Hyal1 knockout mice also suffer from osteoarthritis9, which is in line with the skeletal alterations seen in humans suffering from mucopolysaccharidosis IX, a HYAL1 deficiency of genetic origin9,10.Some patients with congenital HYAL1 deficiency exhibit juvenile idiopathic arthritis with proliferative synovitis, macrophage infiltration of the synovial membrane, synovial effusion and articular pain11,12. This evidence concerns the gene HYAL1 and juvenile idiopathic arthritis.