NORD gratefully acknowledges Francis J. DiMario Jr., MD, Department of Pediatrics, Neurogenetics-Tuberous Sclerosis Clinic, Connecticut Children's Medical Center, for assistance in the preparation of this report.
Tuberous sclerosis is a highly variable disorder. The signs, symptoms, and severity of the disorder can vary dramatically from person to another, even among members of the same family. This is due, in part, to the specific organ systems that are involved. Any organ system of the body can be affected. Tuberous sclerosis can cause mild disease in which individuals go undiagnosed into adulthood or it can cause significant complications that can impact quality of life or the disorder can cause potentially severe, life-threatening complications.
Because of the highly variable nature of the disorder, it is important to note that affected individuals may not have all of the symptoms discussed below and that the disorder’s expression and progression will be unique in every individual person. Parents should talk to their children’s physician and medical team about their specific case, associated symptoms and overall prognosis.
Nearly all individuals with tuberous sclerosis develop abnormalities of the skin. Many infants have white patches or spots (hypomelanotic macules) on their skin at birth or early during infancy. These abnormal patches of skin can vary in size and shape and sometimes may be quite small and difficult to notice on infants with fair skin. They occur most often on the arms, legs and trunk of the body. The macules may be distinctly white or may appear lighter in color in relation to the surrounding skin.
Small bumps or red spots known as angiofibromas may appear between the ages of 3 and 5 years, primarily on the face and often in a butterfly pattern. The small bumps generally become more numerous and larger as children grow older (until they reach adolescence). Some individuals will develop an irregularly-shaped, thickened, flesh-colored skin rash called a shagreen patch. This rash or plaque of abnormal skin usually develops on the lower back and is sometimes described as having the texture or feel of an orange peel, e.g. rough and dimpled.
Raised, thickened areas of skin called fibrous plaques may develop on the forehead and, less often, the scalp or cheeks. When on the scalp, these lesions may occur with the loss of nearby hair or be surrounded by thick, white hair. Adolescents and adults may develop small benign tumors around or under the nail beds of the fingers or toes (ungual fibroma).
The central nervous system is frequently involved in individuals with tuberous sclerosis. Central nervous system tumors can include subependymal nodules (SENs), cortical dysplasias, and subependymal giant cell astrocytomas or SEGAs. SEGAs occur in approximately 5%-15% of affected individuals and can cause pressure and obstruction within the brain. More than 80% of individuals with tuberous sclerosis have developed early-onset seizures during infancy, most commonly infantile spasms, which are characterized by a sudden jerk followed by stiffening, or focal seizures, in which there is abnormal electrical activity in one specific area of the brain. Most individuals will develop seizures at some point during life and most seizure types have been associated with tuberous sclerosis.
Affected individuals may experience delays in reaching developmental milestones (developmental delays) and have some degree of intellectual disability. Individuals can potentially develop a range of neuropsychiatric disorders including autism spectrum disorder, attention deficit hyperactivity disorder (ADHD), sleep disturbances or disorders, learning and cognitive impairments, or behavioral issues including disruptive and emotional behaviors or problems. The term TSC-associated neuropsychiatric disorders (TANDs) may be used to describe the interrelated, collective behavioral, psychiatric, intellectual, academic, neuropsychological, and psychosocial abnormalities potentially associated with the disorder.
Brain tumors, especially SEGAs, can also cause hydrocephalus by blocking the flow of cerebrospinal fluid (CSF) within the brain. Hydrocephalus is characterized by the accumulation of excess amounts of CSF in and around the brain. The accumulation of CSF within the skull puts abnormal pressure on the brain and can cause a variety of symptoms including headaches, nausea, vomiting, irritability, and behavioral changes.
Another form of tumor associated with tuberous sclerosis is a benign angiomyolipoma. These tumors are made up of fat, blood vessels and smooth muscle cells, usually affect the kidneys, and may not cause any symptoms (asymptomatic). In some instances, they may cause flank pain or kidney (renal) dysfunction. Angiomyolipomas are prone to rupturing and bleeding (hemorrhaging), which can potentially become life-threatening (approximately 20% of the time). Around 70% of affected children may develop a benign angiomyolipoma, usually in later childhood or adolescence. In rare instances, angiomyolipomas or cysts may be found outside of the kidneys such as in the liver. Usually, these growths do not cause any symptoms.
