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Glycogen storage disease
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Glycogen storage disease (gsd)

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Glycogen storage disease (gsd)

  1. 1. Glycogen storage disease (gsd)<br />Saddam Ansari<br />Tbilisi State Medical University<br />4th May 2011<br />
  2. 2. Introduction<br />Glycogen is a branched-chain polymer of glucose and serves as a dynamic but limited reservoir of glucose, mainly in skeletal muscle and liver.<br />There are a number of different enzymes involved in glycogen synthesis, utilization and breakdown within the body.<br />
  3. 3. Continued…<br />Glycogen storage disorders (GSD) are a group of inherited inborn errors of metabolism due to deficiency or dysfunction of these enzymes.<br />confined to just liver and muscle<br />But some cause more generalised pathology and affect tissues such as the kidney, heart and bowel. <br />The classification of glycogen storage disorders is based on the enzyme deficiency and the affected tissue.<br />
  4. 4.
  5. 5. Epidiomology<br />The overall GSD incidence is estimated at 1 case per 20,000-43,000 live births.<br />Type I is the most common (25% of all GSD).<br />
  6. 6. Inheritance patterns<br />Autosomal recessive (I, II, III, IV, V, VII, some IX). <br />Both parents are carriers. <br />Chance of sibling being affected is 1 in 4.<br />X-linked (some IX, VI)<br />
  7. 7. Types <br />There are eleven (11) distinct diseases that are commonly considered to be glycogen storage diseases <br />Although glycogen synthase deficiency does not result in storage of extra glycogen in the liver, it is often classified with the GSDs as type 0.<br />
  8. 8. Type I, Von Gierke's disease<br />Affected enzyme: glucose-6-phosphatase<br />Affected tissue: Liver and kidney <br />Clinical features:<br />Large quantities of glycogen are formed and stored in hepatocytes, renal and intestinal mucosa cells. The liver and kidneys become enlarged.<br />
  9. 9. Abnormalities of lipids may lead to xanthoma formation.<br /> Uric acid is often elevated and may cause clinical gout. Galactose, fructose, and glycerol are metabolised to lactate. The elevated blood lactate levels cause metabolic acidosis.<br />
  10. 10. Treatment <br />Blood loss may require oral iron.<br />Raised uric acid levels may require allopurinol.<br />Treatment of hyperuricaemia and pyelonephritis protect renal function.<br />Diazoxide to maintain blood glucose has been disappointing.<br />Liver transplantation for primary disease or for hepatocellular carcinoma seems effective.<br />
  11. 11. Type II, Pompe's disease <br />Cause: <br />The deficiency of the lysosomal enzyme alpha-1,4-glucosidase (acid maltase) leads to the accumulation of glycogen in many tissues.<br />Clinical feature:<br />The clinical spectrum is continuous and broad, with presentation in infants, children and adults.<br />In the infantile form, accumulation of glycogen in cardiac muscle leads to cardiac failure.<br />
  12. 12. Accumulation may also occur in the liver, which results in hepatomegaly and elevation of hepatic enzymes.<br />Glycogen accumulation in muscle and peripheral nerves causes hypotonia and weakness.<br />Glycogen deposition in blood vessels may result in intracranial aneurysms.<br />
  13. 13. Treatment:<br />Enzyme replacement therapy (Alglucosidasealfa)<br />Diet therapy may provide temporary improvement but does not alter the disease course: a high-protein, low-carbohydrate diet may be beneficial.<br />Physiotherapy and occupational therapy may be required.<br />
  14. 14. Genetic counselling and prenatal diagnosis: chorionic villus sampling and amniocentesis can be used to determine enzyme activity in a fetus.<br />Gene therapy remains a potentially effective treatment for the future.<br />
  15. 15. Type III, Cori disease<br />Affected enzyme: Glycogen debranching enzyme. Deposition of abnormal glycogen structure.<br />Affected tissues: Liver and muscle.<br />Clinical features:<br />About 15% affect liver only. Hypoglycaemia, poor growth, hepatomegaly, moderate progressive myopathy.<br />Symptoms can regress with age.<br />A few cases of liver cirrhosis and hepatocellular carcinoma have been reported.<br />
