GDF5 and brachydactyly: Some loss‐of‐function GDF5 variants result in reduced osteogenesis or abnormal bone development, such as brachydactyly (BD), whereas some gain‐of‐function GDF5 variants cause proximal symphalangism (SYM1, OMIM #185800) and multiple‐synostoses syndrome 2 (SYNS2, OMIM #610017).