Diastrophic dysplasia

Diastrophic dysplasia (DTD), also known as diastrophic dwarfism, is a rare autosomal recessive skeletal disorder caused by mutations in the SLC26A2 gene (formerly known as DTDST), which encodes a sulfate transporter essential for cartilage and bone development. The condition is present at birth and is characterized by short-limbed short stature, joint contractures, progressive kyphoscoliosis (curvature of the spine), bilateral clubfoot (talipes equinovarus), and a distinctive "hitchhiker thumb" deformity caused by a short, abducted first metacarpal. A hallmark feature in newborns is cystic swelling of the external ears ("cauliflower ear" deformity), which can develop into calcified, thickened pinnae over time. Cleft palate occurs in a significant proportion of affected individuals. The disorder affects the skeletal system broadly, including the spine, limbs, hands, feet, and joints. Progressive joint degeneration and contractures can lead to significant mobility limitations over time. Cervical spine abnormalities, including cervical kyphosis and spinal stenosis, may pose serious neurological risks. Intelligence is typically normal. Respiratory complications may occur in infancy due to small airways and chest wall abnormalities, but with appropriate management, life expectancy can be near normal. There is currently no cure for diastrophic dysplasia. Treatment is supportive and multidisciplinary, involving orthopedic interventions for clubfoot, scoliosis, and joint contractures, as well as physical therapy to maintain mobility. Surgical correction of spinal deformities may be necessary. Monitoring for cervical spine instability and spinal cord compression is important. Cleft palate repair and hearing assessments should be performed as needed. The condition is most prevalent in Finland due to a founder effect, where the carrier frequency is approximately 1 in 70.

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