Noonan syndrome

Overview

Board takeaway: Address cardiac disease and bleeding risk separately before invasive care; normal screening coagulation tests do not exclude every bleeding disorder.

Pulmonary valve stenosis or hypertrophic cardiomyopathy and bleeding disorders can change procedural safety.

How does Noonan syndrome affect dental management?

• Cardiology consult: valve lesion, cardiomyopathy, repair history; prophylaxis per AHA criteria
• Bleeding history and plan: Review personal/family bleeding and prior procedural outcomes; obtain a hematology-directed screen and hemostatic plan before invasive care.
• Laboratory limits: CBC, PT, and aPTT may be supplemented by factor, von Willebrand, or platelet-function studies; normal screening tests do not exclude every bleeding disorder.
• Hypertrophic cardiomyopathy: avoid tachycardia and dehydration; individualize epinephrine and anesthesia
• Orthodontics and diagnosis: Orthodontic referral for malocclusion; evaluate jaw radiolucencies

Exam pearl

What is Noonan syndrome?

A RAS/MAPK pathway disorder with variable short stature, characteristic facial features, congenital heart disease, and bleeding abnormalities.

What are the main systemic features of Noonan syndrome?

• Genetics: RASopathy; PTPN11 in ~50%, autosomal dominant; ~1 in 1,000–2,500
• Growth and body features: Turner-like features in both sexes: short stature, webbed neck, low posterior hairline, pectus deformity
• Face: Hypertelorism, down-slanting palpebral fissures, low-set posteriorly rotated ears, ptosis
• Heart: Pulmonary valve stenosis (most common, often dysplastic valve), hypertrophic cardiomyopathy
• Bleeding: Bleeding diathesis in up to half: factor XI deficiency, von Willebrand disease, platelet dysfunction
• Other features: Cryptorchidism, lymphatic problems, mild learning differences
• Differential: Noonan syndrome and neurofibromatosis type 1 are distinct conditions.

What oral findings occur in Noonan syndrome?

• Palate and jaws: High-arched palate, micrognathia, Class II and anterior open bite
• Occlusion: Dental crowding and malocclusion; articulation problems
• Jaw lesions: Giant cell lesions of the jaws (Noonan-like multiple giant cell lesion syndrome) in some

For Noonan syndrome, how does it differ from Turner syndrome?

Similar appearance: short stature, webbed neck.

A short child with a webbed neck and pulmonary valve stenosis needs extractions. What two systems do you clear?

• Cardiac: clarify pulmonary stenosis, hypertrophic cardiomyopathy, and repair status; use prophylaxis per AHA criteria.
• Bleeding: up to half have factor XI deficiency, von Willebrand disease, or platelet dysfunction. Obtain a CBC, PT, aPTT, and hematology input before surgery.

Sources

• AAPD dental guidance: AAPD: Antibiotic prophylaxis (2026 revision)
• Supplemental systemic features: MedlinePlus Genetics: noonan syndrome
• Supplemental study guide: Pediatric Dental Study Guide: Noonan Syndrome
• Management of Dental Patients with Special Health Care Needs
• Cardiology Consultation for Pediatric Dental Patients
• Hematology Consultation for Pediatric Dental Patients