Atypical presentations of bullous pemphigoid: Clinical and immunopathological aspects

Bullous pemphigoid may occur in extremely variegated manners, misleading even experienced dermatologists. Indeed the type and/or distribution of lesions may be unusual. Furthermore, there may be an atypical demographic profile of patients, a different clinical course and a different responsiveness to therapy. Up to 20% of the cases the onset is characterized by a non-bullous phase, lasting weeks, months or in particular cases remaining the only manifestation of the disease. During this early phase lesions are generally pruritic erythematous, eczematous or urticarial; however, lesions may also resemble polycyclic, targetoid, nodular or lichenoid lesions. These atypical lesions may also coexist with typical bullae. Other atypical presentations include a vesicular eruption and an erythroderma. Manifestations in children differ from adult forms, presenting an exclusive genital involvement in 50% of cases or a preponderant involvement of the face, the palms and the soles. Rarely bullous pemphigoid is confined to certain body areas, due to particular triggering factors or to a lower disease activity. Therefore, the need to formulate universally recognized diagnostic criteria is increasingly evident, especially for atypical bullous pemphigoid. Direct immunofluorescence of perilesional skin and detection of circulating autoantibodies are mandatory in the diagnosis, especially when the clinical presentation is doubtful.