Spondyloepimetaphyseal Dysplasia (SEMD) describes a heterogenous group of disorders, which have major radiological abnormalities of the spine, epiphyses, and metaphyses. Multiple forms exist and the phenotypes, modes of inheritance, and radiographic abnormalities vary considerably.
Spondyloendochromatosis; Rolland-Desbuquois Dysplasia; Wolcott-Rallisson Syndrome; Dyggve-Melchior-Clausen Syndrome; Strudwick Syndrome; Beighton Syndrome; Hall Type; Handigodu Syndrome; Iraqi Type; Missouri Type; Omani Type; Pakistani Type; SEM Sohat Type; Irapa Type; Matrilian Type; Aggrecan Type; Morquio Syndrome; Anauxetic Dysplasia; Schimke Type; Immuno-Osseous Dysplasia; Sponastrime; Silverman-Handmaker Type; Maroteaux Type SEMD.
International classification recognizes more than 15 separate entities.
Unknown. Overall incidence for acute lymphocytic leukemia (ALL) skeletal dysplasias is approximately 1/4500 births. The true incidence may be twice as high because many skeletal dysplasias do not manifest clinically until the individual is diagnosed with short stature, joint symptoms, or other complications that arise during childhood. The four most common skeletal dysplasias are thanatophoric dysplasias, achondroplasia, osteogenesis imperfecta, and achondrogenesis. Thanatophoric dysplasia and achondrogenesis account for 62% of all lethal skeletal dysplasias. Lethal skeletal dysplasias are estimated to occur in 0.95 per 10,000 live births. Achondroplasia is the most common nonlethal skeletal dysplasia.
Autosomal dominant and autosomal recessive transmission most frequently. X-linked SEMD described.
Skeletal dysplasias are characterized by abnormal growth of bone and cartilage.
Clinical syndromes with characteristic radiological findings. In utero ultrasonography may identify limb abnormalities but is not diagnostic.
The clinical features depend on the type of SEMD and the age of the patient. (See Table S-3).
SEMD, Strudwick Type: Presents at birth with cleft palate, short limbs and trunk, protruding abdomen, and respiratory distress secondary to small chest with short ribs. Other clinical features include hypertelorism and a flat face. Intelligence and life expectancy are normal. Features occurring later on in life include severe coxa vara (with possible dislocation), a waddling gait, lumbar hyperlordosis (platy- and anisospondyly) and myopia with retinal detachment. Before these children reach school age, the characteristic changes in the metaphyses of the long bones become evident, which usually affect the ulna more severely than radius, fibula, or tibia. The disorder manifests as fragmentation of the long bone metaphyses mixed with areas of sclerosis. Lung function tends to remain compromised, even more so if kyphoscoliosis develops. Cervical spine instability may be present because of hypoplasia of C3 and/or the odontoid process.
SEMD with Joint Laxity (SEMD-JL), Beighton Type: Characterized by short stature, mental retardation, joint and ligamentous laxity with dislocations (eg, hips, radial heads). Kyphoscoliosis is already present at birth, may progress rapidly, and lead to significant cardiopulmonary changes (cor pulmonale) and even paraplegia. ...