Spondyloepiphyseal dysplasia congenita (SEDC)

SEDc: associated with a mutation in the collagen II gene (COL2A1) and is transmitted in an autosomal dominant manner. SEDT: Inheritance can be X-linked recessive, autosomal recessive, or autosomal dominant. The X-linked form, which is the most common, is caused by mutations in the TRAPPC2 gene (locus Xp22.2-p22.1).

The most common form is congenital (SEDc) with autosomal dominant inheritance, which is characterized by disharmonious short stature (short trunk compared to limbs with pectus carinatum), epiphyseal and vertebral anomalies (platyspondema). Skeletal abnormalities appear at birth and develop over time. Bone growth is slowed down, especially in the epiphyses of long bones (primarily the femoral head) and in the pelvis. Affected individuals have some specific phenotypic features: a short neck, a pelvis that is located further back than the shoulders, and produces a typical posture with an overly extended head over the shoulders, a wagging gait. Hypoplasia of the C2 odontoid process, ligamentous weakness and muscle hypotonia may predispose to atlanto-axial dislocation. Other clinical manifestations include myopia and / or retinal degeneration with retinal detachment and cleft palate. Late spondyloepiphyseal dysplasia (SEDT) is characterized by onset in adolescence and late adulthood. This results in disharmonious short stature (short torso) with protruding sternum, short neck, thoracic scoliosis or kyphosis, lumbar hyperlordosis, and early and progressive osteoarthritis of the hips and knees.