[Secondary sulfone resistance--presentation of a case of leprosy-Oswaldo Cruz Foundation, Rio de Janeiro-Brazil].

Report on a case of dapsone resistance in a BL patient with clinical diagnosis and laboratory confirmation. The resistance appeared after 17 years of dapsone treatment, and the laboratory tests revealed total resistance to all the tested dapsone concentrations. The case reported occurred in the city of Rio de Janeiro (Brazil) which presents a leprosy prevalence of 1.79/1,000.