Myelinated and unmyelinated fibers in sural nerve biopsy of a case with lepromatous leprosy--a quantitative approach.

A 64-year-old Cambodian male with lepromatous leprosy of several months' duration, with only brief previous treatment, had symmetrical patchy loss of pain and thermal sensibility including the lateral foot regions. Quantitative assessment by light and electron microscopy revealed normal counts of myelinated fibers (MF) and an increased number of unmyelinated fibers (UF). The respective abnormal histograms and the qualitative differentiation of UF-associated Schwann cells suggested a combination of segmental demyelination with Wallerian degeneration of MF, and a loss of genuine UF, concomitant with considerable regenerative activity of both fiber populations.