Postcoital fixed drug eruption in a man sensitive to trimethoprim-sulphamethoxazole

We describe a 34-year-old patient with a probable fixed drug eruption caused by trimethoprim-sulphamethoxazole, having developed the eruption after sexual intercourse with his wife, who was taking the drug. The patient was known to be allergic to trimethoprim-sulphamethoxazole by history, and the lesion then recurred at the same site when the drug was administered orally to his wife. To the best of our knowledge, this is the first report describing postcoital fixed drug eruption. Physicians should thus be aware of unusual and atypical forms of fixed drug eruption. Fixed drug eruption (FDE) is an unusual form of adverse drug reaction, in which one or more lesions appear in precisely the same place or places each time the precipitating drug is administered. The entity was first described by Bourns in 1889, but Brocq then coined the name some years later. FDE may occur anywhere on the skin or mucous membranes, but more frequently occurs on the genitalia and lips. Lesions are usually sharply demarcated patches which quickly become urticarial and sometimes vesicular in the centre. Itching or burning may also be present. Lesions generally leave prolonged postinflammatory hyperpigmentation. The exact pathogenesis of FDE has not been determined, but recent reports have underlined the importance of T lymphocytes, mast cells, keratinocytes and cytokines in the origin of the lesions. We now report a case of FDE apparently caused by trimethoprim-sulphamethoxazole in a male after intercourse with his wife, who was taking the drug. Such FDE, caused by contact with a drug seemingly present in the vaginal fluid, has not been previously described in the literature as far as we know.