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GUSB gene

Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

GUSB gene

The GUSB gene provides instructions for the enzyme beta-glucuronidase, which is essential for breaking down complex sugar molecules within cells.

Normal Function

The GUSB gene provides instructions for producing an enzyme called beta-glucuronidase (β-glucuronidase). This enzyme is located in lysosomes, the cell's recycling centers. Its primary role is to break down large molecules called glycosaminoglycans (GAGs), which are long chains of sugar molecules. Specifically, beta-glucuronidase removes the sugar glucuronic acid from the ends of three types of GAGs: dermatan sulfate, heparan sulfate, and chondroitin sulfate.

Health Conditions Related to Genetic Changes

Mucopolysaccharidosis type VII

Mucopolysaccharidosis type VII (MPS VII) is caused by mutations in the GUSB gene that reduce or eliminate the function of the beta-glucuronidase enzyme. This deficiency prevents the proper breakdown of dermatan sulfate, heparan sulfate, and chondroitin sulfate.

As a result, these GAGs accumulate within the lysosomes of tissues and organs throughout the body. This buildup causes the lysosomes to enlarge, leading to the following effects:

  • Enlargement of many tissues and organs
  • Potential interference with the function of other proteins inside the lysosomes
  • Disruption of normal cellular functions

Frequently Asked Questions

MPS VII can present with subtle features such as a large head (macrocephaly), a slightly enlarged liver or spleen (hepatosplenomegaly), and mild joint stiffness. In infancy, a child may have a soft, floppy appearance, feeding difficulties, and a mild delay in motor milestones. These signs are often nonspecific, so a high index of suspicion is needed, especially if there is a family history of lysosomal storage disorders.
The definitive diagnosis involves a combination of biochemical and genetic testing. First, a urine test for elevated glycosaminoglycans (GAGs) is performed. If GAGs are high, a leukocyte or fibroblast beta‑glucuronidase activity assay is done to measure enzyme function. A normal or reduced activity is then followed by sequencing of the GUSB gene to identify pathogenic variants. Whole‑exome sequencing or targeted panels can also detect compound heterozygous mutations.
Enzyme replacement therapy (ERT) with recombinant beta‑glucuronidase is the mainstay of treatment and can reduce organ enlargement and improve growth. Hematopoietic stem cell transplantation (HSCT) may be considered in severe cases, especially if performed early. Supportive care—including physical therapy, cardiac monitoring, and management of airway obstruction—is essential. Gene therapy trials are also underway and may become an option in the future.
With early diagnosis and timely ERT, many patients experience improved growth, reduced organomegaly, and better quality of life. However, neurological involvement can still progress, and life expectancy varies widely. Regular monitoring for cardiac, respiratory, and skeletal complications is crucial, and multidisciplinary care improves outcomes. The prognosis is better when treatment starts before significant organ damage has occurred.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.