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Larsen syndrome, autosomal recessive and spondyloepiphyseal dysplasia with congenital joint dislocations (includes humerospinal dysostosis, spondyloepiphyseal dysplasia, Omani type and chondrodysplasia with multiple dislocations). Larsen syndrome, autosomal recessive (MIM 245600) and spondyloepiphyseal dysplasia with congenital joint dislocations (MIM 143095) which includes humerospinal dysostosis (HSD), spondyloepiphyseal dysplasia, Omani type and chondrodysplasia with multiple joint dislocations are allelic disorders with similar clinical findings. All are caused by mutations in the carbohydrate sulfotransferase 3 gene (CHST3). It has been suggested that they may represent a single disorder with various age dependent manifestations. Alternatively, different loss of function mutations with various severities may cause a clinical spectrum. When patients are evaluated in the neonatal period or as young children, they are often diagnosed with Larsen syndrome, humerospinal dysostosis or chondrodysplasia with multiple dislocations. Patients with Larsen syndrome or humerospinal dysostosis typically have a birth length below the 3rd percentile. Growth often remains below the 3rd percentile throughout childhood and adults typically have short stature. The characteristic feature of patients with CHST3 mutations are congenital dislocations. Almost all patients have congenital knee dislocations and clubfoot. Dislocations or contractures of the elbows and hips are also common. Patients evaluated during childhood typically have features of spondyloepiphyseal dysplasia, Omani type. Older patients have severe degeneration of the intervertebral discs with thoracic kyphoscoliosis. Posterior and inferior scalloping or coronal clefting of lumbar vertebrae and widening of the interpedicular distance from T12 to L1 or L2 are evident on X-ray. Fusion of vertebral bodies eventually occurs. Several patients with CHST3 mutations have also been described with abnormalities of the heart valves. Older patients may present with dislocations that have improved either spontaneously or following surgical intervention. Arthritis of the hips and spine, intervertebral disc degeneration with trunk shortening and rigid kyphoscoliosis also dominates the clinical picture. Patients with CHST3 mutations must be differentiated from patients with classic autosomal dominant Larsen syndrome and Desbuquois dysplasia. Autosomal dominant Larsen syndrome is caused by mutations in the FLNB gene. Those with CHST3 mutations can be differentiated by the lack of facial flattening and the lack of advanced carpal age. In addition, patients with classic Larsen syndrome do not have the vertebral changes seen in patients with CHST3 mutations. Desbuquois dysplasia is an autosomal recessive chondrodysplasia caused by mutations in the CANT1 gene. Individuals with Desbuquois dysplasia have vertebral clefting, facial flattening and advanced carpal age which differentiates these patients from individuals with CHST3 mutations.