ACAN and spondyloepimetaphyseal dysplasia: ACAN heterozygous variants can cause spondyloepiphyseal dysplasia, kimberley type (SEDK) (3); short stature and advanced bone age, with or without early-onset osteoarthritis (OA) and/or osteochondritis dissecans (OCD), while homozygous or compound heterozygous mutations in ACAN are associated with spondyloepimetaphyseal dysplasia, aggrecan type (SEMD) (4).