Some women with tuberous sclerosis develop lymphangioleiomyomatosis (LAM), a condition in which the spread and uncontrolled growth (proliferation) of specialized cells (smooth muscle cells) form tumors in the lungs resulting in shortness of breath, coughing, and/or difficulty breathing (dyspnea), especially following periods of exercise or exertion. LAM mostly occurs in women of childbearing age and is extremely rare in men.
Some individuals may develop pulmonary cysts and multifocal micronodular pneumocyte hyperplasia (MMPH), a condition in which multiple nodules form throughout the lungs because of the abnormal proliferation of certain lung cells called pneumocytes. MMPH usually is not associated with any symptoms, but there have been at least two reports in the medical literature of breathing difficulties and eventually respiratory failure associated with MMPH.
In addition to difficulty breathing, the lung complications associated with tuberous sclerosis can cause a collapsed lung (pneumothorax) and chylothorax, a condition in which there is an accumulation of chyle in the space between the membranes (pleura) that line the lungs and chest cavity. Chyle is a milky fluid that consists of lymph and emulsified fats. Chylothorax can cause difficulty breathing, rapid breathing (tachypnea), chest pain, or respiratory compromise.
A benign tumor known as a rhabdomyoma can develop in the heart of infants and young children. The tumor may initially form before birth (antenatally) in the developing fetus. These tumors usually do not cause symptoms and may regress on their own and disappear over time. In some instances, they can interfere or obstruct the flow of blood from the heart (outflow tract obstruction) and/or cause irregular heartbeats (arrhythmias).
Another common finding is the formation of small growths or tumors on the retina, the light-sensitive membrane that coats the inside of the eyes (multiple retinal hamartomas). These tumors rarely cause problems and seldom affect vision.
Some signs and symptoms associated with tuberous sclerosis occur less often than the those described above. These finding are described as minor features of the disorder. Such symptoms include patches or areas of lightened color or a lack of color affecting the retina due to pigment loss (retinal achromatic patch). Some individuals may develop pitting or tiny holes in the enamel of teeth (dental enamel pitting) or the formation of fibrous growths within the mouth (intraoral fibromas), particularly in the gums. In some instances, individuals may develop “confetti” skin lesions during childhood, early adolescence, or adulthood. These lesions are tiny (1-3 millimeters) spots that are lighter in color (hypopigmented) than the surrounding skin. They may be scattered across certain areas of the skin.
Renal cysts, sometimes referred to as epithelial cysts, occur in approximately 20-30% of individuals and usually do not cause symptoms. These small, fluid-filled cysts can, in some instances, result in increased blood pressure. If the kidneys are filled with cysts, kidney dysfunction and kidney failure can eventually develop. Individuals with tuberous sclerosis may have a greater risk of developing certain cancers of the kidney than the general population, although their overall occurrence is still very uncommon. Less than 3% of individuals may eventually develop renal cell carcinoma. In extremely rare instances (less than 1%), an oncocytoma or a malignant angiomyolipoma may occur.
Some affected individuals will develop neuroendocrine tumors (NETs). Neuroendocrine tumors arise from hormone-producing cells of the neuroendocrine system. These cells are a cross or combination of endocrine cells and nerve cells. They are found throughout the body and perform many functions such as regulating air and blood flow through the lungs.
Tuberous sclerosis is caused by an alteration (mutation) in one of two different genes, the TSC1 gene or the TSC2 gene. Genes provide instructions for creating proteins that play a critical role in many functions of the body. When a mutation of a gene occurs, the protein product may be faulty, inefficient, or absent. Depending upon the functions of the particular protein, this can affect many organ systems of the body, including the brain. Generally, alterations in the TSC2 gene result in a more severe disease expression.
In many instances, an alteration causing tuberous sclerosis occurs as a new (sporadic or de novo) mutation, which means that the gene alteration has occurred at the time of the formation of the egg or sperm for that child only, and no other family member will be affected. The disorder is not inherited from or “carried” by a healthy parent. However, such alterations can be passed on through dominant inheritance (where a trait is transmitted from either an affected mother or father to their child).
