Lipid Storage Myopathy Responsive to Prednisone

A 19-year-old girl had had slight muscle weakness before age 18. In her 19th year, she became progressively weaker and eventually bedfast; she then needed respiratory support. Results of liver function and blood coagulation studies were abnormal when the patient was at her weakest. An almost complete remission occurred after seven weeks of prednisone therapy (60 to 27.5 mg/ day); there was relapse 21 months later with lower dosages (10 to 20 mg/day). With higher dosages, the patient again improved but did not regain her strength fully. In three muscle biopsy specimens, there were myriads of abnormal spaces, especially in type I fibers, containing neutral fat and fatty acids. The histologic abnormalities were less marked during remission than just before the start of therapy or during relapse. The metabolic defect in the present case remains unidentified.