A study of keratin expression in benign familial chronic pemphigus.

We studied keratin expression in the involved and uninvolved skin of six benign familial chronic pemphigus (BFCP) patients, using monoclonal antibodies specific for various keratin polypeptides and immunohistopathologic techniques. Normal and psoriatic (i.e., hyperproliferative) skin specimens served as controls. The uninvolved BFCP epidermis showed keratin profiles identical to that of normal epidermis. In the acantholytic epidermal segments of the involved BFCP skin, some of the lower suprabasal acantholytic cells failed to express keratin polypeptides 10 and 11 (Moll's catalog). This delay in expression of suprabasal keratins was not accompanied by an expression of hyperproliferative keratin polypeptide 16. Also, some of the lower suprabasal acantholytic cells of the involved BFCP epidermis retained staining by the antikeratin KS-1A3 antibody, which in the normal, psoriatic, and uninvolved epidermis was limited to the basal cell layer. Staining for keratin polypeptide 18 was negative in the epidermis of all four types of specimens. We believe that the delay in suprabasal keratin expression in the involved BFCP epidermis was more likely secondary to the acantholysis (i.e., "arrest of differentiation" due to acantholysis) rather than due to a primary defect in keratin expression.