Hyaluronidase deficiency, also known as Mucopolysaccharidosis type IX or MPS IX, is a condition caused by mutations in the HYAL1 gene, and is characterized by multiple soft-tissue masses.

[1]: 544 As hyaluronidase deficiency is an extremely rare disorder, a clear clinical picture of the disease has not been formed.

However, the following symptoms may occur:[2] It is diagnosed through a combination of a thorough clinical evaluation in which characteristic findings are identified, specialized tests that can detect things like excessive levels of mucopolysaccharides and enzym essays to see if there is a deficiency in the enzyme hyaluronidase.

[4] At the moment, there are no effective treatments against hyaluronidase deficiency.

The only treatment they can provide is symptomatic and meant to manage and alleviate individual symptoms.