Incurable but treatment available
Tuberous sclerosis is a rare, genetic disease that causes non-cancerous tumours to grow in the brain and other vital organs.
There is no cure but medication and treatment can help to reduce the severity of symptoms.
Common symptoms include seizures, behavioural problems, learning disabilities, kidney and skin problems.
The disease occurs in one in every 6,000 births in the United States.
The most common cause of death in tuberous sclerosis patients is a prolonged seizure. The brain surgery needed to remove the tumours is very difficult because neurosurgeons must identify which area of the brain is causing the seizures.
A Health Department spokesman said 78 people in Hong Kong had been diagnosed with the disease since 1991, and the age of onset and diagnosis ranged from early childhood to adulthood.