Lipid storage myopathies. A review of metabolic defect and of treatment.

Various cases of lipid storage myopathies have been described. The biochemical defect could be determined in only some of these cases. The syndromes identified to date are as follows: carnitine deficiency (type I lipid storage myopathy), carnitine-palmityltransferase (CPT) deficiency and pyruvate-decarboxylase deficiency. In the last two diseases the vacuolization in muscle is not marked. The case of a 10 year old carnitine deficient patient with a history of insidious muscle weakness in the proximal limb and neck muscles is presented. The patient was treated with oral carnitine and a medium chain triglyceride diet for 18 months and her clinical status has remained improved. In other lipid storage patients prednisone treatment resulted in improvement. In cases of suspected lipid storage myopathy the following studies are indicated: 1) examination of ketone bodies in serum and urine during fasting, long chain and medium chain triglyceride diets; 2) serum triglyceride and serum carnitine; 3) study on fresh muscle and fibroblasts with labeled substrates, biochemical determination of carnitine and CPT in muscle.