Campomelic dysplasia
| Campomelic dysplasia | |
|---|---|
| Classification and external resources | |
| Specialty | medical genetics |
| OMIM | 114290 |
| DiseasesDB | 33419 |
| MeSH | D055036 |
| Orphanet | 140 |
Campomelic dysplasia (CMD) is a rare genetic disorder characterized by bowing of the long bones and many other skeletal and extraskeletal features. It is frequently lethal in the neonatal period due to respiratory insufficiency, but the severity of the disease is variable, and some patients survive into adulthood. The name is derived from the Greek roots campo (or campto), meaning bent, and melia, meaning limb. An unusual aspect of the disease is that up to two-thirds of affected 46,XY genotypic males display a range of Disorders of Sexual Development (DSD) and genital ambiguities or may even develop as normal phenotypic females as in complete 46 XY sex reversal. An atypical form of the disease with absence of bowed limbs is called, prosaically, acampomelic campomelic dysplasia (ACD) and is found in about 10% of patients, particularly those surviving the neonatal period.
While the definitive presentation of the disease is a patient having bowed lower limbs and sex reversal in 46,XY males, there are other clinical criteria that can be used, absent these characteristics, to make the diagnosis. Patients may present with underdeveloped shoulder blades, shortened and angulated lower limbs, a vertically oriented and narrow pelvis, an enlarged head, an undersized jaw, cleft palate, flat nasal bridge, low set ears, club feet, dislocated hips, 11 pairs of ribs instead of 12, or bone abnormalities in the neck and spine. Respiratory distress can be caused by an underdeveloped trachea which collapses on inhalation or by insufficient rib cage development.
In utero sonographic diagnosis is possible when characteristic features such as bilateral bowed femurs and tibia, clubbed feet, prominent curvature of the neck, a bell-shaped chest, pelvic dilation, and/or an undersized jaw are apparent Radiographic techniques are generally used only postnatally and also rely on prototypical physical characteristics.
Genetic screening is also typically done postnatally, including PCR typing of microsatellite DNA and STS markers as well as comparative genomic hybridization (CGH) studies using DNA microarrays. In some cases PCR and sequencing of the entire SOX9 gene is used to diagnose CMD. Many different translocation breakpoints and related chromosomal aberrations in patients with CMD have been identified.
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