Heredity and Tay Sachs Disease Facts

What is Tay Sachs disease?

Tay Sachs disease is a rare fatal condition that affects the nervous system. One of the unusual Tay Sachs disease facts is that the genetic mutations that cause the disease are more common in people of Northern European Jewish (Ashkenazi) or French Canadian ancestry than those of other backgrounds. People of both sexes are equally affected by the disease.

Cause

The condition is caused by insufficient activity of an enzyme known as beta-hexosaminidase A (Hex-A), which is needed to break down and prevent the build up of fatty substances called gangliosides. In Tay Sachs disease, the fatty substance builds up in the brain and spinal cord causing cell damage and death.

Heredity

A person becomes a carrier of Tay Sachs disease if a properly functioning copy of the Hex-A gene is inherited from one parent and a faulty copy of the gene is inherited from the other. Carriers do not develop the condition. Among Tay Sachs disease facts, it is important to note that in order to develop the condition, both parents must be carriers and the child must inherit the mutated gene from both parents.

Symptoms

Infants afflicted with Tay Sachs disease appear to develop normally at first. Symptoms begin to appear around the age of six months. Symptoms include listlessness, irritability and decreased eye contact. The affected child may stop smiling, rolling over and crawling. He or she will lose the ability to grasp or reach out. Symptoms also include an increased startle reaction to noise, seizures, slow growth and increased head size as well as delayed mental and social skills.

Progression

As the disease progresses, the child may experience difficulty feeding and/or swallowing. There is also a loss of intellectual skill. Vision and hearing loss as well as paralysis may occur. A cherry red spot that develops in the eye is an eye abnormality that is a characteristic symptom of Tay Sachs disease. Most children with Tay Sachs die before the age of five.

Tay Sachs in Adults

Although other forms of Tay Sachs disease are extremely rare, a rare form of the disease can affect adults causing neurological damage and intellectual impairment. The symptoms are generally milder than those seen in infants and may vary widely. Signs include muscle weakness, loss of muscle coordination, mental illness and speech difficulty.

Diagnosis

Diagnosis of Tay Sachs disease can be made by a simple blood test. An enzyme essay measures the level of Hex-A in a person’s blood. Carriers have less Hex-A in their blood than non-carriers. The Hex-A gene was isolated in 1985 and more than 50 mutations have been discovered.

Prognosis

There is no cure for Tay Sachs disease nor is there any form of effective treatment. Research into Tay Sachs disease involves options such as gene transfer that may represent hope for people with this disease.

References

National Institute of Neurological Disorders and Stroke: NINDS Tay Sachs Disease Information Page -

https://www.ninds.nih.gov/disorders/taysachs/taysachs.htm

Disabled World: Defining Tay Sachs Disease -

https://www.disabled-world.com/disability/types/tay-sachs.php

Better Health: Tay Sachs Disease -

https://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Tay-Sachs_disease?OpenDocument