COL2A1 and spondyloepiphyseal dysplasia congenita: Thirdly, 52 heterozygous variants were predicted to be deleterious by software such as SIFT, MutationTaster, Polyphen2, Phylop, GERP et al. Among these variants, COL2A1 G504S was the only one which was associated with SEDC and hearing loss by checking for disease and gene-specific databases (see Additional File 2: Fig. S1 and Additional File 1: Table S2).