COL2A1 and mild spondyloepiphyseal dysplasia due to COL2A1 mutation with early-onset osteoarthritis: Chinese patients with OSCDP, Czech dysplasia and EDMMD caused by COL2A1 mutations were first reported, expanding the spectrum of COL2A1 mutations and the phenotype of COL2A1-related disorders and providing further evidence for the phenotype-genotype relations, which may help improve procreative management of COL2A1-related disorders.