Mutations in the Homeodomain of HOXD13 Cause Syndactyly Type 1-c in Two Chinese Families

Background: Syndactyly type 1 (SD1) is an autosomal dominant limb malformation characterized in its classical form by complete or partial webbing between the third and fourth fingers and/or the second and third toes. Its four subtypes (a, b, c, and d) are defined based on variable phenotypes, but the responsible gene is yet to be identified. SD1-a has been mapped to chromosome 3p21.31 and SD1-b to 2q34-q36. SD1-c and SD1-d are very rare and, to our knowledge, no gene loci have been identified.