Type 1 waardenburg syndrome in monozygotic twins and their family

Abstract

Waardenburg Syndrome is a rare genetic disorder with an incidence of 1 in 40.000 individuals. It is caused by mutations in multiple genes such as PAX3, MITF, SNAI2 and SOX10. These genetic alterations cause abnormal development of tissues derived from neural crest cells and produce phenotypic characteristic findings as light blue iris or iris heterochromia, poliosis and sensorineural hearing loss, among others. The aim of this article is to report to the literature a rare case of monozygotic twins with typical clinical findings of type 1 Waardenburg Syndrome with different phenotype between them, including their mother and grandmother. The use of W index to identify cantorum dystopia and to classify the cases according to the four types of Waardenburg syndrome is explained. The findings reported here show the variability of phenotypic manifestations of type 1 Waardenburg Syndrome within a family and particularly in monozygotic twins, which is explained by the variable expression of specific genes or the interaction of these with modifier genes. Given the fetal exposure of the twins to alcohol, it is proposed that the variable expression of Waardenburg Syndrome would be influenced by exposure to environmental agents.