Diastrophic dysplasia

Diastrophic dysplasia: An inherited skeletal disorder involving significantly short stature (dwarfism). Characteristic features at birth include short birth length with short limbs (short-limbed dwarfism), “hitchhiker thumb”, and clubfeet. Palatal malformations such as cleft palate or submucous cleft of the palate are present in 50% of patients. There is swelling of the ears in the first days to weeks of life in 80% of children; the swelling then spontaneously subsides but later the ears have a “cauliflower” appearance. Fingers are short and broad and show ulnar deviation (are inclined away from the thumb). The thumb itself has a hitch-hiker-type appearance.

There is increased death rate in infancy due to problems breathing, but thereafter people with diastrophic dysplasia have a normal life span.

Orthopedic problems are common. The joints can be dislocated, especially the shoulder, elbows, hips, and patellae (knee caps). Flexion contractures of the knees and shoulders are common.

Scoliosis (sideways curvature of the spine) is not present at birth but often develops and is progresses particularly in the early teen years. Treatment of the scoliosis includes bracing and occasionally, spinal fusion. Progressive kyphosis (forward bending of the spine) can also occur with what is called subluxation (slippage) which can result in compression of the spinal cord.

The average length of babies with diastrophic dysplasia at birth is 16 1/2 inches (42 cms). The average adult height is slightly under 4 feet — 46-47 inches (118 cms) to be exact. The final adult height is influenced by the presence of scoliosis, hip contractures and knee contractures, and foot deformities.

Diastrophic dysplasia is inherited as an autosomal recessive condition meaning that the gene for diastrophic dysplasia is on one of the nonsex chromosomes and average-sized parents have a 1 in 4 (25%) chance of having additional children with diastrophic dysplasia.

The gene for diastrophic dysplasia is on chromosome 5q32-q33.1 and is called “diastrophic dysplasia sulfate transporter” (DTDST). Prenatal diagnosis has been performed for diastrophic dysplasia by ultrasound and by molecular DNA diagnosis to detect DTDST.

Diastrophic dysplasia was first clearly delineated by Maroteaux and Lamy in France in 1960. The term “diastrophic” was borrowed by Lamy and Maroteaux from geology: diastrophism is the process of bending of the earth’s crust by which mountains, continents, ocean basins, etc., are formed. Dysplasia means abnormal in form.