Fixed drug eruption with interferon-beta-1b.

A 32-year-old woman with multiple sclerosis who developed non-injection-site-related fixed drug eruption with interferon-beta-1b. Erythematous plaques started appearing 1 month after the drug was introduced, and increased in number following each administration. The histopathology of a skin biopsy was consistent with fixed drug eruption. The drug was subsequently ceased, with resolution of the rash 6 weeks later.