Tuberous sclerosis (also known as TSC) is a genetic disease that affects 1 in 6,000 births. Although it is a genetic disorder, most cases are not inherited (sporadic), between 66-85% of people with this condition are born to healthy parents who are not carriers of the gene mutation that causes this disease.
TSC is a multi-system disease that can result in a variety of symptoms, which this article will discuss.
What are the symptoms?
- Epileptic seizures – seizures occur in 80-95% of patients. In most people with TSC, seizures appear before one year of age and are mostly the only sign for the disease. In some cases, seizures can occur on only one side of the body or in one limb but may include all organs and in severe cases include altered awareness, sudden laughter, staring into space, and more.
- Cognitive impairments – 50% of patients have intellectual disability, 15% have autism, and 43-51% have various psychiatric and behavioral disabilities.
- Skin abnormalities – 90% of patients suffer from white patches on the skin that appear during childhood, 80% suffer from a distinctive facial rash.
- Eye abnormalities – 40-50% of people with TSC develop retinal lesions (or hamartomas), these are usually noncancerous and do not cause vision impairments.
- Heart impairments – 70-80% of patients suffer from heart tumors (known as cardiac rhabdomyomas) that usually regress over time and do not cause heart dysfunction. In a small number of cases these tumors cause cardiac rhythm disturbances (arrythmia) or other heart impairments.
- Other organ systems – in most patients, symptoms affect other organs such as the liver, lungs, and kidneys. However, in most cases these symptoms include noncancerous tumors or cysts that are rarely a cause for concern.
Mutations in the TSC1 gene (located on chromosome 9), or in the TSC2 gene (located on chromosome 16), can cause tuberous sclerosis.
Most patients do not inherit the disease from their parents. This occurs when parents did not develop the disease but are carriers of the relevant gene mutation in their germ cells.
Can genetic testing detect this disease?
Since TSC is caused by mutations to one in two possible genes and by a wide variety of possible mutations, carrier diagnosis of this disease may prove difficult. Moreover, the two relevant genes are very large, which causes their sequencing to be time consuming and expensive.
However, in familial (inherited) TSC, genetic screening can be performed to known genes. This test is usually possible when at least five family members have the disease.
Can the disease be diagnosed prenatally?
This disease cannot be diagnosed prenatally, unless heart tumors are present which can be detected during fetal echocardiography.
How is the disease diagnosed in adults?
A TSC diagnosis in adults is achieved by detecting two major features or one major feature and two minor features. Major features include, for example, white patches on the skin and facial rash, while minor features include renal cysts, cysts in the bones, and more.