Exome Sequencing Identifies a Dominant <b><i>TNNT3</i></b> Mutation in a Large Family with Distal Arthrogryposis

Distal arthrogryposis (DA) is a group of rare, clinically and genetically heterogeneous disorders primarily characterized by congenital contractures of the distal limb joints without a neuromuscular disease. Mutations in at least 8 different genes have been shown to cause DA. Here, we report a 4-generation Indian family with 18 affected members presenting variable features of camptodactyly, brachydactyly, syndactyly, decreased flexion palmar creases, ulnar deviation of the hands, sandal gaps and club feet. We undertook exome sequencing of 3 distantly related affected individuals. Bioinformatics filtering revealed a known pathogenic missense mutation c.188G>A (p.Arg63His) in TNNT3 in all 3 affected individuals that segregated with the phenotype. The affected individuals exhibit significant phenotypic variability. This study demonstrates the value of exome sequencing helping to define the causative variant in genetically heterogeneous disorders.