  16. 16. Continued…<br />Treatment: As with type I, also protein supplements for muscle disorder. <br />
  17. 17. Type IV, Andersen's disease, Amylopectinosis<br />Affected enzyme: Glycogen branching enzyme. Abnormally structured glycogen forms.<br />Affected tissues: Many, including liver. Rare variant affects peripheral nerves.<br />Clinical features:<br />Hepatomegaly, failure to thrive, cirrhosis, splenomegaly, jaundice, hypotonia, waddling gait, lumbar lordosis.<br />
  18. 18. Continued…<br />Treatment: Liver transplant.<br />Prognosis: Mostly death by age 4 due to cirrhosis and portal hypertension.<br />
  19. 19. Type V, McArdle's disease<br />Cause: Myophosphorylase deficiency<br />Affected tissue: Muscle<br />Clinical features<br />Clinical findings may be absent on physical examination. Muscle strength and reflexes may be normal<br />In later adult life, persistent proximal weakness and muscle wasting may be present.<br />
  20. 20. The fatal infantile form presents with hypotonia and reduced reflexes.<br />Ischaemic forearm test: traditional test but is painful and non-ischaemic exercise tests are now preferred.<br />
  21. 21. Treatment <br />No specific treatment exists.<br />Avoid strenuous (anaerobic or sustained) exercise, including lifting or pushing.<br />A carbohydrate rich diet did benefit patients.<br />
  22. 22. Type VI, Hers disease<br />Affected enzyme: Liver phosphorylase.<br />Affected tissues: Liver, rare cardiac form.<br />Clinical features:<br />Most common variant is X-linked therefore usually affects only males.<br />Hepatomegaly, hypoglycaemia, growth retardation, hyperlipidaemia.<br />
  23. 23. Continued…<br />Treatment: Cardiac transplantation for rare cardiac form. May need frequent feeding to avoid hypoglycaemia.<br />Prognosis: Usually normal life span.<br />
  24. 24. Type VII, Tarui disease<br />Cause: Phosphofructokinase (PFK) deficiency<br />Affected tissue: Muscle<br />Clinical features:<br />Exercise intolerance, muscle cramping, exertionalmyopathy, compensated haemolysis and myoglobinuria.<br />Note : Symptoms can be similar to McArdle's Glycogen Storage Diseasebut more severe.<br />
  25. 25. Treatment:<br />No specific treatment exists.<br />There is evidence that a high protein diet may improve muscle function and slow progression of the disease.<br />Vigorous exercise should be avoided as it causes myoglobinuria.<br />
  26. 26. Type XI, Fanconi-Bickel syndrome<br />Affected enzyme: Glucose transporter GLUT2[solute carrier family 2 ,facilitated glucose transporter]<br />Clinical features: Similar features to Von Gierke's disease, e.g. hypoglycaemia.<br />
  27. 27. Type 0, Lewis disease<br />Affected enzyme: Hepatic glycogen synthase.<br />Affected tissues: Liver. <br />Clinical features<br />Seizures can occur. <br />Fatigue and muscle cramps after exertion. <br />Mild growth retardation in some cases.<br />
  28. 28. Investigation <br />Blood tests:<br />Blood glucose: hypoglycaemia is likely<br />Liver function tests: monitoring for hepatic failure<br />Anion gap calculation: if glucose low, this may indicate lactic acidaemia<br />Urate<br />
  29. 29. Creatinine clearance<br />Creatine kinase<br />Full blood count<br />
  30. 30. Urine tests:<br />Myoglobinuria after exercise found in 50% of people with McArdle's disease.<br />
  31. 31. Imaging<br />Abdominal ultrasound scan: hepatomegaly<br />Echocardiography: to look for cardiac involvement in certain types of GSD<br />
  32. 32. Biopsy<br />Of liver.<br />Muscle or other tissues gives definitive diagnosis.<br />
  33. 33. Pre-natal diagnosis<br />Genetic counseling.<br />Referral to geneticist for possible prenatal investigation (amniotic fluid analysis) and diagnosis.<br />
  34. 34. Differential Diagnosis<br />In GSD affecting muscle, exclude the muscular dystrophies (including Duchenne's) and secondary disorders of muscle including polymyositis.<br />
  35. 35. Acknowledgement <br />
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