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Noonan Syndrome Cardiac Features — EECC MCQ

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ModerateCongenital Heart Disease (Adult)Noonan Syndrome Cardiac FeaturesEECC

A 50-year-old man with Noonan syndrome has mild pulmonary valve stenosis and HCM-like LVH. What cardiac features are associated with Noonan syndrome?

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Correct answer: C — Pulmonary valve stenosis (most common ~50-60%), HCM phenotype (20-30%), ASD, and AVSD — Noonan syndrome is a RASopathy caused by mutations in the RAS-MAPK signalling pathway (PTPN11 most common)

Noonan syndrome is the most common syndromic cause of congenital heart disease (1 in 1000-2500 births). Cardiac features include: (1) pulmonary valve stenosis (most common, ~50-60% — often dysplastic valve with poor PMBC response); (2) HCM phenotype (20-30% — biventricular, often with LVOT obstruction; may present in infancy and can be severe); (3) ASD (particularly secundum type); (4) AVSD; (5) other: coarctation, PAPVD. Noonan syndrome is a RASopathy (PTPN11 mutations in ~50%, RAF1, SOS1, KRAS, BRAF, and others). The 2023 ESC Cardiomyopathy Guidelines classify Noonan HCM as a phenocopy — mavacamten (designed for sarcomeric HCM) is not appropriate. Management is supportive: beta-blockers for LVOT obstruction, myectomy if refractory, and standard pulmonary stenosis interventions.

Reference: ESC (2023): Cardiomyopathies Guidelines; ESC (2020): ACHD Guidelines