Peripheral neuropathy in late-onset Krabbe's disease: histochemical and ultrastructural findings.

We performed histochemical and ultrastructural studies on a sural nerve biopsy specimen obtained from a 31-year-old man with late-onset Krabbe's disease. Myelin sheaths were uniformly thin for the fiber diameter, with a moderate reduction in the myelinated fiber population. Despite a few small onion-bulb formations, quantitative studies demonstrated uniformly thin myelin sheaths and less variability in internodal lengths. This suggests that the main pathophysiology of the peripheral neuropathy observed in late-onset Krabbe's disease is hypomyelination rather than segmental demyelination as in infantile Krabbe's disease. Ultrastructurally, curvilinear lamellar cytoplasmic inclusions were observed in Schwann cells and fibroblasts.