Genetics Northern California

Diastrophic Dystrophy

Diastrophic dysplasia (DD) is a short stature skeletal dysplasia characterized by significant curvatures of the spine, "hitchhiker thumbs" and cauliflower appearance of the pinnae of the ears. Individuals with DD have significant short stature with adult heights ranging from 80 to 127 cm. The limbs are extremely short in relation to the trunk. DD results in multiple joint contractures, especially of the knees and shoulders which can limit the final height and function. At birth, individuals are noted to have clubfeet, proximally displaced thumbs and big toes, and cystic masses of the outer ear (resolves spontaneously leading to the cauliflower appearance of the ear). Respiratory and spinal compression can occasionally lead to death in infancy. Once past infancy, the lifespan is normal. Intellect is normal. Extreme curves of the spine (kyphosis and scoliosis) can cause significant deformity and in 20-30% of cases causes spinal cord compression.

Cause
DD is an autosomal recessive condition. Mutations causing DD have been found in the diastrophic dysplasia sulfate transporter (DTDST) gene. These mutations result in the disruption of the assembly of cartilage matrix. There is a very wide spectrum of clinical severity. DD has an increased prevalence in the Finnish population, but can be seen in all ethnic groups.

Diagnosis
The diagnosis of DD is made by clinical and radiological (x-ray) features. DNA testing is available, but is not required for diagnosis.

Prenatal Diagnosis
Prenatal mutation testing through chorionic villus sampling (CVS) or amniocentesis is available for couples who already have a child with DD or when the mutations are known in affected parent(s). Ultrasound can often detect DD by about 16 weeks gestation. Features noted on ultrasound include short limbs, lateral projection of limbs, ulnar deviation of hands and clubfeet (talipes equinovarus).

Treatment/Services
Individuals with DD are treated symptomatically. There is no "cure" for the short stature or skeletal malformations. In infancy and early childhood, there is a risk for kyphosis of the cervical spine which can cause spinal cord compression. Children should be followed with serial cervical spine x-rays every 3-6 months until the age of 4 years. If compression is noted, an MRI should be used to evaluate further and, if compression is significant, surgery discussed. Most of these children develop some degree of thoracolumbar kyphoscoliosis (curvature of the mid-spine). If a significant curve develops, the child should be braced. If bracing fails to prevent progression of the curve, spinal fusion is usually indicated. Children with DD will almost always have gross and fine motor delays requiring physical and occupational therapy. Therapy services should pay special attention to the use of hands as the hitchhiker thumb, and general fixed extension camptodactyly can significantly limit their function. Physical therapy is also often required to address the flexion contractures. Individuals with DD often have progressive hip changes for which there has not been a standard of care for treating. Both surgery and soft tissue releases have been tried. The clubfoot in DD should be treated with corrective surgery and physical therapy. It may be resistant to correction and reoccur. Overall, a person with DD should have the fewest number of possible surgeries done as the bone in individuals with DD does not respond normally to cartilaginous damage.

Some of the most difficult aspects of having DD are not the medical issues, but rather the environmental and social issues that arise for a person of short stature and/or with an orthopedic disability. It is important to work with the family on their adjustment to the diagnosis and what that will mean for the child and their family. Individuals with DD and their families should receive assistance in developing strategies for functioning in a world made for taller people. Participation in household, school, and social activities are examples of activities that may all be significantly impacted by the condition. Stools, extenders for reaching, and extra time to get to class, are all examples of modifications that may be required. In addition to the functional aspects, being short-statured and orthopedically handicapped carries great stigma. It is important to help the people with DD and their families to mentally and emotionally prepare themselves for the teasing, staring, and ignorance they may face and to learn coping mechanisms and reactions to these behaviors. Little People of America (LPA) is the support organization for all people of short stature and their families. This organization can be extremely helpful in assisting with social adjustment and, more than anything else, letting people with short stature know that they are not alone in their circumstances.

RESOURCES

Genetics Home Reference: Diastrophic Dysplasia - General information about diastrophic dysplasia provided by the National Library of Health. Also includes links to many related sites.

Little People of America (LPA) - Provides information and support to people of short stature and their families.