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

HEXB gene

The HEXB gene provides instructions for the beta subunit of two essential enzymes, beta-hexosaminidase A and B, which are responsible for breaking down fatty compounds and sugars in the nervous system.

Normal Function

The HEXB gene provides instructions for making a protein that is one part (the beta subunit) of two related enzymes: beta-hexosaminidase A and beta-hexosaminidase B.

  • Beta-hexosaminidase A: Includes one alpha subunit (from the HEXA gene) and one beta subunit.
  • Beta-hexosaminidase B: Composed of two beta subunits.

These enzymes play a critical role in nerve cells (neurons) in the brain and spinal cord. They are found in lysosomes, where they break down fatty compounds called sphingolipids, complex sugars called oligosaccharides, and molecules linked to sugars (such as glycoproteins). Beta-hexosaminidase A specifically helps break down the fatty substance GM2 ganglioside.

Health Conditions Related to Genetic Changes

Sandhoff disease

Sandhoff disease is caused by variants in the HEXB gene. These variants reduce or eliminate the activity of both beta-hexosaminidase A and beta-hexosaminidase B. A reduction in enzyme activity results in an inability to properly break down GM2 ganglioside and other molecules, which allows these compounds to accumulate within cells.

Increased levels of GM2 ganglioside are particularly toxic to neurons in the central nervous system. Excess GM2 ganglioside leads to the progressive destruction of these cells, which causes many of the characteristic features of Sandhoff disease.

  • Severe (infantile) form: Most known variants prevent cells from making any functional beta-hexosaminidase A or B, or lead to the production of completely nonfunctional versions. The most common variant deletes a large segment of DNA near the beginning of the HEXB gene.
  • Less severe forms: Other variants reduce but do not eliminate the activity of the enzymes, leading to forms of the disease that appear later in life.

Other Names for This Gene

  • beta-N-acetylhexosaminidase B
  • ENC-1AS
  • Hex B
  • HEXB_HUMAN
  • hexosaminidase B
  • hexosaminidase B (beta polypeptide)

Frequently Asked Questions

Currently, there is no cure for Sandhoff disease. Treatment focuses on supportive care to manage symptoms and improve quality of life. This can include medications to control seizures, manage muscle spasticity, and address feeding difficulties. Physical, occupational, and speech therapies are also important to help maintain function and comfort as the disease progresses.
In the severe infantile form of Sandhoff disease, symptoms usually appear around 3 to 6 months of age. Early signs can include an exaggerated startle response to noise, muscle weakness, feeding difficulties, and developmental delays (e.g., not meeting milestones like sitting or crawling). As the disease progresses, infants develop increasing muscle weakness, loss of motor skills, seizures, and vision/hearing loss, leading to a severe decline in neurological function.
Sandhoff disease is typically diagnosed through enzyme assays that measure the activity of beta-hexosaminidase A and B in blood or other tissues. If enzyme activity is significantly reduced, genetic testing of the HEXB gene can confirm the diagnosis and identify the specific mutations. Carrier screening is available for family members, especially those with a known family history, to determine if they carry one copy of a HEXB mutation and are at risk of passing it on to their children.
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.

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