Distal arthrogryposis type 1

Distal arthrogryposis type 1 (DA1), also known as digitotalar dysmorphism or distal arthrogryposis type 1A, is a rare inherited condition characterized by congenital contractures (stiffness) primarily affecting the hands and feet. It is one of the most common forms of distal arthrogryposis, a group of disorders in which joint contractures are present at birth and predominantly involve the distal (far) parts of the limbs. Key features include camptodactyly (permanently bent fingers, especially the overlapping of fingers), ulnar deviation of the fingers, and talipes equinovarus (clubfoot). Affected individuals typically have clenched fists at birth with overlapping fingers, and the feet may show positional deformities including metatarsus varus. Unlike some other forms of arthrogryposis, DA1 does not typically involve other organ systems, and intellectual development is normal. The condition is caused by mutations in genes encoding components of the contractile apparatus of muscle fibers. Mutations in the TPM2 gene (encoding beta-tropomyosin) and the MYH3 gene (encoding embryonic myosin heavy chain) are among the most commonly identified genetic causes. Other genes implicated include MYBPC1 and MYH3. The contractures result from reduced fetal movement during development due to impaired muscle function. Treatment for DA1 is primarily supportive and focuses on improving joint mobility and function. Early intervention with physical therapy, serial casting, and splinting can significantly improve range of motion in affected joints. Occupational therapy helps optimize hand function. Surgical correction may be necessary for severe clubfoot or persistent hand contractures that do not respond to conservative measures. The prognosis is generally favorable, as many contractures improve with age and treatment, and most individuals achieve good functional outcomes. Life expectancy is normal.

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