Monozygotic twins discordant for spondylocostal dysostosis

Spondylocostal dysostosis (SCD) is a rare skeletal dysplasia with clinical and radiological manifestations, consisting of short neck and trunk, barrel-shaped chest, protuberant abdomen, scoliosis and abnormalities of vertebral segmentation and of the ribs. Both autosomal recessive and autosomal dominant inheritance have been described. We report on monozygotic twins discordant for the syndrome, either due to a post-zygotic mutation or development of a phenocopy. To our best knowledge, this is the fourth report of SCD in identical twins, and the first one of discordance in monozygotic twins.