PTPN11 mutation associated with aortic dilation and hypertrophic cardiomyopathy in a pediatric patient with Noonan syndrome

Multimodality Imaging in Noonan Syndrome: Case Series of Young Children

Noonan syndrome (NS) is an autosomal dominant disorder characterized by distinctive facial anomalies, growth failure, and a wide spectrum of cardiac abnormalities. Here, the clinical presentation, multimodality imaging characteristics, and management in a case series of four patients with NS are presented. Multimodality imaging showed frequently biventricular hypertrophy accompanied by biventricular outflow tract obstruction and pulmonary stenosis, similar late gadolinium enhancement pattern, and elevation of native T1 and extracellular volume, which may serve as multimodality imaging features in NS to aid in patient diagnosis and treatment. Keywords: Pediatrics, Echocardiography, MR Imaging, Cardiac Supplemental material is available for this article. © RSNA, 2023.

Coronary artery disease in adults with Noonan syndrome: Case series and literature review

Noonan syndrome (NS) is a genetic disorder characterized by facial dysmorphism, congenital heart disease, and short stature. In very rare cases, patients with this syndrome have coronary disease. Their management and prognosis are currently unclear. We have described 4 cases of coronary aneurysms/coronary ectasia and 1 case of a single coronary artery in patients with adult Noonan syndrome, followed in a medical and surgical center of adult congenital heart disease. The average age was 49.4years old. The majority of them had both pulmonary stenosis and interauricular communication. None had symptoms of angina, at rest, or with stress. Only one patient who had any structural heart disease, had a thrombotic complication with chronic occlusion of the right coronary and anterior inter ventricular artery, fortuitous finding, with no ischemic signs to functional tests, treated only with anti-vitamin K. Finally, any deaths have also been reported in our series. Coronary artery diseases essentially coronary aneurysm/ectasia remain a rare condition in adult patients with NS. Evolution is unknown and complications such as coronary artery thrombosis do not necessarily require surgical treatment.

Prevalence and Clinical Correlates of Aortic Dilation in Hypertrophic Cardiomyopathy

BACKGROUND

Aortic dilation has been associated with various cardiac conditions, although its prevalence and clinical correlates in hypertrophic cardiomyopathy (HCM) remain unclear.

OBJECTIVES

The purposes of this study were to define the prevalence of ascending aortic dilation in a large referral population of patients with HCM and to determine clinical and echocardiographic correlates of aortic dilation.

METHODS

A total of 1,698 patients with HCM underwent echocardiographic measurement of the tubular ascending aorta (proximal and midlevel) during index evaluation at a tertiary HCM referral center. End-diastolic ascending aorta dimension was indexed to body surface area, with dilation defined for the tubular ascending aorta as 2 SD above the mean (>19 mm/m²) and independently as greater than published age-, sex-, and body surface area- adjusted norms (for the sinus of Valsalva and midlevel). Aortic size and presence of aortic enlargement were correlated with clinical and echocardiographic parameters.

RESULTS

Tubular ascending aortic dilation >19 mm/m² was present in 303 patients with HCM (18%), and dilation above adjusted norms was present in 210 patients with HCM (13%). The median indexed tubular ascending thoracic aortic dimension was 16.5 (interquartile range, 14.8-18.2) mm/m². Indexed dimension increased linearly with age (R = 0.53, P < .0001). Women and patients with a history of systemic hypertension were more likely to have tubular aortic enlargement >19 mm/m² (29.8% vs 9.9% and 24.1% vs 10.5%, respectively, P < .0001 for both). Patients with obstructive physiology were more likely to have tubular aortic enlargement >19 mm/m² than those without resting or provocable obstruction (19.6% vs 14.4%, P = .007). Using adjusted norms, aortic enlargement was more frequent at the midlevel compared with the sinus of Valsalva (71% vs 29%), more common in patients with hypertension (15.4% vs 10.6%, P = .009), and more common in patients with paroxysmal atrial fibrillation (16.3% vs 11.5%, P = .036), but no other relationships remained statistically significant.

CONCLUSIONS

In this large cohort of patients with HCM, aortic dilation was common. The key correlate of tubular aortic enlargement >19 mm/m², and aortic enlargement greater than adjusted norms included a history of systemic hypertension. Given an increased prevalence of aortic dilation in HCM, further study is needed on the clinical impact of aortic dilation.

