Healthy babies develop vision, movement, hearing, and other vital functions in part because enzymes clear out fatty protein and other unwanted material that can interfere with growth. But a baby with Tay-Sachs disease is born without one of those important enzymes, Hexosaminidase A (Hex A). So, as those fatty proteins build up in the brain, they hurt the baby's sight, hearing, movement, and mental development.
A child can only get Tay-Sachs by inheriting it. The genetic trait is relatively common among certain ethnic groups, such as Ashkenazi Jews. Tay-Sachs can be detected before birth, so couples in at-risk ethnic groups who are thinking of having children may want to get a blood test to find out whether their child would be likely to have it.
Signs and SymptomsKids are usually tested for Tay-Sachs after having hearing, sight, and movement problems. A doctor can identify the disease with a physical exam and blood tests.
A baby born with Tay-Sachs develops normally in the first 3 to 6 months of life. During the next months — or even years — the baby will progressively lose the ability to see, hear, and move. A red spot will develop in the back of the child's eyes. The child will stop smiling, crawling, turning over, and reaching out for things. By the age of 2, the child may have seizures and become completely disabled. Death usually occurs by the time the child is 5 years old.
In rare forms of the disease, a child may have the Hex A enzyme, but not enough of it to prevent developmental problems. In one of these forms, called Juvenile Hex A Deficiency, those problems may not appear until the child is 2 to 5 years old. The disease progresses more slowly, but death usually occurs by the time the child is 15 years old.
In another, milder form of Tay-Sachs, the disease causes muscle weakness and slurred speech, but sight, hearing, and mental capabilities remain intact.source
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