How is tay sachs inherited

Eye diseases ; Metabolic disorders ; Nervous System Diseases. This disease is grouped under:. Summary Summary. Symptoms Symptoms.

The first symptoms of Tay-Sachs disease may appear from infancy to adulthood, depending on how much beta-hexosaminidase A enzyme activity a person has if any.

In the most common form, the infantile form , infants have no enzyme activity, or an extremely low level less than 0. They typically appear healthy in the newborn period, but develop symptoms within 3 to 6 months of age.

The first symptom may be an exaggerated startle response to noise. Infants with this form begin to lose milestones such as rolling and sitting regression and develop muscle weakness, which gradually leads to paralysis. They also lose mental functions and become increasingly unresponsive to their surroundings. By 12 months of age, they begin to deteriorate more rapidly, developing blindness, seizures that are hard to treat, and difficulty swallowing.

Infants with this form of Tay-Sachs disease typically do not survive past 4 years of age. The most common cause of death is complications from lung inflammation bronchopneumonia. Depending on exactly how much activity there is, symptoms may begin any time during childhood, most commonly between ages 2 and 5.

Children with this form often develop frequent infections, behavioral problems, and have more slowly progressive loss of movement control, speech, and mental function. They may also begin to have seizures and lose their vision. Children with the juvenile form often spend several years having no responsiveness or awareness before passing away in late childhood or adolescence. Infection is a common cause of death. Symptoms and severity vary more among people with this form. Symptoms may begin in childhood to adulthood, but the disease is often not diagnosed until adolescence or adulthood.

Neurological impairment is slowly progressive and may lead to clumsiness and loss of coordination, muscle weakness, tremors , difficulty speaking or swallowing, and uncontrollable muscle spasms and movements. Many people eventually need mobility assistance.

In some people with this form, the first obvious symptom is a severe psychiatric disorder such as schizophrenia. Impaired intellect or dementia may or may not develop.

Some people with the late onset form have a shortened lifespan due to the disease, while others do not. Showing of 32 View All. Loss of developmental milestones. Mental deterioration in childhood.

Hearing defect. Paralysis or weakness of one side of body. Increased reflexes. Fat accumulation in muscle fibers. Fat deposits in muscle fibers.

Lipid accumulation in skeletal muscle. Skeletal muscle lipid accumulation. Mental retardation, progressive. Progressive mental retardation. Increased size of skull. Large head. Large head circumference. Enlarged liver. Low or weak muscle tone. Frequent respiratory infections. Multiple respiratory infections. Susceptibility to respiratory infections.

Involuntary muscle stiffness, contraction, or spasm. Increased spleen size. Lack of feeling, emotion, interest. Dementia, progressive. Progressive dementia.

Decreased muscle tone. Low muscle tone. Onset in first year of life. Onset in infancy. Do you have more information about symptoms of this disease? We want to hear from you. Do you have updated information on this disease? Cause Cause. The HEXA gene provides instructions for making part of an enzyme called beta-hexosaminidase A, which plays a critical role in the brain and spinal cord.

This enzyme is located in lysosomes , which are structures in cells that break down toxic substances and act as recycling centers. Within lysosomes, beta-hexosaminidase A helps break down a fatty substance called GM2 ganglioside. As a result, this substance accumulates to toxic levels, particularly in neurons in the brain and spinal cord.

Progressive damage caused by the buildup of GM2 ganglioside leads to the destruction of these neurons, which causes the signs and symptoms seen in Tay-Sachs disease. Inheritance Inheritance.

Tay-Sachs disease is inherited in an autosomal recessive manner. To find support, talk to anyone on the care team or a hospital social worker. Many resources are available to help your family.

For more information and support, you can also visit:. Reviewed by: Amy W. Anzilotti, MD. Larger text size Large text size Regular text size. What Is Tay-Sachs Disease? What Causes Tay-Sachs Disease? Researchers are studying ways to improve treatment for Tay-Sachs disease.

What Else Should I Know? Tay-Sachs disease. Actions for this page Listen Print. Summary Read the full fact sheet. On this page. What causes Tay-Sachs disease? Tay-Sachs disease TSD is a genetic condition that affects the nervous system. It is caused by an alteration in the HEXA gene on chromosome Males and females are equally affected.

Tay-Sachs disease is a degenerative condition, meaning that symptoms become worse over time. In people with TSD the nerve cells in the brain and spinal cord are progressively destroyed, leading to paralysis.

Symptoms first appear at around six months of age in a previously healthy baby. The life expectancy for children with TSD is around five years of age and there is currently no effective treatment.

The cells of the nervous system neurones , including the brain and spinal cord, need an enzyme called B-Hexosaminidase A HexA to regularly break down a fatty substance called GM2 ganglioside. In children with TSD, the gene that tells the neurones to produce HexA is altered and stops the neurones from producing the enzyme. This means that the fatty substance builds up in the brain and spinal cord, causing cell damage and death.

The genetics of Tay-Sachs disease The genes in our cells are in pairs. This means that: the affected gene is on one of the non-sex chromosomes both copies of the gene need to be altered for a person to have the condition.

If a male and a female, each carrying an altered HEXA gene, conceive a child, there is a: one-in-four chance that the child will have TSD two-in-four chance that the child will be a genetic carrier of TSD one-in-four chance that the child will be completely unaffected by TSD. Symptoms of Tay-Sachs disease The symptoms of TSD in a young baby include: movement problems — loss of ability to smile, reach out, hold onto objects, crawl, turn over or sit up vision and hearing impairment exaggerated reactions to loud noises seizures.

Since a TSD genetic carrier has only one functioning copy of the gene, they will have half the usual amount of HexA in their bloodstream. This is enough for normal brain function.