Klippel-Trenaunay syndrome in a monozygotic male twin: supportive evidence for the concept of paradominant inheritance.

Klippel-Trenaunay-syndrome (KTS) (OMIM 149000) is a congenital slow-flow capillary lymphaticovenous malformation often affecting the lower extremities and accompanied by bone and soft tissue hypertrophy. The cutaneous lesions are always surrounded by regions of unaffected skin in a mosaic pattern. Usually, KTS occurs sporadically but rare reports of familial segregation exist, contributing to the ongoing debate on the issue of heredity in this disease. Herein, we report on identical monozygotic male twins discordant for KTS. This observation strongly supports the model of paradominant inheritance that was recently proposed for this and similar disorders.