Most genetic diseases are determined by the status of the two copies of a gene, one received from the father and one from the mother. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary to cause a particular disease. The abnormal gene can be inherited from either parent or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from an affected parent to an offspring is 50% for each pregnancy. The risk is the same for males and females.
The TSC1 gene is located on the long arm (q) of chromosome 9 (9q34); the TSC2 is located on the short arm (p) of chromosome 16 (16p13.3). Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as “p” and a long arm identified by the letter “q.” Chromosome are further subdivided into bands that are numbered.
The TSC1 gene regulates (encodes for) production of a protein known as hamartin that is thought to function as a tumor suppressor. In addition, the TSC2 gene encodes for a different tumor suppressor protein known as tuberin. A tumor suppressor gene is a gene that slows down cell division, repairs damage to the DNA of cells, and/or tells cell when to die, a normal process called apoptosis. Hamartin and tuberin are believed to be inhibit the activity of a chemical pathway in the body called the mammalian target of rapamycin or mTOR pathway. Such a chemical pathway involves a number of complex interactions and is critical for normal human development; the mTOR pathway regulates the creation (synthesis) of proteins that are involved in many cellular functions including cell growth, proliferation, and survival. Alterations in the TSC1 and TSC2 genes ultimately lead to the uncontrolled activity or “hyperactivation” of the mTOR pathway and, consequently, to the development of the tumors that characterize tuberous sclerosis.
Tuberous sclerosis is a rare genetic disorder that affects 1 in 6,000 newborns in the United States. Approximately 40,000 to 80,000 people in the United States have tuberous sclerosis. The prevalence in Europe is estimated to be approximately 1 in 25,000 to 1 in 11,300. As many as 2 million people worldwide are believed to have the disorder. Males and females are affected in equal numbers and the disorder occurs in all races and ethnic groups.
A diagnosis of tuberous sclerosis is based upon identification of characteristic symptoms, a detailed patient and family history, a thorough clinical evaluation, and a variety of specialized tests. For example, the presence of hypopigmented macules on the skin occurring along with seizures or autism are diagnostic clues for tuberous sclerosis. Clinical diagnostic criteria have been established and updated for tuberous sclerosis (Northrup et al. 2013).
Generally, a diagnosis is considered definitive in individuals with two or more major features or one major feature and two or more minor features of the disorder. A possible diagnosis is suspected when one major feature or two or more minor features are present.
In some instances, a cardiac rhabdomyoma can be detected before birth (prenatally).
Clinical Testing and Workup
Molecular genetic testing can confirm a diagnosis of tuberous sclerosis. Molecular genetic testing can detect alterations in one of the two genes known to cause the disorder, and is available as a diagnostic service at specialized laboratories.
A variety of tests can be used to help obtain a diagnosis of tuberous sclerosis or to assess or establish the extent of the disorder in an individual. Such tests include computerized tomography (CT) scanning and magnetic resonance imaging (MRI) to evaluate the brain for the presence of tumors or other brain involvement. An MRI can also be used to evaluate the kidneys or liver for the presence of tumors. A high resolution CT scan can be used to evaluate the lungs. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues.
An echocardiogram and an electrocardiogram (EKG) can be used to evaluate the heart for the presence of a rhabdomyoma. During an echocardiogram, sound waves are directed toward the heart, enabling physicians to study cardiac function and motion. An electrocardiogram records the heart’s electrical impulses and may reveal abnormal electrical patterns.
Treatment may require the coordinated efforts of a team of specialists. Pediatricians and general internists, neurologists, dermatologists, cardiologists, dental specialists, eye specialists, psychiatrists, and other healthcare professionals may need to systematically and comprehensively plan an affect child’s treatment. Genetic counseling will be of benefit for affected individuals and their families.
