Histological criteria of bullous pemphigoid. Correlation with immunoblot analysis

The aim of this study was to evaluate the histological findings observed in patients with bullous pemphigoid in whom the diagnosis of bullous pemphigo id could be confirmed by direct immunofluoresence and immunoblot serum anal ysis. Seven histological criteria were considered for selection of skin bio psy specimens :1) cleavage of dermal epidermal junction :2) migration of eo sinophils along dermal epidermal junction :3) presence of intra epidermal e osinophils (with or without associated spongiosis) ;4) absence of keratinoc yte necrosis :5) absence of acantholysis :6) absence of dermal fibrosis :7) absence of vasculitis. Depending on the number of criteria observed the hi stological picture was considered as : highly suggestive or poorly suggesti ve of bullous pemphigoid. The histological picture was considered as highly suggestive in 50 % of cases, suggestive or poorly suggestive in 37 % and 1 3 % of cases respectively. Migration of eosinophils along dermal epidermal junction was observed in 23 biopsy specimens (50 %). Histological findings considered as poorly suggestive of bullons pemphigoid consisted of a prurig o-like or an eczematous-like or a drug induced-like picture or no specific cutaneous erosions. An histological picture highly suggestive of bullons pe mphigoid was observed in 67 % of patients whose serum contained anti-BPAG2 antibodies and in only 36 % patients of without anti-BPAG2 antibodies (p = 0.04). On the contrary, only one bullous pemphigoid patient (4 %) with circ ulating anti-BPAG2 antibodies had a histological picture poorly suggestive of bullous pemphigoid. These findings are in accordance with the pathogenic properties of anti-BPAG2 antibodies demonstrated in animal models. This st udy showed that :1) typical histological findings of ballous pemphigoid are only observed in 50 % of skin biopsy specimens. 2) The diagnosis of bullou s pemphigoid should be considered in elderly patients even when a poorly sp ecific prurigo-like or eczematous-like histological picture is observed. Mo reover, it underlines the usefulness of direct immunofluoresence of skin bi opsy specimens and indirect immunoflouresence and immunoblot analysis of se rum in such atypical cases of bullons pemphigoid.