infant's first year 1st symptom: dactylitis and fever (6 mo-2

yrs) Pain in the chest, abdomen, limbs and

joints Enlargement of the heart, liver and spleen

nosebleeds Frequent upper respiratory infections Chronic anemia as children grow older

Over time Sickle Cell sufferers can experience damage to organs such as liver, kidney, lungs, heart and spleen

Can result in death

Medical Complications

1. pain episodes

2. strokes

3. increased infections

4. leg ulcers

5. bone damage

6. yellow eyes or jaundice

7. early gallstones

8. lung blockage

9. kidney damage and loss of body water in urine

10.painful erections in men (priapism)

11.blood blockage in the spleen or liver (sequestration)

12.eye damage

13.low red blood cell counts (anemia)

14.delayed growth

Infectious complications Prominent early in life Leading cause of morbidity and mortality Great improvement in the prognosis related to newborn

screening for sickle cell disease, vaccination for childhood illnesses, the use of prophylactic antibiotics, and aggressive diagnosis and treatment of febrile events

Acute splenic sequestration Episodes of rapid increase in splenic size and decrease

in hemoglobin Potential source of morbidity and mortality early in life

for children with sickle cell anemia and at any age for those with Hb SC disease and sickle thalassemia

Serious Complications

Strokes Up to 15% of children may have overt or silent strokes

during childhood Chronic transfusion therapy reduces the recurrence

rate of overt stroke which may approach 75% without intervention

Bone disease Early risk is primarily from osteomyelitis

Infectious usually painful inflammatory disease of bone often of bacterial origin and may result in bone tissue death

Avascular necrosis of the femur and humerus Death of bone tissue due to disrupted blood

supply Marked by severe pain in the affected region and

by weakened bone that may flatten and collapse

Serious Complications

Serious Complications

Leg ulcers Seen in patients older than 10 years of age Resistant to therapy and cause significant morbidity

Ophthalmic complications Proliferative retinopathy, vitreous hemorrhage, & retinal

detachment

Priapism Distressing complication that occurs at all ages Difficult to treat Causes a high incidence of impotence

Chronic Anemia Associated with fatigue, irritability, jaundice, pain, delayed

puberty, leg sores, eye problems, gum disease

Serious Complications: PAINRecurrent Pain Episodes or Sickling

Crises Occur at any age but appear to be

particularly frequent during late adolescence and early adult life Unpredictable Red Blood Cells get stuck in the small veins

and prevent normal blood flow Characterized by severe severe pain in the back,

chest, abdomen, extremities, and head Highly disruptive to life Most common reasons for individuals to seek

health care

1. Fever

2. Chest pain

3. Shortness of Breath

4. Increasing tiredness

5. Abdominal swelling

6. Unusual headache

Danger Signs of a Crisis

7. Any sudden weakness orloss of feeling

8. Pain that will not go away with home treatment

9. Priapism (painful erection that will not go down)

10.Sudden vision changeSEEK URGENT HOSPITAL TREATMENT IF IN CRISIS

Crises

During a crisis severe pain in the fingers, toes,

arms, joints,legs, back, abdomen, and bones.

Decrease in oxygen to the chest and lungs May lead to acute chest syndrome

Damage to the lungs Severe pain and fever Lungs' airways narrow, further reducing

O2

Leads to an increased risk of potentially fatal infections

Infections Thirst and dehydration caused by not

drinking enough even if thirst is not felt Over-exertion Over-excitement Cold weather and cold drinks and

swimming Bangs, bumps, bruises and strains Stress triggers pain in adults, but does

not seem to do so in children.

Triggers of Pain

Children and families can often tell when a severe sickle pain is coming on by

Thirst

Eyes turning yellow (jaundice),

Sufferer being more irritable or tired than usual.

Predicting Pain

Alleviating Pain

Warmth: increases blood flow Massaging and rubbing Heat from hot water bottles and deep heat creams Bandaging to support the painful region Resting the body Cognitive Behavioral Therapy Getting the sufferer to relax

deep breathing exercises distracting the attention by other psychological methods.

Pain-killing medicines (analgesics): paracetamol, codeine non-steroidal anti-inflammatory, morphine if necessary

1. Taking the folic acid (folate) daily to help make new red cells

2. Daily penicillin until age six to prevent serious infection

3. Drinking plenty of water daily (8-10 glasses for adults)

4. Avoiding too hot or too cold temperatures

5. Avoiding over exertion and stress

6. Getting plenty of rest

7. Getting regular check-ups from knowledgeable health care providers

Daily Preventative Measures

Treating Complications

Pain-killing drugs and oral and intravenous fluids To reduce pain and prevent complications.