The treatment for tuberous sclerosis is supportive and symptomatic. Early developmental intervention is important to ensure that affected children reach their potential. Most affected children will benefit from occupational, physical and speech therapy. Various methods of rehabilitative and behavioral therapy may be beneficial. It is essential that therapies are continued on a year-round basis to promote development of new skills and to prevent regression. Additional medical, social and/or vocational services including special remedial education may be necessary. Psychosocial support for the entire family is essential as well.
Anti-seizure drugs (anticonvulsants) may be prescribed to control seizures. The specific drug that is used will depend on several factors including the specific type of seizure, an affected individual’s age, other organ systems that are affected, and the severity of symptoms. Conventional anticonvulsants drugs that may be administered include phenobarbital, phenytoin (Dilantin), clonazepam (Clonopin), valproic acid (Depakene), carbamazepine (Tegretol), ethosuximide (Zarontin), or acetazolemide (Diamox). All these anticonvulsants have potential side effects and require careful monitoring by a physician.
Vigabatrin (Sabril) was approved in 2009 by FDA to treat infantile spasms in children ages 1 month to 2 years. Treatment of children with tuberous sclerosis and infantile spasms with vigabatrin has been found to be effective. Visual field loss is an important safety concern with the use of this medication. The FDA has also approved adreno-corticotrophic hormone or ACTH (Acthar gel) for the treatment of infantile spasms. This medication has also been used to treat infants with tuberous sclerosis. These medications are used cautiously because of their side effects.
No specific anti-seizure medication works for all affected individuals. Often, a combination of different drugs may be required to treat some individuals. Sometimes, seizures can be difficult to treat and medications that initially worked will no longer provide benefit (refractory seizures). In some instances, surgery may be necessary to help to control seizures that don’t respond or stop responding to medications.
Surgery may be necessary if the ability of a particular organ to function properly is impaired by the presence of a tumor. For example, the obstruction of cerebrospinal fluid (CSF) circulation inside the brain (intracranial hypertension) because of a benign tumor may require a shunting procedure to drain the liquid or the surgical removal of the tumor.
In 2012, the U.S. Food and Drug Administration (FDA) approved the use of everolimus (Afinitor) for the treatment of children and adults with tuberous sclerosis who have a subependymal giant cell astrocytoma that cannot be removed or can be only partially removed by surgery.
The FDA also approved everolimus for the treatment of adults with tuberous sclerosis who have an angiomyolipoma of the kidneys that does not require surgery right away. In some instances, angiomyolipomas will require surgery. Large cystic lesions of the kidneys may also require surgical decompression or removal. Cutting off the blood supply (arterial embolization) to a kidney tumor may be used to shrink down the size of the tumor. Embolization is usually followed by treatment with corticosteroids and surgical removal (resection) of the tumor that spares the kidney or by destruction (ablation) of the tumor.
A benign tumor inside the heart (rhabdomyoma) may not cause symptoms and may not require treatment as they often regress on their won. If symptomatic, however, surgical removal (resection) may be necessary. Reports in the medical literature have detailed the off-label use of mTOR inhibitors to treat these tumors with positive results. Some affected individuals may be prescribed certain medications to treat irregular heartbeats (arrhythmias).
Individuals taking mTOR inhibitors for internal tumors (e.g. SEGAs or angiomyolipomas) may see improvement in skin lesions. Topical formulations of mTOR inhibitors have shown promise in treating facial angiofibromas. Individuals with no immediate indication for mTOR inhibitor treatment, may undergo certain procedures to improve the appearance of skin lesions including dermabrasion, laser therapy, or surgical removal (excision) of a lesion.
In May of 2015, the FDA approved the use of mTOR inhibitors for the treatment of lung complications such as LAM in individuals with tuberous sclerosis. Because LAM occurs most often in young women of childbearing age, researchers have speculated that female hormones such as estrogen play a role in the development of the disorder. A link between LAM and female hormones has not been proven. However, many physicians have explored the use of agents that lower the production or effects of estrogen in the body. The results have varied greatly among individuals. Such agents may include medroxyprogesterone acetate. Estrogen-containing medications and dietary supplements should be discontinued in patients with LAM.
Supplemental oxygen therapy may be necessary for some individuals with impaired lung function. In individuals with severe lung disease that is resistant to treatment, a lung transplant may ultimately become necessary.
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