Tay-Sachs disease is a rare disorder characterised by a deficiency in an enzyme that results in a build-up of fats in the brain and nerve cells. Because of this, Tay-Sachs disease can be described as a neurodegenerative disorder. Progressive build-up of these fats eventually leads to the malfunction of the central nervous system.
Tay-Sachs disease is considered to be a lysosomal storage disease. These are digestive units in cells, and enzymes within lysosomes help break down nutrients. If certain enzymes are missing or deficient, then major health problems occur.
The most common form of Tay-Sachs disease is the infantile form, and this can present itself within the first six months of life. There is also a juvenile form that begins from around the age of two onwards. Late-onset Tay-Sachs disease starts in the mid to late teens onwards. All forms are inherited from parents carrying the faulty gene.
Once symptoms develop in infants, they progress quickly. Early signs and symptoms can include twitching and spasming of the muscles and sensitivity to sounds.
Beyond six months of age, infants can fail to thrive and develop normally. Motor skills are often affected too, and unusual eye movements may occur. Youngsters with this disease may be irritable and display slow growth.
Gradual loss of vision, involuntary muscle spasms, and loss of any acquired skills, such as crawling, may follow. A cherry-red spot may also be present at the centre of the macula.
Further advances in symptoms often include seizures, loss of sight, hearing loss, feeding and swallowing difficulties, and eventual paralysis. If an infant lives beyond the age of three, then life-threatening symptoms appear, such as aspiration pneumonia which can lead to eventual respiratory failure and death.
Those with juvenile-onset Tay-Sachs disease can develop symptoms between the ages of two and ten years of age. An early sign of the developing disease in those with this form is a deterioration in coordination.
Further progression can affect speech and intellect. Visual problems due to the degeneration of the optic nerve also follow. Eventually, by the early to mid-teens, life-threatening complications can become a possibility, along with the development of swallowing difficulties, poor balance, and psychiatric disorders.
Late-onset Tay-Sachs disease symptoms usually start to show in the late teens or at any point in adulthood. Muscle weakness and muscle wasting are early symptoms, along with poor coordination, muscle cramps, and spasms.
Tay-Sachs disease is caused by a mutation in the hexosaminidase subunit alpha gene. This is involved in the production of the enzyme hexosaminidase A. Insufficient amounts in the body allow fats called gangliosides to build and accumulate in the brain and nerve cells, resulting in the development of numerous symptoms.
Risk factors are carriers of the genes having children and passing the mutated genes to their infants. Tay-Sachs disease is inherited as an autosomal recessive disease, meaning that two copies of the faulty gene, one from each parent, are needed to place an infant at high risk of developing this disorder.
Blood tests and other lab investigations are used if Tay-Sachs disease is suspected. These investigations can measure the levels of enzymes and fats in the body.
There is no approved treatment for this disease. Therefore, the focus is on symptom management. This can involve paediatricians, audiologists, neurologists, and speech therapists.
Drugs such as anticonvulsants may be used if seizures are present, and the use of a feeding tube may be needed if swallowing becomes problematic. Clinical trials in enzyme replacement therapy are ongoing.
Prevention of the disease requires potential parents to take part in genetic screening for the gene mutation.