B3GAT3, encoding beta-1,3-glucuronyltransferase 3, has an important role in proteoglycan biosynthesis. Homozygous B3GAT3 mutations have been associated with short stature, skeletal deformities, and congenital heart defects. There is a novel B3GAT3-related disorder with craniosynostosis and bone fragility, due to a unique homozygous mutation in B3GAT3.