MPS IX, also known at Natowicz syndrome, is caused by a deficiency of the enzyme hyaluronidase, which is required for the degradation of the glycosaminoglycan (GAG) hyaluronan. This GAG is highly expressed in synovial fluid, cartilage, and skin, leading to progressive joint manifestations.1,2
MPS IX can present at varying ages with chronic joint pain unresponsive to anti-inflammatory medication.1,2
References: 1. Imundo L et al. A complete deficiency of Hyaluronoglucosaminidase 1 (HYAL1) presenting as familial juvenile idiopathic arthritis. J Inherit Metab Dis 2011;34(5):1013–1022. 2. Natowicz MR et al. Clinical and biochemical manifestations of hyaluronidase deficiency. N Engl J Med 1996;335(14):1029–1033. 3. Triggs-Raine B et al. Mutations in HYAL1, a member of a tandemly distributed multigene family encoding disparate hyaluronidase activities, cause a newly described lysosomal disorder, mucopolysaccharidosis IX. Proc Natl Acad Sci USA 1999;96(11):6296–6300.