TNNI2 encodes troponin I2, the inhibitory subunit of the troponin complex in fast skeletal muscle thin filaments 1. TNNI2 functions as a calcium-regulated inhibitor of muscle contraction, playing a central role in regulating the sensitivity of the actomyosin ATPase to calcium 1. The gene is located at chromosome 11.5 and is organized as a gene pair with TNNT3 (fast skeletal troponin T), reflecting a conserved evolutionary arrangement of troponin genes 23. Pathogenic TNNI2 variants cause distal arthrogryposis type 2B (DA2B), a congenital disorder characterized by multiple joint contractures of the hands and feet 45. DA2B is inherited in an autosomal dominant pattern, with mutations in TNNI2, MYH3, or TNNT3 identified in approximately 50% of Sheldon-Hall syndrome cases, the prototypical distal arthrogryposis syndrome 6. Specific TNNI2 variants (c.525G>T and c.532T>C) have been associated with DA2B phenotypes 45. Contractures are typically most severe at birth and non-progressive, with affected individuals having normal life expectancy and cognitive abilities 6. Management involves physical therapy, serial casting, and surgical intervention rather than specific pharmacotherapy.