Tay-Sachs Disease (TSD) is a genetic disorder that destroys the nerve cells in the brain and spinal cord, resulting in a decline in mental and physical function, such that a person with TSD is ultimately unable to breathe or swallow. The disease is rare in the general population, and pretty much only seen in certain ancestry groups, such as people from French-Canadian and Ashkenazi Jewish descent or those from eastern and central Europe.
Types of the Disease
There are three types of the disease. The most common form is infantile TSD that manifests at approximately six months of age. This leads to a rapid mental and physical decline in the infant. The second form is juvenile TSD, which becomes apparent between the ages of 2 to 10. Finally, there is late-onset TSD, which occurs in patients in their 20s to early 30s. Because of the myriad symptoms presented, late-onset TSD is frequently misdiagnosed, but unlike the other two forms, it is usually non-fatal.
Causes of Tay-Sachs
Tay-Sachs disease is caused by mutations in the hexosaminidase A (alpha polypeptide) gene (HEXA), an autosomal gene that is located on chromosome 15. In its normal function, HEXA produces the alpha subunit of the enzyme beta-hexosaminidase A. The enzyme is a key component in lysosomes in the brain and spinal cord that allows for the break down of GM2 ganglioside, a lipid-based substance.
Without a functioning HEXA gene, the GM2 ganglioside in the body accumulates, eventually reaching toxic levels within the body. This, in turn, leads to the death of neurons in the brain and spinal cord, causing the symptoms seen in Tay-Sachs disease.
Symptoms of Tay-Sachs
In infantile TSD, the initial symptoms do not appear to be obvious. The baby develops normally for about three to six months, before it becomes apparent that the child is not developing as rapidly as he or she ought to be. As the child grows, the symptoms become more apparent, taking the form of seizures, listlessness, irritability and a delay in mental and physical responses. In late-onset and juvenile TSD, the symptoms are less pronounced. These include a slower motor performance or an unsteady gait, slurred speech and hand tremors. In the diagnosis of Tay-Sachs disease, doctors look out for the "cherry-red" spot in the retina that can be detected with an ophthalmoscope.
Effects
Infantile and juvenile Tay-Sachs disease is always fatal and there is no cure. In the later stages, children with the disease are unable to hear, speak and have difficulties swallowing. This eventually leads to paralysis of muscles and death. In late-onset TSD, the disease generally is not fatal but causes muscle twitching and possibly mental illness.
Infants and children with the disease generally live up to five years after the symptoms begin to appear. With adults, the life expectancy is unknown because the disease has only been recently identified as of 2009.
Prevention and Treatment
Because Tay-Sachs disease is genetic, there is currently no treatment for the disease as of 2009. Even with the best of care, children suffering from the disease usually only live until the age of 4. Adult sufferers with late-onset TSD can rely on medication to slow the progress of the disease but cannot reverse its effects. Anti-convulsion medication might help control seizures, and a proper diet can help to keep the airways open and slow the disease.
In terms of prevention, a genetic test can be done on both biological parents to ensure that neither are carriers of the disease.
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