Treatment of chronic erythema nodosum leprosum with cyclosporine A produces clinical and immunohistologic remission.

We have treated three leprosy patients suffering from chronic, steroid-dependent erythema nodosum leprosum (ENL) with cyclosporine A (CsA). Excellent results were obtained in two patients. Extra-cutaneous manifestations of the reactional state were completely suppressed, and the development of new skin lesions was sharply curtailed. Immunohistologic abnormalities characteristic of active ENL were corrected. Lymphocyte subpopulations and anti-mycobacterial antibody levels in peripheral blood were unaffected. The third patient showed only a partial response to CsA, but satisfactory blood levels were never obtained in this individual because of dose-related gastrointestinal toxicity. The effectiveness of CsA in the treatment of ENL is consistent with the hypothesis that aberrant activation of a subset of T-helper cells is involved in the pathogenesis of this reaction. CsA may have a role in the treatment of chronic ENL that has failed to respond to conventional therapeutic modalities.