Carbohydrate sulfotransferase 3 (CHST3) is an enzyme with chondroitin 6-sulfotransferase activity. It is crucial for the sulfation of chondroitin-containing proteoglycans, such as aggrecan, the main proteoglycan in cartilage. Deficiency of CHST3 was first found in a large inbred kindred from Oman segregating a skeletal phenotype described as spondylo-epiphyseal dysplasia [Rajab et al., 2004; Thiele et al., 2004]. In 2008, we identifiedCHST3mutations in six unrelated patients who had presented with joint dislocations at birth and had received the diagnosis of recessive Larsen syndrome or humero-spinal dysostosis (HSD)[Hermanns et al., 2008]. We have since identified CHST3 mutations in 17 additional families and report here on the series of 24 subjects with Spondyloepiphyseal dysplasia (SED) with joint luxations, CHST3 type.