Pathology of skeletal muscle and intramuscular nerves in infantile neuroaxonal dystrophy

Biopsies of the biceps muscle and sural nerve were taken from a girl aged 2 years with infantile neuroaxonal dystrophy (INAD). In addition to the typical axonal spheroid bodies in a number of the i.m. nerve fibers, the neuromuscular junctions (NMJs) and motor nerve endings also contained axonal swellings. The sural nerve, except for three dystrophic fibers, was almost completely normal. A teased nerve preparation showed four additional abnormal fibers with focal axonal enlargement similar to those in giant axonal neuropathy (GAN). These results suggest that a biceps muscle biopsy may be more useful than a sural nerve biopsy for the diagnosis of INAD, because the muscle contains abnormal peripheral nerves and NMJs in high frequency.