Sandhoff disease is caused by mutations in the HEXB gene causes Sandhoff disease. The gene provides instructions for making a protein crucial to the enzymes Hex-A and Hex-B which function in nerve cells to break down fatty substances, complex sugars, and molecules that are linked to sugars. In particular, Hex-A breaks down a fatty compound called GM2 ganglioside. Mutations in the HEXB gene disrupt the activity of these enzymes, preventing the breakdown of GM2 and other molecules. As a result, progressive damage caused by the resulting buildup of GM2 leads to the destruction of nerve cells.
Sandhoff disease symptoms are clinically very similar to Tay-Sachs. The classic infantile form of the disease has the most severe symptoms and is incredibly hard to diagnose at an early age. Adult and juvenile forms of Sandhoff disease are more rare than the infantile form and in these cases individuals suffer cognitive problems and a loss of muscle coordination that eventually destroys their ability to walk. As in Tay-Sachs, younger suffers of Sandhoff have a limited life expectancy as the disease progresses.
Infantile onset
The most common form of Sandhoff disease.
Adult onset
The rarest form of Sandhoff disease.
Juvenile onset
This form presents in childhood.
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As a rare autosomal recessive neurodegenerative disorder, Sandhoff is clinically almost indistinguishable from Tay–Sachs disease, another genetic disorder that disrupts beta-hexosaminidases A and B. There are three subsets of Sandhoff disease based on when first symptoms appear: classic infantile, juvenile and adult late onset.
Autosomes are the non-sex-related chromosomes. The term autosomal recessive inheritance means that the effects of possessing a single copy of a disease-causing gene are hidden. With a recessive condition, a person may be a carrier of a disease gene, but may have no noticeable effect on their everyday health. A positive diagnosis of Sandhoff in an individual means that each parent is a carrier of a disease-causing mutation on the specific gene which causes the disease.