The diagnostic significance of immunoglobulin and fibrin deposition in lichen planus.

Direct immunofluorescent (IF) staining was performed on biopsy specimens from fifty-three patients with active lichen planus. In fifteen of these cases uninvolved skin sites were also examined. Globular or cytoid body-like deposits of immunoglobulins, mainly IgM, were detected in forty-six of the active lesions, and in half the uninvolved skin biopsies. The deposition of fibrin in the papillary dermis and around follicular structures was seen only in the active lichen planus papules. The significance of these findings was assessed by comparison with the IF results obtained in 252 biopsies from various cutaneous disorders, stained by the same technique during the period of this study. Although the presence of immunoglobulin cytoid bodies and fibrin was found to be highly characteristic of lichen planus, these findings were not specifically diagnostic. Morphologically identical deposits were seen not infrequently in lupus erythematosus and in eczema. Active lesions of dermatitis herpetiformis, erythema multiforme and other rare dermatoses also showed these cytoid body-like immunoglobulin deposits.