515 Hyperkeratotic bullous pemphigoid: 5 cases of a new clinical subset

Abstract

The clinical features of bullous pemphigoid are polymorphous. Several atypical forms of bullous pemphigoid have been described and the diagnosis of bullous pemphigoid critically relies on immunopathologic findings. We reported 5 cases of a new subtype of atypical bullous pemphigoid, which we named hyperkeratotic bullous pemphigoid. The age of the patients ranged between 30 and 77 years. All 5 patients complained of a pruritic eruption with diffuse hyperkeratotic cutaneous lesions, in some cases associated to blisters on normal or erythematous skin. They showed also a thick palmo-plantar hyperkeratosis. All patients showed deposition of IgG and/or complement along the basement membrane zone by direct immunofluorescence and 2 of 5 IgG staining of epidermal side of salt-split skin by indirect immunofluorescence. In 3 patients peripheric hyper-eosinophilia was detected. In addition, in 4 out of 5 patients, extreme high IgE levels was present, but IgE anti-BP180 was negative and high level of anti-BP230 IgE was highlighted only in 2 patients. IgG anti-BP180 was positive in four patients, while IgG anti-BP230 was found exclusively in one patient. Several blistering disorders caused by mutations in adhesion molecules may show alteration of the keratinization process. We speculate that in our atypical bullous pemphigoid patients circulating autoantibodies against hemi-desmosomal proteins could disrupt dermal-epidermal adhesion, leading not only to blister formation, but also to abnormal keratinization. However, to state the association between this clinical phenotype and immunopathologic findings further studies are needed. In conclusion, we reported a new subset of atypical bullous pemphigoid, that should be taken into account in patients with pruritus and hyperkeratotic palms and soles. Pathologic and immunopathologic investigations are mandatory to differentiate hyperkeratotic bullous pemphigoid from several diseases, including pityriasis rubra pilaris and inherited palmo-plantar hyperkeratosis.