A case of relapse with drug-susceptible M. leprae after multidrug therapy.

A male born in 1930 was diagnosed as smear-positive borderline leprosy in 1971, and was treated with dapsone and/or sulfamethoxypyridazine from 1972 to 1980 with clinical improvement. However, new skin lesions with smears strongly positive appeared in August 1980, and he was diagnosed as having downgraded to lepromatous (LL) leprosy, but the bacilli recovered from the skin biopsy were fully susceptible to both dapsone and rifampin by mouse foot pad technique. Between 1981 and 1983, the patient was treated with 24 months of rifampin 600 mg and dapsone 100 mg daily, supplemented with prothionamide 500 mg daily during the initial 3 months, and his skin lesions gradually improved during treatment with the combined regimen.