Frequently Asked Questions about Tuberous Sclerosis

Two genes cause TSC, and only one of the genes needs to be affected for TSC to be present. The TSC1 gene is located on chromosome 9, the same chromosome carrying the gene that determines blood type. The TSC2 gene is located on chromosome 16. TSC occurs when an individual has a mutation in either the TSC1 or TSC2 gene. The mutation can be inherited from one parent or can be a new mutation that develops within the child. 

Recent studies have shown in cases in which two or more people in a family have TSC, about 50 percent have a mutation in TSC1 and the other have a mutation in TSC2. This research also has shown that, in cases in which no prior family history of TSC exists, more individuals have a mutation in TSC2 gene than in the TSC1 gene. 

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TSC is diagnosed by both clinical findings and genetic testing. Some of the tests used to help make the diagnosis are:

• Brain magnetic resonance imaging (MRI) or computed tomography (CT) scan
• Echocardiogram
• Electrocardiogram (EKG)
• Eye exam
• Renal (kidney) ultrasound
• Wood's lamp (ultraviolet light) evaluation of the skin

Genetic testing is available for parents who have TSC and would like to know more about their genetic mutation, or for parents for whom the diagnosis for TSC is questionable. Family members of patients with TSC also may be tested.

TSC affects nearly 50,000 people in the United States and more than one million people worldwide. At least two children born each day will have TSC. Current estimates place TSC-affected births at one in 6,000. 

Many cases of the disorder do undiagnosed due to mild symptoms or lack of familiarity with the disease among physicians and the general public. TSC is as common as amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease), but is still virtually unknown by the general public. 

TSC is either inherited or the result of a spontaneous change in genetic material, called a mutation. Children have a 50 percent chance of inheriting TSC if one of their parents has the condition, but only one-third of TSc cases are known to be inherited. The other two-thirds are believed to be a result of a spontaneous mutation. The cause of the mutations is still unknown. 

People with mild cases of TSC can have a child who is more severely affected. In fact, some people are so mildly affected that they may go undiagnosed until adulthood when their more severely affected child is diagnosed with TSC.

Most people will have a normal life span. There can be complications in organs such as the kidneys and brain that can lead to severe difficulties and even death if left untreated. To reduce these dangers, individuals with TSC should be monitored by their physicians for potential complications throughout their lives.

Tuberous Sclerosis Alliance of Western Pennsylvania
Thistle Elias at 412-624-0097 or elias@pitt.edu

Learn more about Child Neurology.

The tumors resulting from TSC are generally benign, but still may cause problems. Tumors that grow in the brain (SEGAs or subependymal giant cell astocytomas) can block the flow of cerebrospinal fluid in the spaces (ventricles) of the brain. This can lead to behavioral changes, vomiting, headaches, changes in gait, and, if untreated, even death. These tumors often respond to medication, but occasionally require surgical removal. 

In the heart, the tumors are usually at their largest at birth, and then decrease in size as the child gets older. These heart tumors (cardiac rhabdomyomas) can cause problems at birth if they are blocking the flow of blood or causing severe heart rhythm problems. Tumors in the eyes are not common, but can present problems if they grow and block too much of the retina (back of the eye). Tumors in the kidney (renal angiomyolipomas) can become so large that they eventually disrupt the normal kidney functions. In the past, patients were left untreated until they developed kidney failure. Today, doctors are more aggressive and use medication to reduce tumor size, or remove the individual tumors before they get too large and compromise healthy kidney tissue. Individuals with TSC rarely (less than two percent) develop cancerous (malignant) kidney tumors.

Early intervention is helping to diminish the impact of developmental delays on day-to-day functioning, while maximizing a child's ability to reach his or her full potential. Advances in research are resulting in new and improved therapies. Medications such as MTOR Inhibitors (rapamycin, everolimus) have been shown effective in reducing the size and growth of tubers in the brain and kidneys. Surgery to remove tumors is helping to preserve the function of affected organs. Improved technology is helping to pinpoint the regions of the brain responsible for seizures in particular patients, and is creating new therapies to help control or even stop these seizures in those patients.

Tuberous sclerosis complex (TSC) is a genetic condition commonly characterized by seizures and benign tumor in vital organs, such as the brain, heart, kidneys, lungs, eyes, and skin. The disorder affects some children severely, while others are so mildly affected that it may go undiagnosed. 

Some children with TSC experience developmental delays, mental retardation, or autism; however, many people with TSC also live independent, healthy lives and enjoy challenging professions.