Causes

Tuberous sclerosis complex (TSC) is a genetic disease due to a defect or mutation in one of two genes, known as the TSC1 and TSC2 genes. TSC is considered an autosomal dominant disease, which means that a person with TSC has a 50% chance of transmitting the gene to any children.

Sporadic and inherited TSC

Although TSC is a genetic disease, there does not necessarily have to be other family members affected with the disease. Two-thirds of cases of TSC are caused by a sporadic, new mutation, meaning that the affected person is the first one in his/her family to have the gene mutation.

Patients with sporadic TSC have a 50% chance of passing the gene to their children, but other relatives (the patient’s parents, siblings, etc.) are unaffected.

In the other one-third of cases, there is a positive family history of TSC, meaning the disease is inherited. Sometimes mildly affected family members are only found to have the disease after a relative is diagnosed.

TSC gene function

New research shows the TSC genes directly regulate a number of biochemical pathways, such as the mTOR pathway, that control cell growth and proliferation.

Mutation of the TSC genes causes some of these pathways to become abnormally active, resulting in increased cellular growth and proliferation and promoting the tendency to form tumors in different organs.

Although these biochemical mechanisms do not necessarily explain all the symptoms of TSC, these findings have generated much excitement in the field, leading to the development of new drug therapies with mTOR inhibitors for treating tumor growth in TSC.