Tuberous sclerosis
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Tuberous sclerosis
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Which of the following additional findings is most likely to be found on further examination of this patient?
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Autosomal dominant disease
tuberous sclerosis p. 539
Hamartomas p. 223
tuberous sclerosis p. 539
Mitral regurgitation
tuberous sclerosis p. 539
Rhabdomyomas p. 320
tuberous sclerosis p. 539
Seizures p. 531
tuberous sclerosis p. 539
Tuberous sclerosis p. 539
tumor suppressor genes and p. 220
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Tuberous sclerosis is a genetic condition that causes growths to form in various body organs. Most commonly affecting the brain, skin, kidneys, lungs, and eyes.
Normally, there are two genes called TSC1 and TSC2 that help control the growth and division of cells in the body.
TSC1 encodes the protein hamartin and TSC2 encodes the protein tuberin.
Both of these proteins, are tumor suppressors, meaning they help slow down cell growth and prevent tumors.
They do this by combining to form a hamartin-tuberin protein complex, which binds to and inhibits another protein called mechanistic target of rapamycin, or mTOR.
mTOR activity speeds up the cell cycle and increases cell proliferation mainly thanks to its effect on protein synthesis.
So when mTOR is switched off by the hamartin-tuberin protein complex, it slows growth and division of cells throughout the body.
Individuals with tuberous sclerosis have a mutation in either the gene TSC1 or TSC2, and these mutations have an autosomal dominant inheritance pattern.
The mutations lead to an altered hamartin-tuberin protein complex that’s unable to switch off mTOR.
Because of that, benign tumors and growths called hamartomas form throughout the body.
Hamartomas are kind of like tumors, but they’re made of a variety of cell types from the tissue where they arise, rather than a single cell type.
In fact, if we think of the tissue like a sheet of fabric, a hamartoma is like a knot in the sheet.
Benign tumors and hamartomas can form in any tissue, but the brain and the skin are usually affected the most, along with the kidneys, lungs and eyes.
On top of that the lifetime risk of cancer is increased in individuals with tuberous sclerosis.
That’s because the rapidly dividing cells can develop additional mutations that eventually make these growths expand beyond the basement membrane and invade neighboring tissues.
In the brain, the most common growths are glioneural hamartomas, also known as a cortical tubers. They arise from supportive glial cells as well as neurons.
Next most common are subependymal nodules, which are hamartomas that form under the ependyma, the thin membrane that lines the ventricles in the brain.
Individuals are also at an increased risk of developing a subependymal giant cell astrocytoma, or SEGA, which is a type of cancer that can arise from the subependymal nodules.
Summary
Tuberous sclerosis, also known as tuberous sclerosis complex (TSC), is a rare genetic disorder that causes noncancerous tumors to grow in various parts of the body. The condition is caused by mutations in one of two genes, TSC1 or TSC2, which are responsible for regulating cell growth and division.
TSC can affect multiple organs, including the brain, skin, kidneys, heart, and lungs. Symptoms vary widely depending on the location and size of the tumors but may include seizures, intellectual disability, developmental delays, skin lesions, kidney problems, and lung complications.
Diagnosis of TSC typically involves a combination of clinical evaluation, imaging studies, and genetic testing. Treatment may involve a variety of interventions depending on the specific symptoms and organ involvement, such as antiepileptic medications for seizures, surgical removal of tumors, or targeted therapies to block cell growth in affected organs.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "A clinical update on tuberous sclerosis complex‐associated neuropsychiatric disorders (TAND)" American Journal of Medical Genetics Part C: Seminars in Medical Genetics (2018)
- "Renal manifestations of tuberous sclerosis complex: Incidence, prognosis, and predictive factors" Kidney International (2006)
- "Abnormal glycogen storage in tuberous sclerosis complex caused by impairment of mTORC1-dependent and -independent signaling pathways" Proceedings of the National Academy of Sciences (2019)
- "Tuberous Sclerosis Complex Diagnostic Criteria Update: Recommendations of the 2012 International Tuberous Sclerosis Complex Consensus Conference" Pediatric Neurology (2013)