Loss of cartilage integrity in children with arthritis is probably associated with impaired aggrecan function due to either the proteolytic cleavage of the aggrecan core protein, which decreases aggrecan charge (CS and KS chains are released), or to the cleavage of HAPLN1 and HA, which decreases aggregate size or reduces its synthesis [6,7]. Here, ACAN is linked to arthritic joint disease.