MICROSCOPIC MORPHOLOGY OF DIFFERENT TYPES OF URTICARIA

Objective: To identify possible special histopathologic features of di fferent types of urticaria. Design: Hematoxylin-eosin-and toluidine bl ue-stained sections from biopsy specimens of all patients with urticar ia seen from 1990 to 1993. Setting: Inpatient and outpatient services of the Virchow Klinikum, Humboldt University, Berlin, Germany. Partici pants: We studied spontaneous or induced wheals of 108 patients with a cute, chronic, and physical urticaria who consented to an additional b iopsy from uninvolved skin. The controls were 10 normal volunteers wit h wheals that tested positive on a prick test and who had contralatera l normal skin. Main Outcome Measure: Mast cell numbers in both lesiona l and nonlesional skin in the upper and lower dermis of biopsy specime ns from patients and controls. Results: Blind evaluations of microscop ic sections showed dermal edema and dilated lymphatic and vascular (P< .001 for all, Fisher exact test) capillaries almost exclusively in inv olved skin. The same held for inflammatory infiltrates, with significa ntly increased numbers of neutrophils and eosinophils in specimens fro m patients with acute urticaria and those with delayed pressure urtica ria (P<.01 for each). Mast cell numbers were higher in the upper (P<.0 1) and lower dermis (P<.05) of lesional and uninvolved skin of all pat ients with urticaria, with a further increase (P<.01) in patients with disease of more than 10 weeks' duration. Edema and vascular changes w ere most prominent in the skin of patients with cold urticaria (P<.005 ) and mononuclear infiltrates were more pronounced in those with cold urticaria, chronic urticaria, and prick test-positive wheals (P<.05 fo r each) and in the lower dermis of patients with delayed pressure urti caria (P<.001). Conclusions: In all types of urticaria, mechanisms mus t be operative that cause an increase of cutaneous mast cells. Distinc tive pathological features can be identified in different types of urt icaria, although these are not diagnostic.