Tay-Sachs disease is a fatal inherited disease of the central nervous system as a recessive gene. The central nervous system includes the brain, the coverings of the brain, and the spinal cord. The most common form of the disease affects babies. Babies with Tay-Sachs disease lack hexosaminidase A, an enzyme that is necessary for breaking down certain fatty substances in brain and nerve cells. These fatty acids then accumulate in the brain causing neurological deterioration. Affected babies appear healthy at birth and seem to develop normally for the first few months of life. The destructive process begins in the fetus early in pregnancy.

Symptoms of classical Tay-Sachs disease first appear at 4 to 6 months of age when an apparently healthy baby gradually stops smiling, crawling or turning over, loses its ability to grasp or reach out

There is no cure and no treatment that will prevent the disease from running its course. Affected children can only be made as comfortable as possible. Only supportive treatment is available. However, there is active research being done in many investigative laboratories in the U.S. and around the world. The use of enzyme replacement therapy to provide the Hex-A, which is missing in babies with Tay-Sachs disease, has been explored. Although this approach is good, scientists still face serious obstacles. Because the disease affects brain cells, which are protected by the blood-brain barrier, enzymes like Hex-A are blocked from entering the brain from the blood. Bone marrow transplantation has also been attempted, but has not been successful in reversing or slowing damage to the central nervous system in babies with Tay-Sachs disease.

The classic infant type of Tay-Sachs disease is the most common. However, there are other rare types of the Hex-A enzyme that sometimes are included under the name of Tay-Sachs disease. These often are referred to as juvenile, chronic and adult-onset forms of Hex-A deficiency. Affected individuals have low levels of the Hex-A enzyme that is missing entirely in the classical infant form. This explains why symptoms begin later in life and are milder than in the classical infant Tay-Sachs disease. Children with juvenile Hex-A deficiency develop symptoms between the ages of 2 and 5 that resemble those of the classical infant form. The process of the disease is slower, but death still occurs by age 15. Symptoms of chronic Hex-A deficiency also may begin by age 5, but are milder than those that characterize the infant and juvenile forms. Mental abilities, vision and hearing remain intact, but there may be slurred speech, muscle weakness, muscle cramps, tremors, unsteady gait and, sometimes, mental illness. Individuals with adult-onset Hex-A deficiency experience many of the same symptoms as individuals with the chronic form, but the symptoms begin later in life.

Although a cure for Tay-Sachs disease does not exist at the present time, support for families of affected children is available through organizations such as the National Tay-Sachs and Allied Diseases Association. Time in an extended-care facility for basic care if parents

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