Classification

 DA1: distal arthrogryposis type 1 (MIM.108120)
 DA2A: distal arthrogryposis type 2A (MIM.193700)
 DA2B: distal arthrogryposis type 2B (ch. 11) (MIM.601680)
 DA2C: distal arthrogryposis type 2C
 DA2D: distal arthrogryposis type 2D
 DA3: distal arthrogryposis type 3 (Gordon syndrome) (MIM.114300) (camptodactyly, cleft palate and club-foot)
 DA4: distal arthrogryposis type 4
 DA5: distal arthrogryposis type 5

Etiology

 mutations in TNNI2 (#12592607#)

• TNNI2 encodes an isoform of troponin I; this isoform and the isoforms of troponin T (TnT) and troponin C constitute the troponin complex of fast-twitch myofibers. This complex is the primary sensor of intracellular Ca+2 ion concentration in skeletal muscle, and, consequently, it is an important regulator of muscle contraction.

 mutations in TPM2
 TNNT3 (gene encoding TnT specific to fast-twitch myofibers) (DA2B) (#12865991#)

 in syndromes

• Prader-Willi syndrome (#15510104#)
• velocardiofacial syndrome (#15346917#, #15042364#)
• mosaic tetrasomy 10p (#12599193#)
• Proteus syndrome (#9457508#)

The troponin complex of fast-twitch myofibers exerts its effect on muscle contraction by binding to actin and beta-tropomyosin, the product encoded by TPM2 (Clark et al. 2002).

References

 Bamshad M, Jorde LB, Carey JC. A revised and extended classification of the distal arthrogryposes. Am J Med Genet. 1996 Nov 11;65(4):277-81. PMID: #8923935#