Lipid storage myopathy with normal carnitine levels.

A 28-year-old female, who showed a floppy baby syndrome during early infancy, had a non-progressive proximal muscle weakness with easy fatiguability since childhood. Two muscle specimens biopsied at the age of 28 years revealed myriads of 1-3-mum wide abnormal spaces containing neutral fat in type I and type II fibers. Both biopsies demonstrated a type I fiber preponderance. Electron microscopy demonstrated lipid excess and normal mitochondria by simple inspection. The mitochondrial area and sarcotubular membrane profile concentration in morphometry of longitudinal sections were also normal. Cross-sections, however, revealed a slight decrease of the individual mitochondrial size and of the sarcotubular membrane profile concentration . Serum and muscle carnitine levels and the muscle carnitine palmityltransferase level were all within normal range. Besides carnitine deficiency other biochemical defects can occur in lipid storage myopathy, which represents a syndrome rather than a unique disease entity.