Spondyloepiphyseal dsplasia tarda (SEDL) is a radiologically distinct, X-chromosome linked primary skeletal dysplasia characterised by disproportionate short-trunked short stature, dysplasia of the large joints (hip) and flattened thoracic and lumber vertebral bodies. Molecular basis for SEDL has been elucidated by the identification of various mutations (currently 430) in the SEDL gene from Xp22 region. The function of the SEDL protein is not known although it is speculated that it may participate in the ER-toGolgi transport as part of a novel highly conserved multiprotein TRAPP complex.

Clinical definition

Spondyloepiphyseal dysplasia tarda (SEDL) is a welldefined, X-linked primary skeletal dysplasia that predominantly affects the spinal vertebral bodies and epiphyses during skeletal growth.1 The condition is not evident at birth, the usual age of presentation being after the first decade of life. Disproportionate (short-trunked) short stature in a male, with or without back pain, is the common presenting feature. Other characteristic clinical features include a broad chest with mild sternal protrusion and limitation of joint motion at the hips and elbows.2 Craniofacial appearance, vision, hearing and intelligence are unaffected in SEDL and there are no consistently associated extraskeletal anomalies. The radiographic manifestations of SEDL are diagnostic, clearly distinguishing it from other conditions that it has most recently been grouped together within the current classification3 (see Table 1). The most characteristic of these is seen in the lateral view of the thoraco-lumbar spine; comprising generalised platyspondyly, narrowing of intervertebral disc spaces, and pathognomonic superior and inferior ‘humps’ involving the posterior two-thirds of the flattened vertebral bodies2 (see Figure 1). These changes are best appreciated in late childhood and adolescence, and may become superimposed by secondary arthritic changes in later decades. The major potential medical complication of the disorder is premature arthritis, predominantly affecting the spine and hip joints.1 Hip joint disease may be severe, necessitating replacement in early adult life.1 There is a wide range of inter- and intrafamilial variability among affected males in regard to severity of disease. Females have also been reported with classic radiographic features of SEDL, 4 but this occurrence is rare, if not unique, and in such females mutations in the SEDL gene are yet to be identified.