What is TS?
History
The Genes that cause TS
Clinical Manifestations

There are two genes that can cause tuberous sclerosis, but only one defective gene is needed to have the disease. The exact location of the TSC1 gene, which is on chromosome 9, is still unkown, but researchers predict that it will be discovered within the year. The TSC2 gene on chromosome 16 was located at the end of 1993.

While there is no obvious difference in the clinical features caused by the TSC1 and TSC2 genes, finding the TSC1 gene will lead to genetic tests for TS. Futher studies on the two TS genes will shed light on how gene mutations occur and could lead to lead to new treatments for individuals with this disease.

The reason for the extreme variability of manifestations of TS in individuals is unknown, but some geneticists hypothesize that "modifying genes," which determine the level of clinical expression in affected individuals, exist along with the TS genes. Others speculate that different mutations in the TS genes lead to various signs of TS. Ongoing genetic research will detemine the cause. (For more detail, check out Q&A: Genetics of TS.)

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