TSC2 and tuberous sclerosis: It is commonly estimated that TSC is a rare condition with an average frequency of 1:6000 live births, and the prevalence ranges between 1:14,000 and 1:25,000 [189,191], and mutations in one of the two tumor suppressor genes, TSC1 (encoding hamartin) or TSC2 (encoding tuberin) occurs in more than 85% of TSC cases [192].