Focal adhesion kinase is expressed in acantholytic keratinocytes associated with pemphigus vulgaris and pemphigus foliaceus.

Focal adhesion kinase is a protein-tyrosine kinase that is found in cellular contact sites and is phosphorylated in response to cell attachment. It is possible that the immunohistochemical detection of this enzyme might be increased in keratinocytes involved in an acantholytic process. Normal skin, pemphigus vulgaris and foliaceus, Darier's disease, Hailey--Hailey disease, warty dyskeratoma, Grover's disease and spongiotic dermatitis were assayed for the immunohistochemical expression of focal adhesion kinase. Focal adhesion kinase was not observed in normal epidermis. This antigen was observed in keratinocytes adjacent to acantholytic spaces and in acantholytic cells in pemphigus vulgaris and foliaceus. Focal adhesion kinase was not detected in keratinocytes involved in focal acantholytic dyskeratoses such as Darier's disease, Grover's disease and warty dyskeratoma but was weakly detected in Hailey--Hailey disease. One consequence of immunologically mediated acantholysis is the upregulation of focal adhesion kinase possibly as a component of biochemical pathways that reconstruct the process of adhesion or respond to the process of acantholysis.