Transfusions Correct anemia Treat spleen enlargement in children before the

condition becomes life-threatening Regular transfusion therapy also can help prevent

recurring strokes in children at high risk of crippling nervous system complications.

Psychosocial Issues

Require regular medical attention Especially before and after operations, dental

extraction and during pregnancy. Adherence to medical regimen

Vitamins, antibiotics, fluid intake, activity level Schools must be involved Family planning Suitable types of employment Air travel

Increased fluids, pain killers or oxygen may be recommended

Child should be encouraged to participate in sports, but not pushed passed their limitations If they are in pain or feel tired they should be

allowed to rest and keep warm. They should have access to drinks. Strenuous exercise, dehydration and cold can

induce a crisis. Strenuous outdoor activities should be avoided in

cold or wet weather Should only swim if the water is warm and care is

taken to keep warm when leaving the water If develops a crisis despite these precautions he or

she should avoid swimming all together

Psychosocial Issues

Child Specific Issues: Coping with Pain Pain happens more often

On an average of one third of all days Lasts longer

Generally all day, even if not continuously all day

Associated with great tiredness about half the time

Causes them to spend significant time in bed On average the time spent wholly or partly in

bed adds up to about a week of every school term.

Psychosocial Issues

Variability and Unpredictability Some are mildly affected and largely free from

pain, while others have frequent and severe pain Most children go through good and bad patches Doctors cannot predict who will be severely

affected.

No easily overt detectable signs of sickle pain So children known to have sickle cell disorder

who say they are in pain must be trusted If they can rely on the adults around them to

take them seriously, they are less likely to take advantage of their condition to seek attention or avoid distasteful tasks.

Psychosocial Issues

To reduce risk of crisis, children are encouraged to drink much more than normal and more frequently May require about 1/4 litre of liquid every 60 -

90 minutes. Child will need to go to the toilet more

frequently May increase risk of Enuresis

Boys at risk for priapism May be too embarrassed to mention to parents Severe sickling can lead to impotence

Psychosocial Issues

Hydroxyurea The first effective drug treatment for adults with

severe sickle cell anemia reported in early 1995 Daily doses of the anticancer drug,

hydroxyurea, reduced the frequency of painful crises, acute chest syndrome, needed fewer blood transfusions

Increases production of fetal hemoglobin in the blood Fetal hemoglobin seems to prevent sickling

of red cells cells containing fetal hemoglobin tend to

survive longer in the bloodstream

Developing Treatments

Bone marrow transplantation

Shown to provide a cure for severely affected children with sickle cell disease

Only about 18 percent of children with sickle cell anemia are likely to have a matched sibling.

Developing Treatments

The Ultimate Cure? Gene Therapy

1. Correcting the “defective gene” and inserting it into the bone marrow

2. Turning off the defective gene and simultaneously reactivating another gene that turns on production of fetal hemoglobin.

No real cure for Sickle Cell Anemia at this time.

“In the past 30 years, the life expectancy of people with sickle cell anemia has increased. Many patients with sickle cell anemia now live into their mid-forties and beyond.”

Websiteshttp://www.sicklecellsociety.org/ : Another Great Siteinformation, Counselling and Caring for those with Sickle Cell Disorders and their families: UK based

http://www.sicklecelldisease.org/: Sickle Cell Disease Association of America

The Human Genome Project Sickle Cell Education Site at http://www.massinteraction.org/html/genome/

http://www.ascaa.org/ American Sickle Cell Anemia AssociationASCAA was founded in 1971 and is the oldest sickle cell research, education, and social services organization in the United States.

http://www.ncd.gov/

http://www.painfoundation.org/

 

Sites for Kids

http://www.sicklecellsociety.org/sicklescene/pshomf.htm Planet Sickle Cell Society (UK based)-Youth support, Poetry, Pen-Pals, Information, Message

Board

http://www.starbright.org/The STARBRIGHT Foundation is dedicated to the development of projects that empower seriousl ill children to combat the medical and emotional challenges they face on a daily basis.

Coloring Books on Sickle Cell from Emory:http://www.emory.edu/PEDS/SICKLE/bbc/index.htmhttp://www.emory.edu/PEDS/SICKLE/chelate/index.htm

Support Group Information:

Florida, Jacksonville: Sickle Cell Support Groups (904) 549-4472

Georgia, Atlanta: Parent SC Support Group (404) 616-4395