Peripheral nerve fibre changes in asymptomatic children of patients with familial amyloid polyneuropathy.

Sural nerve biopsies of 5 children of patients with familial amyloid polyneuropathy were studied by electronmicroscopy. The subjects were 14-17 years old and were in normal health. Neurological examination was negative. In none of the sural nerve specimens were there any amyloid deposits. In Case 4 no fine structural changes were detected. In the remaining 4 cases, there were frequent deposits of glycogen and clusters of multimembranous bodies in the Schwann-cell crescents of large myelinated fibres which presented infoldings of the myelin sheath, irregular myelin lamellation and a great number of Schmidt-Lanterman incisures. In one nerve fasciculus of Case 5 the myelin sheaths of some large myelinated fibres were extremely thickened; the axoplasm exhibited dilated vesicles and disordered microfilaments. These findings were taken as evidence of the occurrence of nerve fibre lesions at the pre-symptomatic stage of the disease, which seem to precede the appearance of amyloid deposition. The lesions affected primarily the Schwann cell and myelin sheath, and spared the unmyelinated fibres.