Erythema nodosum, lichen planus and lichen nitidus in Crohn's disease: report of a case and analysis of T cell receptor V gene expression in the cutaneous and intestinal lesions.

A wide variety of cutaneous manifestations have been described in association with Crohn's disease (CD). We describe a patient with a 2-year history of CD who developed both lichen planus (LP) and lichen nitidus (LN) in addition to erythema nodosum (EN) lesions. The clinical course of EN reflected the activity of the bowel disease, whereas LP and LN appeared to persist independently of the ongoing disease activity. Immunohistochemical studies of the infiltrates in these cutaneous and intestinal lesions showed that the majority of the infiltrates were T cells expressing T cell receptor (TCR)-alpha beta. Analyses of TCR V gene expression in these infiltrating T cells demonstrated a different pattern of V beta expression that provides an explanation for the difference in the clinical courses of these lesions. LP and LN lesions are likely to be mediated by T cells with antigen specificity distinct from those that cause EN and intestinal lesions.