Co-trimoxazole-induced erythema annulare centrifugum.

Erythema annulare centrifugum (EAC) is an infrequent cutaneous disease characterized by figurate erythematous eruptions that enlarge centrifugally at a rate of 1-3 mm/day with central clearing resulting in an annular or polycyclic appearance. The characteristic skin eruptions of EAC are associated with various underlying systemic disorders, including infections, autoimmune and endocrine diseases, malignancies, and the use of certain drugs like diuretics, non-steroidal antiinflammatory agents, antimalarials, gold, amitriptyline, finasteride, penicillins, and salicylates, though the causal association has not been established. Lesions usually involve the thighs, legs, and buttocks and are characterized histopathologically by dermal perivascular lymphohistiocytic infiltrate. EAC is a benign self-limited disease. A 64-year-old man with pulmonary nocardiosis, on treatment with co-trimoxazole, presented with peripherally spreading raised red-coloured eruptions over thighs, buttocks, and arms. He developed similar lesions in the past, which resolved spontaneously. Cutaneous examination revealed multiple discrete annular erythematous plaques over flexural areas, thighs and buttocks. Skin biopsy showed coat-sleeve peri-appendageal inflammatory infiltrate in the dermis. Pulmonary nocardiosis was confirmed by positive cultures from broncho-alveolar lavage and PCR. A diagnosis of erythema annulare centrifugum, deep type, possibly associated with nocardiosis and/or co-trimoxazole, was made. The lesions subsided after stopping co-trimoxazole. [ABSTRACT FROM AUTHOR]