Cutaneous leukocytoclastic vasculitis: the yield of direct immunofluorescence study.

BACKGROUND Leukocytoclastic vasculitis (LCV) is a clinico-pathological entity. Previous direct immunofluorescence study (DIF) studies of vasculitis showed positive findings mainly in the early stage of the disease. OBJECTIVE To study the positive yield and patterns of DIF in patients with various stages of LCV. DESIGN One hundred patients with LCV who attended the Department of Dermatology, Siriraj Hospital from 1997 to 2000 were enrolled in the study. RESULTS The study showed immunoreactive deposits in blood vessel walls in 76 cases (76%). Forty seven per cent of patients showed immunoreactant deposit only in superficial blood vessel walls, 3% had deposits only in deep blood vessel walls. Superficial and deep blood vessel wall deposits were seen in 26%. Dermo-epidermal deposit in addition to blood vessel wall deposit was found in 39%. The most common immunoreactive deposit was C3 (71%), followed by IgM (35%), IgA (12%) and IgG (8%) respectively. The age of the skin lesions at the time of biopsy ranged from 1 to 7 days. 82% of patients with one day old lesions showed immunoreactive deposits in the blood vessel walls and 74% of the group with lesions aged 2-7 days at the time of biopsy showed immunoreactive deposits in the blood vessel walls. CONCLUSION The present study showed a 76% positive yield for DIF study in patients with LCV when biopsies were performed within one week of onset. There was a tendency for the percentage of positive DIF results to decline when the biopsy was performed on lesions that were more than 1 day old.