Famciclovir-induced leukocytoclastic vasculitis

To report a case of famciclovir-induced leukocytoclastic vasculitis (LCV).

A 67-year-old white female presented to the hospital for evaluation of large, bilateral palpable purpura; coalescing ulcers with central eschars; and small, red violaceous papules on her legs and groin. Approximately 2 months prior to this hospitalization, the woman was diagnosed with shingles of her left T1-T2 nerve distribution and was treated with famciclovir 500 mg 3 times daily, which was her first exposure to this medication. Her shingles resolved; however, on day 4 of treatment, she began to notice red spots on both of her legs that began to progressively blister and increase in size. She discontinued famciclovir at that time. The rash persisted and spread to her abdomen, groin, legs, feet, and toes. She underwent punch biopsy that revealed LCV. Workup was negative for antinuclear antibody, rheumatoid factor, hepatitis B and C virus, perinuclear-staining antineutrophil cytoplasmic antibodies, cytoplasmic-staining antineutrophil cytoplasmic antibodies, antibodies to extractable nuclear antigens, proteinase 3, and myeloperoxidase. The patient improved with daily oral steroids and local wound care.

LCV has been reported only once before in the English literature as of January 2008. The most common cause of LCV is medication use, but it is a diagnosis of exclusion. It is hypothesized that drugs act as haptens, which cause an immune response. An objective causality assessment using the Naranjo probability scale suggested that famciclovir was the probable cause of LCV in this patient.

Healthcare professionals should be aware of the possible development of famciclovir-induced LCV.