Tuberous Sclerosis: A Rare Cause of Benign Tumors

Tuberous sclerosis (also called tuberous sclerosis complex) is a rare genetic disease that causes benign tumors to grow in various organ systems. People with this condition may have tumors in the brain, kidneys, heart, lungs, eyes, liver, pancreas, and skin. These tumors can result in problems like developmental delay, seizures, kidney disease, and more.

Prognosis ultimately depends on the extent of tumor spread. Ultimately, many with the condition go on to live healthy lives.

This article discusses tuberous sclerosis, its causes, and its symptoms. It also looks at some of the treatment options that are available to people with this condition.

Meaning of Tuberous Sclerosis

Tuberous sclerosis is named for the tubers or potato-like tumors that are characteristic of the condition. These growths eventually become calcified and hardened, or sclerotic.

Tuberous sclerosis was discovered more than 100 years ago by French physician Désiré-Magloire Bourneville. At the time it was dubbed Bourneville’s disease and in the 20th century it was also called epiloia.

Prevalence

Tuberous sclerosis is uncommon. It’s estimated that the disease affects around 50,000 Americans and nearly two million people worldwide.

Cause

Tuberous sclerosis is caused by a mutation in one of two different genes. These genes normally instruct your cells to make proteins called hamartin and tuberin. Hamartin and tuberin help make sure your cells grow and divide normally.

In people with tuberous sclerosis, a mutation in one of these genes makes it impossible for cells to make hamartin or tuberin, which leads to cells growing out of control and forming tumors.

Tuberous sclerosis can be inherited in an autosomal dominant fashion. Only one parent needs to have a copy of the mutated gene with autosomal dominant diseases to pass the illness down to a child.

More commonly, tuberous sclerosis happens because of a spontaneous mutation. Neither parent carries the gene mutation responsible for the condition in these cases.

One of the two genes responsible for tuberous sclerosis is located next to the gene that causes autosomal dominant polycystic kidney disease (ADPKD). ADPKD is a similar condition that causes tumors to grow in the kidneys. This increases the likelihood of a mutation in both genes, which is why some people with tuberous sclerosis also have ADPKD.

Symptoms

People with tuberous sclerosis have symptoms involving various organ systems.

Brain Involvement

Tuberous sclerosis causes three types of tumors in the brain:

• Cortical tubers: These typically occur on the surface of the brain but can develop deeper in the brain.
• Subependymal nodules: These occur in the ventricles, large structures inside your brain that are filled with fluid. 
• Subependymal giant-cell astrocytomas: These tumors block the flow of fluid in the brain, resulting in a build-up of pressure that can cause headaches and blurred vision.

Brain tumors are typically the most damaging consequence of this disease. Seizures and developmental delays are common among those with this illness.

Kidney Involvement

People with tuberous sclerosis can have kidney tumors called angiomyolipomas. These tumors typically occur in both kidneys and are usually benign, which means they don’t spread to other parts of the body. If they grow to more than 4 centimeters (cm) in diameter, however, they can bleed and will need to be surgically removed.

Very rarely does tuberous sclerosis result in chronic kidney disease and kidney failure.

Tuberous sclerosis can increase the risk of renal cell carcinoma (kidney cancer). This is why people with tuberous sclerosis should be regularly screened for this type of cancer.

Skin Involvement

Nearly all people with tuberous sclerosis have skin lesions. These include the following:

• Hypomelanotic macules (“ash-leaf spots” which are patches on the skin that lack pigment and thus are lighter than surrounding skin)
• Shagreen patch (focal leathery thickening of the skin)
•  “Confetti” lesions
• Fibrous facial plaque
• Facial angiofibromas
• Ungual or subungual fibromas (growing around or under the nails)

These skin lesions are benign, but they can result in disfigurement. This is why many people choose to have them surgically removed.

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Heart Involvement

Infants born with tuberous sclerosis often have heart tumors called rhabdomyomas. In most infants, these tumors don’t cause problems and shrink with age. If the tumors get big enough, however, they can block circulation.

Treatment

There is no specific cure for tuberous sclerosis. Instead, healthcare providers focus on treating the symptoms of the disease. For example, antiepileptic medications can be given to treat seizures. Surgery can also be performed to remove tumors from the skin, brain, etc.

In 2022, the Food and Drug Administration (FDA) approved Hyftor (sirolimus topical gel) for the treatment of facial angiofibroma in patients 6 years and older with tuberous sclerosis complex. New medicines like Afinitor (everolimus) may also help people with this condition.

Summary

Tuberous sclerosis is an uncommon genetic disease that causes benign tumors to grow in certain parts of the body. In some people, the condition can cause lifelong problems like seizures and kidney disease. In others, the disease causes fewer problems.

Tuberous sclerosis is most dangerous when it causes tumors in the brain. Many people with the condition also have skin lesions, which don’t tend to be dangerous but can be disfiguring. These lesions can usually be removed surgically.

A Word From Verywell

If you or a loved one has been diagnosed with tuberous sclerosis, please know that the prognosis or long-term outlook for this condition is highly variable. Some infants with this condition face lifelong seizures and severe intellectual developmental disorder, but others go on to live otherwise healthy lives.

Prognosis ultimately depends on the extent of tumor spread. Nevertheless, people with this condition should be closely monitored since there is always the possibility a brain or kidney tumor could become serious and life-threatening.