MPS IX: an overview
As the rarest mucopolysaccharidosis (MPS) disorder, MPS IX has limited information and very few management guidelines1
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
- Symptoms appear at varying ages1,2
- Presentations observed to date include:1,2
- Selective joint pain
- Swelling and reduced range of motion
- Hyperextensible joints
- Short stature has been reported in one case
- Suspicion of MPS IX should be raised in patients with chronic joint pain unresponsive to anti-inflammatory drugs, a family history of similarly affected children and/or MRI showing proliferative synovitis without erosions
- Overall disease burden: patients experience chronic joint pain, effusions, cysts, gait abnormalities, and reduced range of motion1,2
- Joint problems may progressively worsen due to the continued accumulation of GAGs in the affected tissues2
- MPS IX is caused by a genetic mutation in the HYAL1 gene1
- There are 2 known pathogenic variants within HYAL13
- Mutations in HYAL1 and resulting enzyme deficiency leads to accumulation of the GAG hyaluronan1,2
Key management considerations
- There are currently no approved therapies for the treatment of MPS IX.
- Available treatment and management recommendations:
- 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.
- Natowicz MR, et al. Clinical and biochemical manifestations of hyaluronidase deficiency. N Engl J Med. 1996;335(14):1029-1033.