[Drug exanthema in connection with trimethoprim and sulfamethoxazole treatment, triggered by leech therapy].

In a 58-year-old hospitalized woman with gonarthrosis a leech therapy was applied to both knee joints. In the evening of the following day she observed strong pruritus in the area of the leech bites; in addition a maculopapular exanthema appeared on the torso and her lower extremities. The allergic reaction lasted four days. Administration of antihistamines only led to a slight improvement of the symptoms. A full restitution could only be achieved after a systemic dose of glucocorticoids on the fourth day after leech therapy. Eight days before beginning of the leech therapy a five-day antibiotic therapy with trimethoprim and sulfamethoxazole (Cotrim forte) had been administered to treat an uncomplicated urinary infection. Allergic reactions are well-known complications of these antibiotics and of leech therapy. The four-day duration of the allergic reaction after leech therapy, however, was untypical. In order to explain these symptoms, a prick test and an epicutaneous test for the antibiotic components were executed five weeks after the leech therapy. Furthermore, a second leech therapy was administered and a lymphocyte transformation test (LTT) was carried out. The results of the LTT showed a sensitization for sulfamethoxazole and a possible sensitization for trimethoprim, the results of the epicutaneous test showed a positive reaction to sodium lauryl sulfate, a component of the antibiotic. In the area of the leech bites a clear local skin reaction was observed. These results suggest a drug exanthema, in all probability triggered by the leech therapy.