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Diseases

Genetic and Rare Diseases Information Center (GARD)

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Sandhoff disease


Other Names for this Disease
  • Beta-hexosaminidase-beta-subunit deficiency
  • GM2 gangliosidosis, type 2
  • Hexosaminidase A and B deficiency Disease
  • Sandhoff-Jatzkewitz-Pilz disease
  • Total hexosaminidase deficiency
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Overview



What is Sandhoff disease?

What are the signs and symptoms of Sandhoff disease?

What causes Sandhoff disease?

How is Sandhoff disease inherited?


What is Sandhoff disease?

Sandhoff disease is an inherited lipid storage disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord.[1][2] The most common and severe form of Sandhoff disease becomes apparent in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months when their development slows and muscles used for movement weaken. Other forms of Sandhoff disease have been described where much milder signs and symptoms begin in childhood, adolescence, or adulthood. These forms are very rare. Sandhoff disease is caused by mutations in the HEXB gene.[1] These mutations cause a deficiency of the enzyme beta-hexosaminidase, which results in the accumulation of certain fats (lipids) in the brain and other organs of the body.[2] Sandhoff disease is inherited in an autosomal recessive manner.[1] 
Last updated: 10/19/2011

What are the signs and symptoms of Sandhoff disease?

Infants with the classic form of Sandhoff disease typically appear normal until the age of 3 to 6 months when their development slows and muscles used for movement weaken. Affected infants typically lose motor skills such as turning over, sitting, and crawling. They may also develop an exaggerated startle reaction to loud noises. As the disease progresses, children with Sandhoff disease may experience seizures, vision and hearing loss, intellectual disability, and paralysis. An eye abnormality called a cherry-red spot, which can be identified through an eye examination, is characteristic of this disorder. Some affected children also have an enlarged liver and spleen, frequent respiratory infections, or bone abnormalities.[1][2] Children with the severe infantile form of Sandhoff disease usually live only into early childhood.[1]

Forms of Sandhoff disease where the symptoms develop after infancy are very rare. Signs and symptoms can begin in childhood, adolescence, or adulthood and are usually milder than those seen with the infantile form. Characteristic features include muscle weakness, loss of muscle coordination (ataxia) and other problems with movement, speech problems, and mental illness. These signs and symptoms vary widely among people with late-onset forms of Sandhoff disease.[1]

Last updated: 2/2/2011

What causes Sandhoff disease?

Sandhoff disease is caused by mutations in the HEXB gene. The HEXB gene provides instructions for making a protein that is part of two critical enzymes in the nervous system, beta-hexosaminidase A and beta-hexosaminidase B. These enzymes are located in lysosomes, which are structures in cells that break down toxic substances and act as recycling centers. Within lysosomes, these enzymes break down fatty substances, complex sugars, and molecules that are linked to sugars. In particular, beta-hexosaminidase A helps break down a fatty substance called GM2 ganglioside.[1]

Mutations in the HEXB gene disrupt the activity of beta-hexosaminidase A and beta-hexosaminidase B, which prevents these enzymes from breaking down GM2 ganglioside and other molecules. As a result, these compounds can accumulate to toxic levels, particularly in neurons of the brain and spinal cord. A buildup of GM2 ganglioside leads to the progressive destruction of these neurons, which causes many of the signs and symptoms of Sandhoff disease.[1]

Last updated: 2/2/2011

How is Sandhoff disease inherited?

Sandhoff disease is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.[1] 
Last updated: 8/22/2011

References
  1. Sandhoff disease. Genetics Home Reference (GHR). 2008; http://ghr.nlm.nih.gov/condition/sandhoff-disease. Accessed 10/19/2011.
  2. NINDS Sandhoff Disease Information Page. National Institute of Neurological Disorders and Stroke (NINDS). 2011; http://www.ninds.nih.gov/disorders/sandhoff/sandhoff.htm. Accessed 10/19/2011.