Noonan syndrome imaging findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Serge Korjian, Yazan Daaboul


The most important imaging modality in Noonan syndrome is the echocardiogram that can reveal pulmonary valve dysplasia or pulmonary valve stenosis, ventricular hypertrophy and septal defects.

Imaging Findings

Several imaging findings can aid in the diagnosis of Noonan syndrome:

  • Echocardiograms can show pulmonary valve dysplasia or significant pulmonary valve stenosis. Both right and left ventricular hypertrophy with mild to moderate increase in the thickness of the free wall and septum can be detected. Other abnormalites include septal defects most commonly secundum atrial septal defects. [1] Pulmonary valve recordings can show poor a wave definition. [2]
  • Although prenatal ultrasound is not very specific for the diagnosis of Noonan syndrome, some features are indicative. Some fetuses can show cystic hygromata located laterally along the cervical spine. Other findings may include polyhydramnios, pleural effusions, hydronephrosis, cardiac defects, and increased nuchal translucency.[3][4]
  • Plain film chest x-rays are usually normal with cardiothoracic ratio not necessarily indicative of disease severity.
  • Roentgenograms can show pectus excavatum or carinatum. [5]
  • Abdominal ultrasound is usually normal but can sometimes show hepatosplenomegaly or renal abnormalities. [6]


  1. Burch M, Sharland M, Shinebourne E, Smith G, Patton M, McKenna W (1993). "Cardiologic abnormalities in Noonan syndrome: phenotypic diagnosis and echocardiographic assessment of 118 patients". J Am Coll Cardiol. 22 (4): 1189–92. PMID 8409059.
  2. Holder AA, Wootton JC, Baron AJ, Chambers GK, Fincham JR (1975). "The amino acid sequence of Neurospora NADP-specific glutamate dehydrogenase. Peptic and chymotryptic peptides and the complete sequence". Biochem J. 149 (3): 757–73. PMC 1165685. PMID 0.1002/ajmg.1320100106 Check |pmid= value (help).
  3. Benacerraf BR, Greene MF, Holmes LB (1989). "The prenatal sonographic features of Noonan's syndrome". J Ultrasound Med. 8 (2): 59–63. PMID 2651692.
  4. Nisbet DL, Griffin DR, Chitty LS (1999). "Prenatal features of Noonan syndrome". Prenat Diagn. 19 (7): 642–7. PMID 10419612‎ Check |pmid= value (help).
  5. Duncan WJ, Fowler RS, Farkas LG, Ross RB, Wright AW, Bloom KR; et al. (1981). "A comprehensive scoring system for evaluating Noonan syndrome". Am J Med Genet. 10 (1): 37–50. doi:10.1002/ajmg.1320100106. PMID 7294061.
  6. George CD, Patton MA, el Sawi M, Sharland M, Adam EJ (1993). "Abdominal ultrasound in Noonan syndrome: a study of 44 patients". Pediatr Radiol. 23 (4): 316–8. PMID 8414765‎ Check |pmid= value (help).

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