Tay-Sachs disease - Symptoms of Tay-Sachs disease

In the most common form of Tay-Sachs disease, classic infantile Tay-Sachs disease, a baby will develop normally until they are around three to six months old.

One of the first noticeable signs of the condition is the appearance of a red dot at the back of their eyes. You may also notice that their vision seems poor or that they are excessively startled by noises and movement.

It is likely that your baby will be much slower in reaching developmental milestones, such as learning to crawl.

Additional symptoms usually develop after about eight months of age and quickly become more severe. They include:

• increasing muscle weakness that progresses to paralysis (inability to move body parts)
• increasing loss of vision
• loss of hearing 
• difficulties swallowing (dysphagia)
• muscle stiffness (spasticity)
• lack of interest in the world around them
• repeated fits (seizures)

Due to the increasing damage to the nervous system, children with Tay-Sachs disease become increasingly vulnerable to infection, particularly lung infections. Many children with the condition die from a complication of an infection such as pneumonia.

Most children with infantile onset Tay-Sachs disease die at around four years old because of complications from repeated infections.

Rarer forms of Tay-Sachs disease

There are two much rarer forms of Tay-Sachs disease, which are described below.

Juvenile form

In the juvenile form, the symptoms do not usually begin until a child is 2 to 10 years old.

Initially, the child will have problems with speech and motor skills, such as balance, walking and holding objects. Some children may also develop problems with vision.

As the condition progresses, the child will have repeated fits and experience an increasing loss of mental abilities such as memory, thinking and understanding. This is known as dementia. Dementia is usually associated with ageing but it can affect people of all ages, although it is rare in children.

Children with the juvenile form of Tay-Sachs disease will usually die in the second or third decades of life due to a complication of an infection.

Late-onset form

The symptoms of late-onset Tay-Sachs disease develop later in life, usually during the teenage years or even early adulthood.

Symptoms include:

• slurred speech
• loss of balance and co-ordination
• uncontrollable shaking of the hands (tremor)
• muscle cramps and twitching
• muscle weakness

Around one in three people with late-onset Tay-Sachs disease will also develop psychosis. Psychosis is a mental health condition where a person is unable to tell the difference between the real world and their imagination. They may see or hear things that aren't there (hallucinations) or believe things that aren't true (delusions).

Unlike other forms of the condition, late-onset Tay-Sachs disease doesn't always shorten life expectancy.