A to Z of syndromes

A-Z Syndromes: Tay-Sachs disease

An insight into this genetic disorder which carries a poor prognosis and is often fatal

An insight into this genetic disorder which carries a poor prognosis and is often fatal

The GM2 ganglioside lipid accumulates abnormally in the infant’s cells and
is toxic to the nerve cells of the brain. Picture: Science Photo Library

Tay-Sachs disease is an autosomal recessive genetic disorder, which results from getting two copies of a defective gene on chromosome 15. Males and females can be carriers and although the disease can affect all races, it was most commonly seen among people of eastern European (Ashkenazi) Jewish descent until a population screening was introduced for Jewish individuals of reproductive age (Kaback and Desnick 2011). Tay-Sachs disease carries a poor prognosis and is often fatal.

Counselling, carrier testing for at-risk family members and the prenatal testing for pregnancies at increased risk can be performed. Carriers are healthy. However, if the two carriers have children together, each pregnancy carries a 25% chance of an affected child and a 50% chance of a child who is a carrier.

The gene affects the way an enzyme called hexosaminidase-A (Hex-A) is produced. The less enzyme that is produced the more severely the child will be affected. Without Hex-A, a fatty substance – or lipid – called GM2 ganglioside accumulates abnormally in the infant’s cells. This is especially toxic to the nerve cells of the brain. The condition is accumulative and progressive.

There are three forms of Tay-Sachs disease, identified by the age of onset:

  • In the most common form, low levels of the enzyme are present and the destructive process can begin in the foetus during pregnancy. Although the infant can at first appear normal, symptoms will appear in the first few months of life. These symptoms include a progressive loss of skills and abilities, the infant will regress, suffer seizures, and lose motor and cognitive capacity. Children with this form do not tend to survive past early childhood.
  • In the juvenile form there is a range of severity, the symptoms can appear at any time during childhood. The symptoms can include behavioural problems, the gradual loss of skills, frequent respiratory infections, and seizures. Children with this form of Tay-Sachs typically do not survive past their teenage years. Some children with the juvenile can spend several years appearing to have limited responsiveness and awareness of their surroundings. Infection is a common cause of death.
  • In late onset Tay-Sachs, the disease is less aggressive and the symptoms do not appear until late childhood or adulthood. The symptoms may be non-specific at first and could include clumsiness, muscle weakness, mental health issues and the gradual loss of motor skills. The individual will need mobility assistance and supported living. The life expectancy will range from being shortened to normal expectancy.

Palliative care

At present there is no cure for Tay-Sachs disease or a treatment to slow its progression. Treatment is supportive and palliative and targeted at managing the symptoms. Decisions need to be made about managing infections; how best to prevent complications; and how to increase the child and family’s quality of life.

Treatment plans could include anticonvulsants to control seizures in children, how best to provide adequate nutrition and maintain good hydration. Immobility can result in severe constipation and fibre additives, stool softeners or laxatives may be required. As the disease progresses, airway management and respiratory support may be offered.

In older children antipsychotic medication may be helpful, but tricyclic antidepressants are not thought to be effective.

Case study

Ryan (not his real name) appeared normal until about six months of age when his development slowed. He and his mother were referred to a large children’s hospital and a diagnosis of Tay-Sachs was confirmed. The family was well supported, with good discharge planning and ongoing communication between the hospital and community teams. The family also made strong links to their nearest children’s hospice for respite and support. The care pathway was agreed between the care teams and the family.

The focus was on palliative management, avoiding hospital admissions and enhancing the quality of Ryan’s life. The care plan was a flexible and responsive document and was continually evaluated. By two years of age, he was experiencing recurrent seizures and diminishing mental function and becoming less responsive to his mother. Further regression over several months meant that he became blind, paralysed and non-responsive.  

With the support of the hospice team an advance care plan was agreed. This specified the treatment in the event of an acute illness and how a sudden deterioration in the child’s condition should be managed.

Reference and link

Further information

Doreen Crawford is nurse adviser with consultancy Crawford McKenzie and consultant editor Nursing Children and Young People

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