distal arthrogryposis type 1
Distal arthrogryposis type 1 is a disorder characterized by joint deformities (contractures) that restrict movement in the hands and feet. The term "arthrogryposis" comes from the Greek words for joint (arthro-) and crooked or hooked (gryposis). The characteristic features of this condition include permanently bent fingers and toes (camptodactyly), overlapping fingers, and a hand deformity in which all of the fingers are angled outward toward the fifth finger (ulnar deviation). Clubfoot, which is an inward- and upward-turning foot, is also commonly seen with distal arthrogryposis type 1. The specific hand and foot abnormalities vary among affected individuals. However, this condition typically does not cause any signs and symptoms affecting other parts of the body.
Distal arthrogryposis type 1 affects an estimated 1 in 10,000 people worldwide.
Distal arthrogryposis type 1 can be caused by mutations in at least two genes: TPM2 and MYBPC1. These genes are active (expressed) in muscle cells, where they interact with other muscle proteins to help regulate the tensing of muscle fibers (muscle contraction). It is unclear how mutations in the TPM2 and MYBPC1 genes lead to the joint abnormalities characteristic of distal arthrogryposis type 1. However, researchers speculate that contractures may be related to problems with muscle contraction that limit the movement of joints before birth.
In some cases, the genetic cause of distal arthrogryposis type 1 is unknown. Researchers are looking for additional genetic changes that may be responsible for this condition.
This condition is inherited in an autosomal dominant pattern, which means one copy of an altered gene in each cell is sufficient to cause the disorder. In many cases, a person with distal arthrogryposis type 1 has a parent and other close family members with the condition.
- arthrogryposis, distal, type 1