Background and design: We have observed that tissue-fixed deposits of immunoglobulin (Ig) are occasionally present in the cytoplasm (CYT) of epidermal keratinocytes. This study was conducted to examine the frequency, significance, and possible cause of this finding.
Results: Direct immunofluorescence studies were performed on 302 sequential skin specimens obtained from patients with lupus erythematosus (n = 98), bullous diseases (n = 114), or other dermatoses (n = 90). Abnormal epidermal CYT deposits were observed in 22 of the patients with lupus erythematosus (22.5%), four of those with bullous diseases (3.5%), and two of those with other dermatoses (2.2%). The deposits were more common in systemic than in discoid lupus erythematosus, and in skin lesions than in normal skin. By indirect immunofluorescence, circulating antibodies to epidermal upper CYT antigens were present in 100% of 12 patients with tissue-fixed CYT deposits (average antibody titer, 300) and in 21% of 19 individuals without CYT deposits (average titer, 43). By Western immunoblot analysis these antibodies were directed to proteins in keratin extracts of skin.
Conclusions: These findings indicate that deposits of Ig in the cytoplasm of keratinocytes in human skin are associated with high levels of serum antibodies to upper CYT antigens and with lupus erythematosus.