Gender identity disorder and anorexia nervosa in male monozygotic twins

Objective: Male identical twins with gender identity disorder (GID) in childhood and anorexia nervosa (AN) are presented. Etiologic aspects and the relationship among gender identity, sexual orientation, body dissatisfaction, and AN are discussed. Method: Case reports and a review of the literature are reported. Results: In childhood, both twins showed an atypical gender behavior. Whereas one of the twins later developed a transsexual gender identity and asked for sex reassignment, the other developed a male identity but his appearance and clothing are effeminate. According to their biologic sex, they are concordant in regard to their homosexual orientation. In adolescence, both developed AN. Monozygotism was proved by DNA analysis. Discussion: GID in childhood could be at least partly hereditary, whereas the development of the later phenotype of the gender identification is more determined by environmental factors. GID might be a risk factor for the development of AN. (C) 2004 by Wiley Periodicals, Inc.