Spondyloepiphyseal dysplasia (SED) is an inherited disorder of bone growth. SED affects the growth of the spine (spondylo) and the ends (epiphyseal) of the bones in the arms and legs. Affected indiviuals have short stature, with a shortened trunk and shortened limbs.
SED is quite rare and is caused by mutations to the COL2A1 gene. This gene is important for the normal formation of cartilage. The condition is inherited in an autosomal dominant pattern; only one allele copy is required to express the disorder.
SED leads to a very significant short stature combined with lower limb deformities and progressive deformation of the joints. The short stature involves both shortness of the trunk as well as shortening of the lower limbs. The lengthening, if it is performed, does not improve disproportion as it does in Achondroplasia because the trunk is short and no lengthening of the trunk is performed.
The problems these patients have are related to the severe flexion deformity of the hips with hyperlordosis. At the knees, they typically have genu valgum. At the ankles, they frequently have valgus deformities.