Monozygotic female twins discordant for phenotype of Wilson's disease

Wilson's disease (WD) is an autosomal recessive disorder characterized by the functional disruption of the copper-transporting protein adenosine triphosphatase 7B (ATP-ase 7B). The disease is caused by mutations in ATP7B gene. It seems that the type of mutation in ATP7B only to some degree determines phenotypic manifestation of WD. We examined two pairs of monozygotic twins discordant for WD phenotype. The first set of twins were ATP7B compound heterozygotes c.3207C>A (p.H1069Q)/c.1211_1212insA (p.N404Kfs). The index case developed severe liver failure followed by depressive symptoms, dysarthria, and tremor at the age of 36. Her sister remained presymptomatic at diagnosis at the age of 39. The second twins were ATP7B c.3207C.A (p.H1069Q) homozygotes. The index case presented with dysarthria and tremor at the age of 26. Her sister remained clinically presymptomatic at diagnosis at the age of 28. We concluded that the phenotypic characteristics of WD are possibly attributable to epigenetic/environmental factors.