Late-onset Tay-Sachs (LOTS) is a very rare genetic disease in which fatty compounds, called gangliosides, do not break down fully because the body produces too little of the enzyme hexosaminidase A (Hex A). Over time, gangliosides build up in the brain and damage brain nerve cells. This affects a person's mental functioning.

This condition occurs most often in people of Ashkenazi Jewish descent. People who have family from the Quebec Bas-St-Laurent or Gaspésie regions or New Brunswick territories are also at a higher risk than the general population.

Symptoms of LOTS vary but usually include clumsiness or mood changes that begin between adolescence and the mid-30s. At first, symptoms are subtle and may go unnoticed. Other symptoms that may occur include:

• Personality changes.
• Muscle weakness or twitching.
• Slurred speech.
• Impaired thinking and reasoning ability, such as memory problems, difficulty with comprehension, and short attention span.
• Inability to distinguish between what is real and unreal (psychotic episodes) or depression.

Treatment for late-onset Tay-Sachs disease focuses on controlling symptoms. There is no cure. The life expectancy for a person with LOTS is unknown. Depending on the severity of the symptoms, the person may live as long as someone who does not have the disease.