Psoriasis associated with idiopathic CD 4+ T ‐cell lymphopenia: a regulatory T ‐cell defect?

Summary Idiopathic CD 4 + lymphocytopenia ( ICL ) is a rare immunodeficiency syndrome of unknown origin for which the increased risks of opportunistic infections and of malignancies have been well established; however, skin dysimmune diseases, including psoriasis, have been scarcely reported up to now. We report herein the severe course of psoriasis in four patients with ICL , and show evidence for a defect in the skin recruitment of regulatory CD 4 + F ox P 3 + T cells. These data raise the apparent paradigm of the occurrence of a severe immunomediated disease together with a profound T ‐cell defect, a model that might also apply to other immune deficiencies associated with psoriasis.