There are several genetic mutations that cause Noonan syndrome, such as mutations in one of several genes involved in cell signaling and growth, which affect the face, the heart, the growth, and the development of the body. It can be inherited from a parent or occur randomly in a child. Among the physical and health problems associated with Noonan syndrome are distinctive facial features, heart defects, short stature, learning difficulties, and bleeding disorders. Symptoms and complications of Noonan syndrome cannot be cured, but treatments can help manage them.
Causes
The Noonan syndrome is caused by mutations or changes in PTPN11, SOS1, RAF1, RIT1, or KRAS genes. These genes encode proteins that are involved in the signaling pathway that regulates cell growth and division. Approximately half of the cases of Noonan syndrome are inherited from parents with the condition or carries the mutation. Mutations in these genes disrupt the pathway's normal function, leading to abnormal cell growth and development. One copy of the mutated gene needs to be inherited from either parent for the condition to occur. This inheritance pattern is autosomal dominant. The other half of the cases are due to new or de novo mutations in the child's gene during conception or early development. These mutations are not inherited from the parents and do not have family histories of the condition.
Symptoms
Symptoms of Noonan syndrome are highly variable, even within a family. Some people may have mild symptoms, while others may have severe or life-threatening complications. As the person grows and develops, the symptoms may change. Some of the symptoms of Noonan syndrome include:
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People with Noonan syndrome have distinctive facial features, including a large head, a broad forehead, a small lower jaw, a short neck, low-set ears, wide-set eyes, droopy eyelids, a flat nose bridge, a wide mouth, and a high arched palate. As you age, these features may become less noticeable.
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Approximately 80% of people with Noonan syndrome suffer from congenital heart disease, such as pulmonary valve stenosis, atrial septal defect, ventricular septal defect, or hypertrophic cardiomyopathy. Blood flow and oxygen delivery to the body can be affected by these conditions, causing chest pain, shortness of breath, fatigue, or fainting, as well as infections, arrhythmias, or heart failure.
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People with Noonan syndrome often have short stature, which means they are shorter than average for their age and sex. Some males with Noonan syndrome may also have undescended testicles, which can adversely affect fertility and hormone production. They may also have delayed puberty, meaning they begin developing sexual characteristics later than usual.
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Learning problems: People with Noonan syndrome may have mild to moderate intellectual disabilities, which means they have lower than average intelligence and difficulty learning, reasoning, and problem-solving. As well as dyslexia, dyscalculia, and attention deficit hyperactivity disorder (ADHD), they may need special education and support to reach their academic potential.
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There is a possibility that Noonan syndrome patients will develop bleeding disorders, including von Willebrand disease, factor XI deficiency, or platelet dysfunction. Blood clotting can be affected by these conditions, causing excessive bleeding, bruising, and nosebleeds, as well as increased risk of hemorrhage and stroke.
Diagnosis
Genetic testing, clinical features, and family history are used to diagnose Noonan syndrome. The doctor may suspect Noonan syndrome if the person has some of the characteristic facial features, heart problems, growth problems, or bleeding problems. Additionally, doctors may ask about the medical history of the patient and his or her family, and look for signs of inherited or de novo mutations. Noonan syndrome can be diagnosed by genetic testing, which identifies the specific gene mutation causing the condition. Genetic testing can also help determine the risk of passing the condition onto future generations.
Treatment
The symptoms and complications of Noonan syndrome cannot be cured, but treatments can help manage them. Depending on the type and severity of the problems, a team of specialists may be involved, including cardiologists, endocrinologists, geneticists, surgeons, therapists, and educators. Some of the treatment options include:
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Some heart problems, such as arrhythmias, high blood pressure, and heart failure, can be treated with medications. Anticoagulants, clotting factors, and platelet transfusions can also be used to prevent or stop bleeding. Growth hormone, thyroid hormone, or testosterone can also be used to regulate hormone levels.
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It is possible to correct some heart defects with surgery, such as valve repair or replacement, septal closure, or myectomy. Surgery can also fix growth problems, such as orchidopexy, which moves an undescended testicle into the scrotum.
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An individual may benefit from therapy to improve certain learning problems, such as speech therapy, occupational therapy, physical therapy, or behavioral therapy. Therapy can also enhance a person's self-esteem, social skills, and emotional well-being.
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Education: Education can help provide the appropriate learning environment and support for the person, such as special education, individualized education plans, or tutoring. The person's family, friends, teachers, and peers can also benefit from education to increase their awareness and understanding of Noonan syndrome.
Prevention
As Noonan syndrome is caused by genetic mutations either inherited or acquired randomly, it cannot be prevented. However, some of the risk factors and complications can be reduced or prevented.
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In case a person has Noonan syndrome or has a family history of it, genetic counseling can provide them with information and guidance. Inheritance patterns, mutation status, recurrence risk, and reproductive options can be explained by genetic counseling. Prenatal testing and preimplantation genetic diagnosis are also available through genetic counseling, which can detect mutations in fetuses or embryos before conception.
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Eat a balanced diet, exercise regularly, avoid smoking and alcohol, and manage stress to improve one's general health and well-being. It is also possible to prevent or control some of the associated conditions, such as obesity, diabetes, and high blood pressure, through lifestyle changes.
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The symptoms and complications of Noonan syndrome can be monitored and treated with regular check-ups, such as heart problems, growth problems, bleeding problems, or cancer. Anemia, osteoporosis, infections, and other problems can also be detected and treated with regular check-ups.
