Concordance for Gender Dysphoria in Genetic Female Monozygotic (Identical) Triplets

Male-to-female and female-to-male transsexual siblings with pedophilic father: A case report

Key Clinical Message

The reported case was the fourth instance of MF-FM transsexual non-twin siblings, and their father had pedophilia. Further studies are needed to evaluate whether there is a genetic link between gender dysphoria (GD) and pedophilic disorder.

Abstract

Gender dysphoria (GD) refers to a persistent incongruence between a person's experienced gender and assigned gender, causing discomfort or distress. Family studies and reports of GD co-occurrence in a family can help clarify whether GD is a familial phenomenon. In this case report, a male-to-female (MTF) and female-to-male (FTM) transsexual sibling pair with a father with pedophilia was presented, which is a rare occurrence. More research is necessary to understand the potential genetic connection between GD and pedophilia.

Sexual Orientation in Twins: Evidence That Human Sexual Identity May Be Determined Five Days Following Fertilization

Human same-sex sexual attraction has been recorded from the beginning of written history. It remains a controversial topic, but recent theories favor prenatal influences. A paradox is the occurrence of same-sex orientation in twins in that there is a higher level of concordance in monozygous twins compared to that in dizygous twins or non-twin siblings. If sexual orientation was entirely genetically determined monozygous twins would be expected to have identical sexual inclinations. Monozygous twins have twice the incidence of sexual concordance in comparison to dizygous twins but a third of these pairs have different sexual identities. An explanation for this disparity may lie in the time an embryo splits to form two separate fetuses. If splitting occurs early in twin development each twin may develop his or her own sexual identity; splitting occurring later results in twins that have the same sexual dispositions. A possible process for such determination may be in the mitochondria, with universal maternal inheritance of a proportion of normal functioning but alternate mitochondria. Variation in the distribution of these mitochondria in neural precursor cells becomes a mechanism for the development of intrinsic sexual orientation and for the spectrum of human sexual inclinations. The timing of embryonic splitting may be determined from the examination of fetal membranes, and the concept of early fetal sexual orientation is open to support or disproval.