Synpolydactyly 1, also known as synpolydactyly type 1, is related to pfeiffer syndrome and contractures, pterygia, and spondylocarpotarsal fusion syndrome 1a. An important gene associated with Synpolydactyly 1 is HOXD13 (Homeobox D13). Affiliated tissues include bone and t cells, and related phenotypes are 2-3 toe syndactyly and 3-4 finger syndactyly