Tuberous Sclerosis Complex (TSC)

What is tuberous sclerosis complex?

Tuberous sclerosis complex (TSC) is a rare genetic condition that causes tumors to grow in many different organs of the body. Tumors grow most often in the brain, skin, heart, eyes, kidneys, and lungs. Almost all of these tumors are benign (not cancerous), but they can cause a variety of health problems.

The symptoms of TSC usually appear before a child is 6 months old. The severity of the condition can vary widely — in some children the disease is very mild, while other children may have life-threatening complications.

What are the symptoms of tuberous sclerosis complex?

The symptoms of tuberous sclerosis complex (TSC) vary greatly from one child to the next, depending on what parts of the body are affected. In some children, the disease involves severe health problems that present early on in life, while other children may have such mild symptoms that they aren’t diagnosed with TSC until much later in life. Each individual will experience symptoms of TSC at different times throughout their life.

Common symptoms may include:

  • Heart tumors. About 50 percent of people with TSC have non-cancerous tumors in the heart, called rhabdomyomas. Most rhabdomyomas do not grow, and either get smaller or stay the same size. In some cases, a baby may be diagnosed with TSC before birth if these heart tumors are found on a fetal echocardiogram. Babies with more than one rhabdomyoma have a higher likelihood of being diagnosed with TSC.
  • Skin lesions. One of the earliest signs of tuberous sclerosis is white skin patches on a baby’s body, called hypomelanotic macules. As the child gets older, he or she may develop other lesions such as a rash across the cheeks and nose, areas of thickened skin, and small bumps under the fingernails or toenails.
  • Brain tumors. Children with TSC may also have one or more types of tumor in the brain. The most common are cortical tubers, subependymal giant cell astrocytomas (SEGAs), and subependymal nodules. Although some children may not have any of these tumors, most children with TSC will have at least one.
  • Seizures. About 85 percent of children with TSC have epilepsy caused by brain tumors. Babies often have a type of seizure called infantile spasms, which involve brief, repetitive muscle contractions and movements in the head, trunk, arms, and legs. These seizures can look like colic or an abdominal problem. Older children and adults may have other types of seizures including generalized, complex partial, and other focal seizures. More than 50 percent of those who have epilepsy have seizures that do not respond to standard medication.
  • Kidney lesions. Over 80 percent of people with TSC have some type of kidney (renal) lesion. The three most common are renal cysts, renal angiomyolipomas, and renal carcinomas. Renal angiomyolipomas are the most common, occurring in more than 80 percent of TSC patients. About 50 percent of people with TSC have renal cysts, which are generally benign, fluid-filled “holes” on the kidney. Cysts can sometimes cause increased blood pressure, and if the kidney becomes filled with cysts, it can cause problems with kidney function. Renal carcinoma, a cancerous growth on the kidney, is the least common type of kidney lesion.
  • Eye lesions. Some children with TSC have lesions on the retina or optic nerve called hamartomas. Most of these lesions stay dormant, and don't usually result in a loss of vision. White patches, or retinal pigmentary disturbances, sometimes appear on the retina, iris, or eyelashes. These white patches aren't harmful and don't require treatment.

What are the causes of tuberous sclerosis complex?

Tuberous sclerosis is an autosomal dominant genetic condition that is caused by a change (pathogenic variant) in either the TSC1 or TSC2 gene. This means:

  • Girls and boys have an equal risk of having the condition.
  • A change in only one copy of a gene causes TSC. A child can inherit the condition if either parent has it.
  • People with tuberous sclerosis have a 50 percent chance of passing the condition to their children.

About one-third of children with TSC inherited the genetic condition from a parent. However, for the other two-thirds of children with TSC, the condition is "spontaneous," meaning that the DNA change is the first instance of that change in the child's family.

Sometimes it is found that a child with TSC has a parent who also has the condition but didn’t know it. If your child is diagnosed with TSC, you may want to have genetic testing done to find out if you have it as well.

If you have one child with TSC, there is an increased chance that your other children will also have the condition.

How we care for tuberous sclerosis complex

At Boston Children’s Hospital, the Multidisciplinary Tuberous Sclerosis Program is a team of pediatric specialists who are dedicated to providing coordinated care for children with TSC. The program is directed by a child neurologist, registered nurse coordinator, and a genetic counselor who are experienced in working with patients and families affected by TSC.

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