Tuberous Sclerosis Alliance

How are the TSC genes involved? Tuberous sclerosis complex (TSC) is estimated to occur in one of every 6000 individuals in the population at birth (1). About two thirds of cases are "sporadic", that is "out of the blue", and neither the baby's father nor mother are found themselves to have TSC after full genetic testing. In the remaining one-third of cases, the baby has inherited either the TSC1 or TSC2 gene from their father or mother since anyone with either TSC gene has a 1-in-2 chance of passing it on to any baby they conceive. Recent genetic work has found more inherited cases of tuberous sclerosis linked to a faulty TSC1 gene, and more sporadic cases to a faulty TSC2 gene (2). In addition, the mental retardation and epilepsy associated with growths in the brain, known as cortical tubers, are less frequent in people with TSC1 mutations than in people with TSC2 mutations (3). Parents are often only diagnosed with TSC after their child has been found to have it because they developed an obvious problem, such as infantile spasms, an early form of epilepsy. Their child can go on to develop severe mental retardation and very challenging behaviors, all related to TSC, whereas the parent is not noticeably affected. It is this wide variation in physical and intellectual abilities that is so striking in tuberous sclerosis.