· heterogenous group of disorders
· primary involvement of vertebrae and epiphyseal centres
· resulting short-trunk dwarfism
· specific SED
· transmitted as autosomal dominant
· most cases sporadic (new mutation)
· disorder of growth plate
· abnormality of proliferative zone
· microcystic areas
· surrounded by ring of abnormal chondrocytes
· short limbs
· esp. proximal and middle segments
· normal hands and legs
· even shorter trunk
· neck almost absent
· cleft palate
· pectus carinatum and barrel-shaped chest
· increased lumbar lordosis
· protruberant abdomen
· hip flexion contractures
· genu valgum
· club foot
· epiphyses appear late
· platyspondyly (flat or oval vertebral bodies)
· odontoid hypoplasia
· thoracic kyphoscoliosis
· lumbar lordosis
· delayed ossification of capital femoral epiphysis
· coxa vara
· varus may progress to discontinuity of femoral neck
· may be progressive dislocation
· eye problems common
· myopia
· retinal detachment
· odontoid hypoplasia leads to instability
· may result in cervical myelopathy
· treated with posterior atlantoaxial or occipitoaxial fusion
· kyphoscoliosis usually progresses in adolescence
· should be braced early
· if fails, fusion indicated
· if coxa vara severe, intertrochanteric osteotomy indicated
· valgus and extension