Riboflavin-responsive lipid-storage myopathy and glutaric aciduria type II of early adult onset.

A 17-year-old girl with progressive lipid-storage myopathy for 2 years had low muscle carnitine levels. There was no therapeutic response to prednisone and DL-carnitine-HCl. Chemical findings indicated glutaric aciduria type II. Riboflavin therapy and a fat-restricted, carbohydrate-enriched diet resulted in dramatic improvement. Low carnitine concentrations in plasma and muscle were observed in three asymptomatic sisters who had normal urinary excretion patterns. There was impaired mitochondrial beta-oxidation in cultured skin fibroblasts from the index patient and all three siblings.