[Evaluation of histological criteria for bullous pemphigoid. Correlation with antigens recognized by immunoblotting of anti-epidermal autoantibodies].

The aim of this study was to evaluate the histological findings observed in patients with bullous pemphigoid in whom the diagnosis of bullous pemphigoid could be confirmed by direct immunofluorescence and immunoblot serum analysis. Seven histological criteria were considered for selection of skin biopsy specimens: 1) cleavage of dermal epidermal junction; 2) migration of eosinophils along dermal epidermal junction; 3) presence of intra epidermal eosinophils (with or without associated spongiosis); 4) absence of keratinocyte necrosis; 5) absence of acantholysis; 6) absence of dermal fibrosis; 7) absence of vasculitis. Depending on the number of criteria observed the histological picture was considered as: highly suggestive, suggestive or poorly suggestive of bullous pemphigoid. The histological picture was considered as highly suggestive in 50% of cases, suggestive or poorly suggestive in 37% and 13% of cases respectively. Migration of eosinophils along dermal epidermal junction was observed in 23 biopsy specimens (50%). Histological findings considered as poorly suggestive of bullous pemphigoid consisted of a prurigo-like or an eczematous-like or a drug induced-like picture or no specific cutaneous erosions. An histological picture highly suggestive of bullous pemphigoid 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 circulating 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 study showed that: 1) typical histological findings of bullous pemphigoid are only observed in 50% of skin biopsy specimens. 2) The diagnosis of bullous pemphigoid should be considered in elderly patients even when a poorly specific prurigo-like or eczematous-like histological picture is observed. Moreover, it underlines the usefulness of direct immunofluorescence of skin biopsy specimens and indirect immunofluorescence and immunoblot analysis of serum in such atypical cases of bullous pemphigoid.