Mutations in the aggrecan core protein gene have been identified in human skeletal disorders including: spondyloepimetaphyseal dysplasia with premature and severe osteoarthritis and osteochondritis (Gleghorn et al., 2005) and the recessive skeletal dysplasia EMD aggrecan-type which results from a missence mutation affecting the C-type lectin domain of aggrecan (Tompson et al., 2009; Stattin et al., 2010). Here, ACAN is linked to spondyloepimetaphyseal dysplasia, matrilin-3 type.