glycogen storage disorders
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Transcript of glycogen storage disorders
GLYCOGEN STORAGE
DISORDERSThese are a group of inherited disorders associated with glycogen metabolism, familial in incidence and characterized by deposition of normal or abnormal type and quantity of glycogen in the tissues
There are 6 classical types of glycogen
storage diseases
Type1)Von gierke’s disease
Type2)Pompe’s disease
Type3)Limit dextrinosis(Forbe’s disease)
Type4)Amylopectinosis(anderson’s disease)
Type5)McArdle’s disease
Type6)Her’s disease
TYPE 1:Von gierke’s disease
ENZYME DEFICIENCY :glucose-6-
phosphatase
INHERITANCE : Autosomal recessive
Liver cells and intestinal mucosal cells
are fully loaded with glycogen and
metabolically unavailable
CLINICAL AND BIOCHEMICAL FEATURES OF VON
GIERKE’S DISEASE
Only little amount of glucose is available is derived
from liver
So the children with this disease may tend to develop
hypogycemia
Fat is used as a energy source so it may lead to
LIPAEMIA,ACEDEMIA and KETOSIS
Excess of Acetyl coA is diverted for chosterol synthesis
this may lead to elevated level of cholestrol and
results in XANTHOMAS
Cont….
Increased fatty acid synthesis can produce fatty infiltration of liver
PERSISTENT HYPOGLYCAEMIA has 2 effects
Hypoglycemia inhibits insulin which in turn inhibits protein synthesis which results in DWARFISM
Hypoglycemia stimulates the secretion of CATECHOLAMINES which cause muscle glycogen to break down producing lactic acid and LACTIC ACIDOSIS
Increased blood lactic acid competes with urateexcretion by kidneys leading to increased blood uric acid levels
Children with increased uric acid synthesis may develop the symptoms of GOUT
PROGNOSIS
Children with this disease
may die young and some
of them survive till
adolescence
TYPE 2: POMPE’S DISEASE
ENZYME DEFICIENCY : ACID MALTASE enzyme which is present in lysosome and catalyses the
breakdown of oligosaccharides
INHERITANCE : AUTOSOMAL RECESSIVE
Here the glycogen structure is normal and the
organs which are involved is
HEART,LIVER,SMOOTH MUSCLE,AND STRAITED
MUSCLE
All the tissue contain excess of glycogen
CLINICAL FEATURES
Enlargement of heart (cardiomegaly)
Muscle weakness
PROGNOSIS
Infants usually die due to cardiac failure and broncho
pnuemonia
Death usually occurs before 9 months
TYPE 3 : LIMIT DEXTRINOSIS(FORBE’S
DISEASE)
ENZYME DEFICIENCY : DEBRANCHING ENZYME
INHERITANCE : AUTOSOMAL RECESSIVE
GLYCOGEN STRUCTURE : LIMIT DEXTRIN TYPE
Organs involved are heart liver and muscle
CLINICAL AND BIOCHEMICAL FEATURES
• HEPATOMEGALY
• MODERATE HYPOGLYCEMIA
• ACIDOSIS
• PROGRESSIVE MYOPATHY
• Enzyme deficiency can be
demonstrated in leucocytes
PROGNOSIS
Survives well to adultlife
TYPE 4 : AMYLOPECTINOSIS(ANDERSON’S
DISEASE)
ENZYME DEFICIENCY : BRANCHING ENZYME
INHERITANCE : NOT DEFINETELY KNOWN
Glycogen deposited is abnormal type, few
branch points and very long inner and outer
unbranched chains
LIVER is the mainly affected organ and other
organs are HEART, KIDNEY, and MUSCLES
Deposition is seen in RE SYSTEM
CLINICAL AND BIOCHEMICAL FEATURES
HEPATOMEGALY
SPLENOMEGALY
MODERATE HYPOGLYCEMIA
NODULAR CIRRHOSIS OF LIVER
HEPATIC FAILURE
Enzyme deficiency can be demonsrated in
leucocytes and liver
PROGNOSIS
Usually fatal
Longest survival is reported as 4 years
TYPE 5 : McArdle’s disease
ENZYME DEFICIENCY : MUSCLE PHOSPHORYLASE
INHERITANCE : AUTOSOMAL RECESSIVE
Glycogen deposited in normalstructure and the organs
involved are skeletal muscles
CLINICAL FEATURES
Muscle cramps on exercise
Pain
Stiffness and weakness of muscles
EPINEPHRINE TEST
After administration of epinephrine rise in
blood glucose occurs which shows that
hepatic phosphorylase activity is normal
TYPE 6 : Her’s disease
ENZYME DEFICIENCY : LIVER PHOSPHORYLASE
Glycogen deposited is normal in structure
Organs affected are mainly LIVERand LEUCOCYTES
CLINICAL AND BIOCHEMICAL FEATURES
HEPATOMEGALY
MODERATE HYPOGLYCEMIA
MILD ACIDOSIS