Spondyloepiphyseal dysplasia [SED] is characterized by disproportionate dwarfism with progressive involvement of the spine and epiphyses of the long bones.

There are two types of SED. The congenita type is detectable at birth, whereas a milder tarda type presents later in childhood.

Spondyloepiphyseal dysplasia congenita results in short-trunk dwarfism and variable degrees of coxa vara, with abnormal epiphyses and vertebral flattening. Shortening is rhizomelic and mesomelic, with relative sparing of the hands and feet.

Spondyloepiphyseal dysplasia tarda is a milder form of SED that is not clinically apparent at birth. Most patients present in older childhood or adolescence with complaints of hip pain.

SED congenita is transmitted by autosomal dominant inheritance but most cases are sporadic.

It is caused by mutations in the COL2A1 locus on chromosome 12, which encodes the type II procollagen α1 chain.

SED tarda is transmitted either by autosomal recessive or X-linked recessive.

The X- linked form has been mapped to the SEDL gene in the Xp22 region.

SED congenita –

Short stature

Eyes are wide-set

Neck is short

The chest appears barrel-shaped

Angular deformity, particular genu valgum is common

Lumbar lordosis may be accentuated and is usually due to hip flexion contractures

Waddling gait is produced by coxa vara

Club foot deformity may be seen.

Associated anomalies are cleft palate, myopia with retinal detachment, cataracts, deafness, herniae, and nephrotic syndrome.

SED tarda –

Not recognized at birth, but becomes apparent as the growth rate of the child slows in mid-childhood or adolescence.

The usual presenting complaint is either short stature or hip pain.

The X-linked recessive form affects only boys and is characterized by diminished height, barrel chest deformity, and early hip arthrosis.

SED congenita –

Delayed appearance of the epiphyses, when the epiphyses do appear, they are flattened and irregular in shape.

Femoral heads are not apparent on radiographs until the patient is approximately 5 years of age.

Ossification centers of the carpals and tarsals are delayed, as are the secondary centers of ossification of the long tubular bones

Coxa vara is present

Platyspondyly is seen, and kyphoscoliosis and odontoid hypoplasia may be present.

SED tarda –

Radiographic features similar to Perthes disease however, there will be symmetric involvement.

Platyspondyly with the appearance of a protruding hump and narrow disc spaces of the spine.

Genetic testing can be performed to identify the mutations.

SED Congenita –

Spine –

Cervical spine instability – Laminectomy of C1 combined with occiput – C2 fusion is the preferred treatment.

Basilar invagination – Posterior fossa decompression and occipitocervical fusion, with prolonged external immobilization.

Scoliosis – Bracing, fusion, and instrumentation are the options of treatment.

Lumbar hyperlordosis – Does not require spinal surgery.

Lower extremities –

Coxa vara – Valgus osteotomy of the proximal femur.

Hip dislocation with coxa vara – Open reduction with femoral and acetabular osteotomies is preferred.

Genu valgum – Distal femur varus osteotomy or guided growth is preferred.

Pain and joint problems – Premature osteoarthritis

SED tarda –

Precocious hip arthritis – Valgus osteotomy of the proximal femur with acetabular augmentation

Degenerative arthritis – Total joint arthroplasty