[Chromomycosis of the buttocks]. 
We report a case of chromomycosis involving buttocks in a 63 years old white male patient, who was living temporaly in several tropical areas of Argentine, due to professional reasons.  The lesion had arisen 28 years ago, located in his right buttock.  Clinical examination showed a large, erythematous and violaceus plaque, with atrophic center and peripheric warty nodules.  Diagnosis was established on histologic and mycologic examination.  Fonsecaea pedrosoi was isolated as the ethiologic agent.  Treatment was instituted with oral 5-fluorocytosine and topic 5-fluorouracil with good evolution.  We found our case interesting for several reasons: A) Chromomycosis is an unfrequent disease in Argentine.  B) Buttock involvement is unusual.  C) Clinically the patient simulated lupus vulgaris; this situation was a cause of delayed correct diagnosis and treatment.