Crohn ' s disease in monozygotic twins

Seventeen pairs of identical twins concordant for Crohn's disease have been recorded (Table I). We describe a further set of affected twins unusual in that the disease developed simultaneously and at the same site in each patient at a time when they had been living in different environments for 6 years. As in a minority of previous reports (Crismer et al., 1963; Goldstein et al., 1976; Morichau-Beauchant et al., 1977; Klein et al., 1980; Gonzalez et al., 1983), monozygosity in our patients was investigated by histocompatibility typing and blood group analysis.