To date, BHLHA9 has been implicated in three distinct limb phenotypes: split-hand/foot malformation with long bone deficiency (SHFLD3, OMIM#612576), complex camptosynpolydactyly (OMIM#607539), and MSSD. This evidence concerns the gene BHLHA9 and mesoaxial synostotic syndactyly with phalangeal reduction.