This is a rare genetic condition characterized by the short-limbed dwarfism, abnormal development of the bones and the joints. This is a congenital disorder that is evident at the birth of the infant who is born short, around 16.5 inches long rather than the standard 19 and 21 inches. However, the severity of the condition tends to vary between each case. These children usually exhibit normal intelligence but their developmental milestones such as rolling and sitting may be attained much later than other children. The exact prevalence of this disorder is not known but research estimates it can affect 1 in 100,000 infants.
Causes
Diastrophic dysplasia develops as the result of the mutation in the SLC26A2 gene which produces a protein that is vital for the development of cartilage and the bone. The mutation in this gene affects the structure of developing cartilage and as the result; the bones are not properly formed. This consequently results in the skeletal features that are characteristic of this condition. Diastrophic dysplasia is inherited in an autosomal recessive pattern meaning both the copies of the gene present in each cell are defective. The parents may each be the carrier of one copy of the defective gene without presenting any symptoms of this disorder.
Symptoms
The newborns and children present short, bowed arms and legs with short stature. The malformations of the bones of the limbs and other parts of the body may include first bone of each hand that may be usually short with abnormally short digits and the joints between certain bones of the digits may also be fused (symphalangism) resulting in reduced mobility. The severe foot deformities may also be evident as the result of an abnormal fusion of bones of each foot. Partial or complete dislocation of certain joints of the body is also evident. They may also be predisposed to osteoarthrosis of certain joints causing pain, tenderness, stiffness or deformity in some cases. Abnormal bones within the spinal column can occur such as incomplete closure of vertebrae within the neck area. They can develop abnormal sideway curvature of the spine and the front-to-back curvature of the spine. Some of the cases experience partial dislocation of joints that can create a compression of the spinal cord. The hearing is usually normal but may experience hearing impairment resulting from the abnormal fusion of three tiny bones in the middle ear. Additional malformation of the head and face includes the high prominent forehead, abnormally small jaw and high arched palate and cleft palate. They are prone to develop life-threatening complications from respiratory obstruction and respiratory distress may also occur.
Diagnosis
It is possible to detect this disorder prenatally during early pregnancy with genetic testing particularly when individuals present the family history of this condition. It can also be confirmed at birth with the physical findings characteristics of this disorder. The imaging tests such as CT scan can identify various skeletal abnormalities associated with diastrophic dysplasia. Other tests may be necessary to detect various abnormalities such as hearing defects with audiological tests that can occur in children with this disorder.
Treatment
The treatment for this disorder is based on the specific symptoms that are evident in different cases. This usually includes the coordinated efforts of a team of specialists to devise an effective treatment plan for the children. In some cases, careful monitoring is all that is needed, while others may require surgical intervention for corrective procedures to address the malformations. This can include the surgical options for spinal fusion, physical therapy and nonsurgical option such as bracing. Careful monitoring is essential to ensure corrective treatment is delivered for conditions such as respiratory obstruction and distress that can develop.
References
https://rarediseases.org/rare-diseases/diastrophic-dysplasia/
https://ghr.nlm.nih.gov/condition/diastrophic-dysplasia#inheritance
http://www.chop.edu/conditions-diseases/diastrophic-dysplasia
