Noonan syndrome is caused by a congenital abnormality of a gene related to the intracellular Ras/MAPK signal transduction system, which is characterized by facial features, congenital heart disease, cardiomyopathy, short stature, thoracic abnormality, retention testis, and mild intellectual disabilities. It is an autosomal dominant hereditary disease that shows genetic disorders. (1)
Is Noonan Syndrome A Disability?
Noonan syndrome involves problems in multiple body areas of the patient that may lead to certain disabilities to several individuals. However, these disabilities are often not severe and vary considerably from patient to patient. Usually, there is no marked physical disability, but children with Noonan Syndrome may suffer from an IQ level lower than average (marginally). For most individuals with Noonan syndrome, intelligence is not compromised. For those with learning disabilities, symptoms such as moderate cognitive, intellectual, and learning problems may appear. Various behavioral, emotional, and mental issues are common with some vision and hearing deficits. All of these symptoms are mild. (2)
Characteristic facial symptoms in Noonan syndrome include problems with eye-opening, eyelid cleft, eyelid drooping, congenital heart disease, cardiomyopathy, short stature, thoracic abnormality, retention testis, intellectual disability, etc. Sometimes the symptoms are associated with leukemia or solid tumors.
Congenital heart disease is one of the defining life prognoses in Noonan syndrome and is an important issue seen in many patients. Typically, pulmonary valve stenosis is found in more than half of patients where blood flow to the lungs can be affected, leading to cyanosis.
Additionally, the burden on the right ventricle is increased, and symptoms of right heart failure (shortness of breath, pleural effusion, ascites, etc.) may occur. The next most common is hypertrophic cardiomyopathy, which can lead to chest pain, fainting, and sometimes sudden death.
Many patients also suffer from short stature, funnel chest, deafness, valgus elbow (unable to straighten the hands), a short neck, spine deformities, abnormal cough, etc.
The disorder may be accompanied by abnormalities in the blood system and may make blood clotting difficulties. Acute leukemia, the formation of cancerous tumors are sometimes seen in a few patients. (3)
Development And Learning Issues In Noonan Syndrome
Motor development in childhood is often delayed. There are many patients who do not have any problems with intellectual aspects, but they may present learning disabilities. There may be abnormalities in hearing and vision, which may affect the learning side. Other organ features may also get affected by this disorder along with infertility. (2) (3)
The gene responsible for Noonan syndrome-related diseases is a molecule involved in the RAS/MAPK signaling pathway by BRAF, CBL, KRAS, NRAS, PTPN11, RAF1, RIT1, SHOC2, and SOS1. These are genes for congenital abnormalities. However, about 40% of patients do not have mutations in these genes and are believed to have novel etiologic genes. (1)
Diagnosis Of Noonan Syndrome
The diagnosis of Noonan syndrome is mainly based on the characteristics of various organs in the body. In addition, genetic diagnosis targeting the causative gene may be performed. However, it is not uncommon that genetic abnormalities cannot be identified. As the final diagnosis may have important clinical symptoms, it is important to see a doctor who specializes in treating Noonan syndrome.
Various tests are performed to evaluate different complications. Specifically, the function of the heart may be evaluated by echocardiography or X-rays, or a blood test may be performed to check for blood system abnormalities. Other tests may also be performed to distinguish them from other diseases that have similar symptoms. Specifically, a chromosome test is used to differentiate from Turner syndrome, which is also associated with short stature. (4)
Treatment For Noonan Syndrome
- Totoiu MO. Developmental and Neurological Features of Noonan Syndrome. Noonan Syndrome: Elsevier; 2019:93-111.
- Roberts AE, Allanson JE, Tartaglia M, Gelb BD. Noonan syndrome. The Lancet. 2013;381(9863):333-342.
- Noonan JA. Noonan syndrome. Health Care for People with Intellectual and Developmental Disabilities across the Lifespan: Springer; 2016:827-832.
- Romano AA, Allanson JE, Dahlgren J, et al. Noonan syndrome: clinical features, diagnosis, and management guidelines. Pediatrics. 2010;126(4):746-759.
- Hemmati P, Dearani JA, Daly RC, et al. Early outcomes of cardiac surgery in patients with noonan syndrome. Paper presented at: Seminars in thoracic and cardiovascular surgery2019.
- Osio D, Dahlgren J, Wikland KA, Westphal O. Improved final height with long‐term growth hormone treatment in Noonan syndrome. Acta Paediatrica. 2005;94(9):1232-1237.
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