Unilateral non-pigmenting fixed drug eruption associated with cotrimoxazole.

The pathogenesis of fixed drug eruption (FDE) is still unknown. One of the most common associations of FDE is the use of sulfonamides. Cotrimoxazole (trimethoprim with sulfamethoxazole) is one of the most commonly prescribed sulfonamide drugs. Non-pigmenting FDE (NPFDE) is a a relatively rare condition and only a few cases have been reported. We describe a case of unilateral NPFDE in a 45-year-old man whose lesions were on his right leg and foot as well as his ipsilateral penile skin. Cotrimoxazole was suspected as the offending drug and its role was confirmed by an oral challenge test.