Dapsone neuropathy--report of three cases and pathologic features of a motor nerve.

We report the clinical features, electrophysiologic findings, and dapsone and isoniazid excretion studies in three young people who ingested excessive amounts (2-4 times the prescribed dose) of dapsone for hypopigmented macules and who developed, subacutely, progressive motor neuropathy a few months later. Pathologic studies on a biopsied motor nerve confirmed the electrophysiologic conclusion of distal motor axonopathy. All made a rapid recovery in a few months after dapsone was stopped, although electrical abnormalities persisted. One patient was a rapid acetylator of isoniazid.