Progressive nerve lesion in a disease-arrested leprosy patient. An electron microscopic study.

An ulnar nerve biopsy from a patient with purely neural leprosy of the borderline tuberculoid group, who developed ulnar and median paralysis after 2.5 years of DDS therapy, was examined using light and electron microscopes. The nerve parenchyma was largely replaced by collagen fibrils. There were many onion bulbs similar to those seen in hypertrophic neuropathies. Bizarre fibroblasts such as those seen in hereditary sensory neuropathy were also demonstrated. A few Schwann cells contained M. leprae. It is suggested that considerable proliferation of fibrous tissue may be a reactive phenomenon in response to the continued presence of fragmented M. leprae and their products. Ischemia following a marked progressive increase of intraneural collagen is an important cause of atrophy of Schwann cells followed by segmental demyelination and necrosis of the axons in this healed leprosy patient.