Delayed hypersensitivity reaction after initial dose of infliximab: a case report.

We report here an unusual case of delayed hypersensitivity reaction in a young woman with ulcerative colitis after the first administration of infliximab (IFX). The patient developed severe serum-sickness-like reaction, and her anti-IFX antibody titer increased rapidly after a single infusion of IFX. The possible reason for the delayed hypersensitivity reaction to a single IFX exposure might be the presensitization of the patient by murine antigens as she had been keeping mice and hamsters as pets for several years.