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| DiseaseID |
HGD26 |
| Genetic
Disorder |
Tay-Sachs Disease
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| Gene
Name |
HEXA gene |
| Description |
Tay-Sachs disease is a rare inherited disorder that causes progressive destruction of nerve cells in the brain and spinal cord (the central nervous system).
The most common form of Tay-Sachs disease begins in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months, when development slows and muscles used for movement weaken. Affected infants lose motor skills such as turning over, sitting, and crawling. They also develop an exaggerated startle reaction to loud noises. As the disease progresses, children with Tay-Sachs disease experience seizures, vision and hearing loss, mental retardation, and paralysis. An eye abnormality called a cherry-red spot, which can be identified with an eye examination, is characteristic of this disorder. Children with this severe infantile form of Tay-Sachs disease usually survive only into early childhood.
Other forms of Tay-Sachs disease are much rarer. Signs and symptoms can begin in childhood, adolescence, or adulthood and are usually milder than those seen with the infantile form of Tay-Sachs disease. As in the infantile form, mental abilities and coordination are affected. 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 Tay-Sachs disease.
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| Symptoms |
Deafness
Decreased eye contact, blindness
Decreased muscle tone (loss of muscle strength)
Delayed mental and social skills
Dementia
Increased startle reaction
Irritability
Listlessness
Loss of motor skills
Paralysis or loss of muscle function
Seizures
Slow growth
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| Causes |
Tay-Sachs disease occurs when the body lacks hexosaminidase A, a protein that helps break down a chemical found in nerve tissue called gangliosides. Without this protein, gangliosides, particularly ganglioside GM2, build up in cells, especially nerve cells in the brain.
Tay-Sachs disease is due to a defective gene on chromosome 15. When both parents carry the defective Tay-Sachs gene, a child has a 25 percent chance of developing the disease. The child must receive two copies of the defective gene in order to become sick. If only one parent passes the defective gene onto the child, the child is called a carrier.
Anyone can be a carrier of Tay-Sachs. However, the rate of the disease is much higher among the Ashkenazi Jewish population. About 1 in every 27 members of the Ashkenazi Jewish population carry the Tay-Sachs gene.
Tay-Sachs has been classified into infantile, juvenile, and adult forms, depending on the symptoms and when they first appear. Most people with Tay-Sachs have the infantile form. In this form, the nerve damage usually begins while the baby is still in the womb. Symptoms usually appear when the child is 3 - 6 months old. The disease tends to get worse very quickly, and the child usually dies by the age 4 or 5.
Late-onset Tay-Sachs disease, which affects adults, is very rare |
| Diagnosis |
An evaluation begins with a complete physical examination, along with a detailed history of symptoms and family hereditary disorders, including Tay-Sachs disease. A physical exam of the eyes in patients with Tay-Sachs may reveal a "cherry-red" spot in the back of the eyes, a telltale symptom of the disease.
Blood test
A blood test can measure hexosaminidase A (hex A) activity. The biological parents may also have their blood tested to determine if they are genetic carriers of Tay-Sachs. The blood sample may be used for DNA testing to determine genetic mutations that could cause hex A deficiency.
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| Treatment |
Because there is no cure for Tay-Sachs disease, the goal of treatment is to make the patient comfortable. Treatment options include:
Respiratory care
Patients with Tay-Sachs disease frequently will accumulate mucus in their lungs. To reduce the lung mucus, respiratory therapists at Mayo Clinic have extensive experience in providing chest physiotherapy (CPT) and training families to provide CPT to their child when at home.
Children with Tay-Sachs disease are at high risk of respiratory infections, which affect the lungs and cause breathing problems, and need to be carefully monitored and provided with prompt treatment.
Assistive devices
Respiratory problems may also develop when children with Tay-Sachs disease swallow food or liquid into their lungs while eating (aspiration). Assistive feeding devices may be necessary. Two options:
Nasogastric (NG) tube
This is a tube inserted through the nose to the stomach.
Percutaneous Esophago-Gastrostomy (PEG) tube
PEG tubes are placed through the abdomen into the stomach during a surgical procedure that is commonly done by a physician specializing in gastroenterology or radiology. This option is more permanent than the NG tube.
Medication
To reduce the patient's symptoms, a number of prescription medications are available, including seizure medications.
Physical therapy
As Tay-Sachs progresses, the patient may receive physical therapy to stimulate the muscles and joints, such as physically moving the affected body parts.
The purpose of physical therapy is to help keep joints flexible and maintain as much ability to move (range of motion) as possible. This can help to delay joint stiffness, or contractures, and reduce or delay the loss of function or the pain that can result from contractures.
Support for the family
Family members of patients with Tay-Sachs disease need help in coping with the disease and the challenges it represents. Mayo Clinic offers various resources, education and information and will also help family members get connected to local support groups.
Coordination with primary care physician
Mayo Clinic provides treatment and follow-up care for patients with Tay-Sachs disease, and coordinates with the patient's primary care or local physician. |
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