A rare primary bone dysplasia characterised by severe early-onset dysplasia of the proximal femurs, with almost complete absence of the secondary ossification centres and abnormal development of the femoral necks (short and broad with irregular metaphyses). It is associated with gait abnormality, mild short stature, arthralgia, and joint stiffness with limited mobility of the hips and irregular acetabula, and hip and knee pain. Coxa vara and mild spinal changes are also associated. [from
SNOMEDCT_US]