Most non-syndromic synpolydactyly cosegregates with a mutation in the HOXD13 gene on chromosome 2q31 and is categorized as Synpolydactyly type 1 (SPD1, OMIM 186000), which is also known as syndactyly type II (SD II), according to the nomenclature of Temtamy and McKuisck (Temtamy and McKusick, 1978). This evidence concerns the gene HOXD13 and synpolydactyly.