Tay-Sachs Disease
Description
Tay-Sachs disease is a rare, inherited disorder that primarily affects the nervous system. It is caused by a deficiency of the enzyme hexosaminidase A, which leads to the accumulation of a harmful substance in the brain and spinal cord. This accumulation damages nerve cells, resulting in progressive neurological deterioration. While there is no cure for Tay-Sachs disease, early diagnosis and supportive care can help manage symptoms and improve quality of life for affected individuals.
Genes Involved
Tay-Sachs disease is caused by mutations in the HEXA gene, located on chromosome 15. This gene provides instructions for making the enzyme hexosaminidase A. When the gene is mutated, the enzyme is either not produced or does not function properly.
Recognizing the Signs and Symptoms
Symptoms of Tay-Sachs disease typically appear in infancy and include:
- Delayed development: Slow motor skills, such as sitting, crawling, and walking.
- Muscle weakness and floppy limbs: Difficulty holding the head up or controlling movements.
- Seizures: Sudden, involuntary muscle contractions.
- Cherry-red spot: A red spot on the retina visible during an eye exam.
- Vision loss: Difficulty tracking objects with the eyes.
- Hearing loss: Decreased response to sounds.
- Progressive neurological deterioration: Loss of mental abilities and motor function.
Causes
Tay-Sachs disease is caused by an inherited genetic mutation. Both parents must carry the mutated gene for their child to inherit the disorder. If both parents are carriers, there is a 25% chance their child will inherit the disease, a 50% chance their child will be a carrier, and a 25% chance their child will not inherit the disease.
Inheritance/recurrence risk
Tay-Sachs disease is an autosomal recessive disorder. This means that an individual must inherit two copies of the mutated gene, one from each parent, to have the disease. Carriers of the mutated gene do not have the disease but can pass it on to their children. If two carriers have a child, there is a 25% chance their child will inherit Tay-Sachs disease, a 50% chance their child will be a carrier, and a 25% chance their child will not inherit the disease.
