Troponin I, fast skeletal muscle (troponin I FS) is the inhibitory subunit of troponin, the thin filament regulatory comple, Xenopus/Amphibian, which confers calcium-sensitivity to striated muscle actomyosin ATPase activity. Defects in troponin I FS are a cause of distal arthrogryposis type 2B (DA2B), also known as arthrogryposis multiple, Xenopus/Amphibian, congenita, distal, type 2B (AMCD2B). DA2B is a form of inherited multiple congenital contractures. Affected individuals have vertical talus, ulnar deviation in the hands, severe camptodactyly, and a distinctive face characterized by a triangular shape,Porcinerominent nasolabial folds, small mouth and a prominent chin.