Genetic and metabolic medicine
Noonan syndrome
The commonest RASopathy, its genes and genotype-phenotype links, pulmonary stenosis and HCM, bleeding diathesis before surgery, growth hormone, and how it differs from Turner syndrome.
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Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- The commonest RASopathy, about 1 in 1,000 to 2,500 births. Autosomal dominant in most cases, with many de novo variants.
- Key features: characteristic face, short stature, congenital heart disease (pulmonary stenosis, HCM), bleeding tendency, cryptorchidism and variable learning difficulty.
- Diagnosis is clinical, confirmed by a RASopathy gene panel. A normal result doesn't exclude it, since 10 to 20% have no variant found.
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Sources
- Romano AA, Allanson JE, Dahlgren J et al. Noonan syndrome: clinical features, diagnosis, and management guidelines. Pediatrics 2010;126:746-759American Academy of Pediatrics (Pediatrics), 2010
- Stagi S et al. Multidisciplinary treatment of patients with Noonan syndrome: a consensus statement. JAMA Netw Open 2025JAMA Network Open, 2025
- Kawai M et al. Clinical consensus guidelines for the management of Noonan syndrome in Japan. Clin Pediatr Endocrinol 2026Clinical Pediatric Endocrinology, 2026
- Perrino MR, Das A, Scollon SR et al. Update on pediatric cancer surveillance recommendations for patients with neurofibromatosis type 1, Noonan syndrome, CBL syndrome, Costello syndrome, and related RASopathies. Clin Cancer Res 2024;30:4834-4843AACR Childhood Cancer Predisposition Workshop (Clinical Cancer Research), 2024
- Noonan syndrome (GeneReviews)University of Washington, Seattle (NCBI Bookshelf)
- Noonan syndromeAU/NZhealthdirect Australia
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Turnstile bot check on sign-in and signed-out feedback