Cutaneous mastocytosis without clinically obvious skin lesions.

A patient with cutaneous mastocytosis had intractable pruritus but no visible skin lesions. Skin biopsies and urinary histamine and prostaglandin D2 metabolite assays confirmed the diagnosis. Adding therapy with psoralens and ultraviolet A to the antihistamine regimen markedly decreased the patient's pruritus. In patients with pruritus, flushing, syncope, or other symptoms associated with mastocytosis, this diagnosis should be considered even in the absence of specific skin lesions.