Tuberous sclerosis is a genetic disorder in which noncancerous (benign) tumors grow on the brain, skin, kidneys, eyes, heart, and lungs.
The name tuberous sclerosis refers to characteristics of the benign tumors that grow within the brain. The tumors have root-like or tuberous appendages. Over time, the tumors undergo sclerosis, meaning they calcify and grow hard.
Symptoms of tuberous sclerosis may be identifiable at birth or may develop over time.
In the United States, as of the early 2000s, there are between 25,000 and 40,000 individuals with tuberous sclerosis. Globally, about 1 to 2 million individuals have the disease. The disease occurs in about one out of every 6,000 newborns. There is no gender, racial, or ethnic predilection.
Causes and symptoms
Tuberous sclerosis occurs when at least one of two genes (either TSC-1 on chromosome 9 or TSC-2 on chromosome 16) is defective. Normally, the two genes produce proteins called hamartin and tuberin, respectively. These proteins seem to serve as inhibitors of tumor growth. When the TS genes are defective or absent, the proteins are either absent or deficient, which allows tumor growth.
Most cases of tuberous sclerosis occur due to spontaneous mutations. This means that the disease does not occur due to the inheritance of an abnormal gene, but rather because the baby's gene is defective for some reason other than inheritance.
The tumors of tuberous sclerosis occur throughout the body, including the brain, heart, lungs, kidneys, eyes, and skin. Other symptoms include seizures, developmental delay , behavior problems, and skin problems.
KIDNEYS Cysts on the kidneys tend to appear during the second or third decade of life. In most cases, they do not interfere with kidney functioning. Rarely, there are so many cysts that the kidneys functioning is impaired, or the cysts bleed, resulting in anemia. Fatty growths within the kidneys (called angiolipomas) may grow so large that they cause pain and/or kidney failure. Rarely, malignant tumors of the kidney (renal cell carcinoma) occur within an existing angiolipoma.
BRAIN Several types of brain tumors can grow, resulting in blockage of the flow of cerebrospinal fluid, fluid backup, headaches, and visual disturbances.
HEART Benign tumors in the heart (rhabdomyomas) may block circulation or may exist uneventfully.
EYES White areas in the retina, called phakomas, are characteristic of the disease (and may aid in diagnosis) but do not result in visual disturbances.
SKIN A variety of skin disorders are noted in tuberous sclerosis, including areas of under-pigmented skin (hypomelanic macules); reddish bumps on the face (facial angiofibromas); raised patches on the forehead (called forehead plaques); areas of rough, thickened skin on the neck or back (shagreen patches); tiny fleshy bumps around or under the toe- or fingernails (ungula or subungual fibromas); skin tags (molluscum fibrosum); flat brown patches.
BEHAVIOR About 33 to 50 percent of all tuberous sclerosis patients have problems such as learning disabilities, severe mental retardation , attention deficit disorder, obsessive-compulsive disorder , autism , aggression, rage, or self-harming behavior.
Tuberous sclerosis is diagnosed when the characteristic tumors are noted in the skin, heart, brain, or kidneys. Many patients come to the healthcare provider's attention after they have begun to have seizures. Further examination with CT and/or MRI scans, ultrasound, and Wood's lamps to view the eyes will reveal the presence of the characteristic tumors of tuberous sclerosis.
As of 2004, no cure was available for tuberous sclerosis. Antiseizure medications may be prescribed, as well as medications to treat attention deficit disorder and obsessive-compulsive disorder. Skin lesions may be removed or reduced via dermabrasive or laser procedures. Surgery may be performed to remove enlarging kidney tumors, to avoid the advent of kidney failure.
Most individuals with tuberous sclerosis have a normal lifespan. The prognosis for their quality of life depends on the severity of their behavioral and cognitive symptoms. Individuals whose symptomatology is confined to kidneys or skin (as opposed to having multiple behavioral symptoms) may do very well.
As of 2004, there was no way to prevent tuberous sclerosis.
Parents of child with tuberous sclerosis should be prepared to answer any questions their child or the child's siblings may have about the disease. Siblings may fear they will catch the disease or perhaps caused it, and may need to reassured that they are not at fault.
Haslam, Robert H. A. "Neurocutaneous syndromes." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.
"Neurocutaneous Disorders." In Textbook of Clinical Neurology. Edited by Christopher G. Goetz. Philadelphia: Saunders, 2003.
"Tuberous Sclerosis Fact Sheet." National Institute of Neurological Disorders and Stroke (NINDS). Available online at http://www.ninds.nih.gov/disorders/tuberous_sclerosis.htm (accessed January 9, 2005).
Rosalyn Carson-DeWitt, MD