Lipid storage myopathy with normal carnitine levels

Abstract

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-μm 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.