The MYH11 gene provides instructions for creating a protein called smooth muscle myosin heavy chain (SM-MHC), which is essential for the proper function of smooth muscle cells. Smooth muscle cells are found in various organs throughout the body and are responsible for involuntary movements like the contraction and relaxation of blood vessels, the digestive tract, and the respiratory system.
Mutations in the MYH11 gene can lead to various health conditions, including hereditary thoracic aortic aneurysm and dissection (HTAAD), a potentially life-threatening cardiovascular disorder.
HTAAD is characterized by a weakening of the aortic wall that can result in an abnormal dilation of the aorta, the main artery that transports oxygenated blood from the heart to the rest of the body. The weakened aorta can eventually rupture or tear, leading to severe bleeding and possible death.
MYH11 gene mutations are inherited in an autosomal dominant manner, which means that a person only needs to inherit one copy of the faulty gene from one parent to develop the disorder. Each child of an affected individual has a 50% chance of inheriting the mutated gene.
HTAAD is a relatively rare condition, affecting about 1 in 5,000 individuals. However, it can be life-threatening if not detected early and treated promptly.
Symptoms of HTAAD may include chest pain, back pain, shortness of breath, hoarseness, coughing, difficulty swallowing, and loss of consciousness. However, some individuals may not experience any symptoms until a rupture or tear of the aorta occurs.
Diagnosis of HTAAD usually involves a physical exam, a review of medical history, imaging tests like echocardiography or computed tomography (CT) scans, and genetic testing to confirm the presence of MYH11 gene mutations.
Treatment of HTAAD depends on the severity of the condition and may include medication to lower blood pressure, surgical repair of the aorta, or a procedure called endovascular stent grafting that involves inserting a mesh-like tube called a stent into the weakened area of the aorta to strengthen it.
Preventative measures for HTAAD include regular monitoring of aortic size and blood pressure, adopting a healthy diet and exercise routine, avoiding smoking and excessive alcohol consumption, and genetic counseling for individuals with a family history of the condition.
MYH11 gene mutations can also cause other disorders, like hereditary nonpolyposis colorectal cancer (HNPCC), a genetic condition that increases the risk of developing colon, rectal, and other types of cancer.
HNPCC is caused by mutations in several different genes, including MYH11, that regulate the repair of DNA damage. Individuals with an inherited mutation in one of these genes have approximately an 80% chance of developing colon or rectal cancer during their lifetime, compared to a normal risk of less than 5%.
Symptoms of colon or rectal cancer can include changes in bowel habits, abdominal pain, blood in the stool, unexplained weight loss, and fatigue. However, early-stage colon or rectal cancer may not cause any symptoms, highlighting the importance of regular colorectal cancer screening for all individuals over the age of 50, or earlier for those with a family history of the disease.
Colorectal cancer screening methods include stool tests, flexible sigmoidoscopy, colonoscopy, and CT colonography. Treatment options for colorectal cancer depend on the stage and location of the cancer and may include surgery, radiation therapy, chemotherapy, or a combination of these treatments.
MYH11 gene mutations can also lead to other conditions, like familial thoracic aortic aneurysms with dissections (FTAAD), aortic valve disease, and smooth muscle tumors.
Research is ongoing to better understand the role of MYH11 gene mutations in these and other disorders and to develop more effective treatments and preventative measures.
In summary, MYH11 gene mutations are associated with various health conditions, including hereditary thoracic aortic aneurysm and dissection, hereditary nonpolyposis colorectal cancer, familial thoracic aortic aneurysms with dissections, aortic valve disease, and smooth muscle tumors.
Early detection and treatment of these conditions are essential for optimal outcomes. It is recommended that individuals with a family history of these disorders or with suspected symptoms undergo genetic testing and seek appropriate medical care.
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Genetic counseling is also recommended to provide individuals and their families with information about the inheritance pattern and the risks and benefits of testing and treatment options. Research is ongoing to better understand the role of MYH11 gene mutations in these conditions and to develop more effective treatments and preventative measures.