Syndactyly, Mesoaxial Synostotic, with Phalangeal Reduction, also known as mesoaxial synostotic syndactyly with phalangeal reduction, is related to polydactyly and camptosynpolydactyly, complex. An important gene associated with Syndactyly, Mesoaxial Synostotic, with Phalangeal Reduction is BHLHA9 (Basic Helix-Loop-Helix Family Member A9). Affiliated tissues include bone and heart, and related phenotypes are clinodactyly of the 5th finger and short thumb