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Spondyloepiphyseal dysplasia tarda (SEDT) is characterized by disproportionate short stature in adolescence or adulthood, associated with a short trunk and arms and barrel-shaped chest. The X-linked variant of the disease is most common, with an estimated prevalence of 1 in 150,000-200,000. Patients may have normal body proportions at birth. The condition typically manifests around puberty with a short neck, scoliosis or thoracic kyphosis, lumbar hyperlordosis, and early-onset progressive osteoarthritis of the hips and knees. Many patients achieve an adult height of more than 153 cm and true dwarfism may not be present. Radiographic findings appear prior to puberty and may include multiple epiphyseal abnormalities, flattened vertebral bodies, narrow disc spaces, hypoplastic odontoid process, short femoral neck, and coxa vara. SEDT may be transmitted as an X-linked recessive, autosomal recessive or autosomal dominant trait. The X-linked recessive type is caused by mutations in the TRAPPC2 gene (locus Xp22.2-p22.1). |