Ans. A. McArdle disease* McArdle disease is an AR condition, one of the type V glycogen storage disease.* Enzyme deficient: Myophosphorylase enzyme* Due to enzyme deficiency there is inability to breakdown the muscle glycogen and prevents lactate production.* Patients usually complain of exercise intolerance and muscle pain on exercise. Therefore strenuous exercise is contraindicated.Gycogen-storage diseasesTypeDefective enzymeOrgan affectedGlycogen in the affected organClinical featuresI. Von GierkeGlucose 6-phosphatase or transport systemLiver and kidneyIncreased amount; normal structureMassive enlargement of the liver. Failure to thrive, Severe hypoglycemia, ketosis, hyperuricemia, hyperlipemiaII. Pompea-1, 4-Glucosidase (lysosomal)All organsMassive increase in amount; normal structureCardiorespiratory failure causes death, usually before age 2III. CoriAmylo-1,6-glucosidase (debranching enzyme)Muscle and liverIncreased amount; short outer branchesLike type 1, but milder courseIV. AndersenBranching enzyme (a-1,4 - a -1,6)Liver and spleenNormal amount; very long outer branchesProgressive cirrhosis of the liver. Liver failure causes death, usually before age 2V. McArdlePhosphorylaseMuscleModerately increased amount; normal structureLimited ability to perform strenuous exercise because of painful muscle cramps. Otherwise patient is normal and well developedVI. HersPhosphorylaseLiverIncreased amountLike type 1, but milder courseVII.PhosphofructokinaseMuscleIncreased amount; normal structureLike type VVIII.Phosphorylase kinaseLiverIncreased amount; normal structureMild liver enlargement. Mild hypoglycemiaNote: Types I through VII are inherited as autosomal recessives. Type VIII is sex linked.