Histopathologic and direct immunofluorescence findings of the papulopustular lesions in Behçet's disease.

Although papulopustular lesions are common in patients with Behçet's disease (BD), clinically they may not be differentiated from other diseases with papulopustular presentation such as acne vulgaris or folliculitis. Therefore, there is disagreement as to whether they should be used as a diagnostic criterion in BD. The aim of this study was to determine whether the histopathologic evaluation of the papulopustular lesions may assist in the diagnosis of BD. Eighteen patients with BD and 16 control patients consisting of eleven patients with bacterial folliculitis and five patients with acne vulgaris were included in the study. After the detailed histopathologic evaluation by two pathologists who were blinded to the clinical diagnoses, the histopathologic findings were classified into three patterns as follows; pattern I: vasculitis (lymphocytic or leucocytoclastic); pattern II: folliculitis and/or perifolliculitis; pattern III: superficial and/or deep perivascular, and/or interstitial dermatitis. In addition, direct immunofluorescence studies were performed in order to evaluate the deposition of IgM, IgG, IgA, C3, or fibrinogen in dermal blood vessels. 27.8% of the patients with BD (5 patients) revealed lymphocytic vasculitis, while none of the control group did; and the difference was found statistically significant (P=0.046). The rate of pattern II which included folliculitis and/or perifolliculitis was 50.0% in control patients and 16.7% in the patients with BD; and the difference was found statistically significant (P=0.038). No difference was found between the two groups with regard to pattern III or direct immunofluorescence findings (P>0.05). Our results indicate that only vasculitic changes can be useful when histopathological features of papulopustular lesions are to be employed as a diagnostic criterion in patients with suspected BD.