Tacrolimus (FK 506)--a new therapeutic agent for severe recalcitrant psoriasis.

BACKGROUND Psoriasis, a disease of unknown etiology, is in some patients severe, extremely debilitating, and unresponsive to conventional therapies, including UV-B, oral psoralen with long-wave UV radiation in the A range (PUVA), oral retinoids, and methotrexate. We report the results from our study of seven patients with refractory psoriasis who were treated with the new immunosuppressive drug, tacrolimus (FK 506). OBSERVATIONS All seven patients showed a dramatic resolution of psoriasis that remained in remission as long as they received full-dose therapy. Serial skin biopsy specimens demonstrated a rapid disappearance of the inflammatory infiltrate and a slower resolution of the epidermal changes. Tacrolimus was well tolerated during the 5.5 to 14 months of observation. Side effects, including nephrotoxicity and hypertension, were controlled by appropriate modification of drug dosage. CONCLUSIONS Tacrolimus, a new immunosuppressive agent, is effective in treating patients with severe recalcitrant psoriasis. The mechanism of its action in psoriasis is unknown, but it may be related to its ability to modulate immune function. Further studies will establish criteria for patient selection and drug dosage, to maximize efficacy of this agent in psoriasis, while minimizing its toxicity.