Leukocytoclastic vasculitis induced by low-dose methotrexate: in vitro evidence for an immunologic mechanism

The rare occurrence of methotrexate (MTX)-induced vasculitis has been associated mainly with high or intermediate MTX doses. We report herein a case of cutaneous leukocytoclastic vasculitis (LCV) following treatment with low-dose oral MTX (7.5 mg/week) for rheumatoid arthritis. The histological findings of a cutaneous lesion were consistent with drug-induced vasculitis. The clinical and histological findings, including the temporal relationship between MTX intake and the onset of vasculitis, and the results of withdrawal and rechallenge tests, suggest a causal relationship, and indicate a drug-induced LCV due to MTX. The role of MTX in the induction of the vasculitis was further supported by a positive mast cell degranulation (MCD) test.