Tuberous sclerosis - Causes of tuberous sclerosis

Tuberous sclerosis is caused by a genetic mutation that occurs in one of two genes.

The genes are:

the TSC1 gene
the TSC2 gene

Genetic mutations

Genetic mutations occur when the deoxyribonucleic acid (DNA) inside the gene changes. DNA stores genetic information and this genetic information is altered if the DNA changes, which can cause a genetic disorder.

Mutations are often inherited from a parent, or they can occur when a sperm or egg is made and a new mutation is created. Mutations can also occur if DNA is damaged by natural chemicals, including water and oxygen, or by radiation or sunlight, for example.

Someone with a new mutation will not have a family history of a condition, but they may be at risk of passing on the mutation to their children.

The TSC1 and TSC2 genes

Both of these genes are responsible for regulating cell growth. The genetic mutation is thought to affect the gene's ability to control cell growth properly, leading to multiple tumours throughout the body.

In around a quarter of cases of tuberous sclerosis, a child will inherit one of the mutated genes from one of their parents. If you are a parent who has one of the mutated genes, you have a one in two chance of passing it on every time you conceive a child. The severity of symptoms can often vary between an affected parent and an affected child.

In the other three-quarters of cases of tuberous sclerosis, the mutation occurs for no apparent reason. This is known as a spontaneous mutation. There is currently no way of identifying people who may be more likely to experience a spontaneous mutation.

The chances of getting tuberous sclerosis are the same for both sexes. All ethnic groups are equally affected by the condition.