Cardiovascular disease in Noonan syndrome

BACKGROUND

Noonan syndrome (NS), a relatively common autosomal dominant disorder with an incidence of 1 in 1000 to 2500 live births, is the most common syndromic cause of congenital heart disease after Trisomy 21.

OBJECTIVE

To comprehensively define the spectrum of cardiac morphology and specific clinical course of a large cohort of NS patients.

DESIGN

Retrospective, descriptive case series study.

PATIENTS

An international Harvard-based NS registry was combined with clinical data from NS patients followed at Boston Children's Hospital, Massachusetts, USA.

RESULTS

We identified 293 patients with NS. Cardiovascular disease was seen in 81% (n=237) including pulmonary stenosis in 57%, secundum atrial septal defects in 32% and hypertrophic cardiomyopathy in 16%. A genetic mutation of the RAS-MAPK signalling pathway was identified in 62% (n=136). Genotype-phenotype associations were noted between PTPN11 mutations and atrial septal defects (p=0.001), and pulmonary stenosis (p<0.001). RAF1 mutations were associated with hypertrophic cardiomyopathy (p<0.001). Cardiovascular outcomes that differed specifically in a NS cohort included high re-intervention rates (65%) after percutaneous balloon pulmonary valvuloplasty for valvar pulmonary stenosis. Additionally, in NS patients with hypertrophic cardiomyopathy, a clinically significant regression of hypertrophy (17%) was observed as was a markedly higher incidence of concomitant congenital heart defects (70%).

CONCLUSIONS

Patients with NS have a distinct spectrum of cardiac phenotypes that may have a natural history and response to therapy atypical to that normally seen in non-syndromic heart disease. A diagnosis of NS in a patient with pulmonary stenosis or infant-onset hypertrophic cardiomyopathy would facilitate condition-specific counselling on outcome and prognosis.

Frequency of aortic dilation in Noonan syndrome

Noonan syndrome (NS) is a genetic disorder caused by mutations altering proteins relevant to RAS/mitogen-activated protein kinase signal transduction. Cardiac involvement is common, most prevalently pulmonary valve stenosis and hypertrophic cardiomyopathy. Because abnormal mitogen-activated protein kinase signaling contributes to the aortopathy in Marfan syndrome and with rare reports of aortic aneurysm in NS, we undertook a retrospective study of ascending aortic anatomy in 37 patients with NS and without confounding medical conditions. Age ranged from 0.6 to 32 years. Based on the most recent echocardiogram, the aortic annulus and root were dilated in the cohort (mean z scores of 1.14 and 0.98, respectively, p <0.005) but the sinotubular junction and ascending aorta were not (mean z scores of 0.05 and 0.19, respectively). The aortic root was aneurysmal (>2 z scores) in 8 subjects (21.6%). PTPN11 mutations were present in 14 subjects, whose aortic status was similar to the cohort overall. Comparison of age and z scores revealed a modest tendency for the aortic annulus and root to dilate over time. Among 13 subjects with multiple imaging studies over an average of 6.8 years, the average z score increased to 0.78 and 0.39 for the aortic annulus and root, respectively. Multivariate analysis revealed that age accounted for 7.0% and 11.0% of the variance in the aortic annular and root diameters, respectively. In conclusion, we found that aortic annular dilation and aortic root aneurysm are prevalent in NS, often presenting during childhood and progressing over time. Further study is needed to identify potential risks associated with these abnormalities.

Lethal presentation of neurofibromatosis and Noonan syndrome

Neurofibromatosis type 1 and Noonan syndrome are both common genetic disorders with autosomal dominant inheritance. Similarities between neurofibromatosis type 1 and Noonan syndrome have been noted for over 20 years and patients who share symptoms of both conditions are often given the diagnosis of neurofibromatosis-Noonan syndrome (NFNS). The molecular basis of these combined phenotypes was poorly understood and controversially discussed over several decades until the discovery that the syndromes are related through disturbances of the Ras pathway. We present an infant male with coarse facial features, severe supravalvar pulmonic stenosis, automated atrial tachycardia, hypertrophic cardiomyopathy, airway compression, severe neurological involvement, and multiple complications that lead to death during early infancy. The severity of clinical presentation and significant dysmorphic features suggested the possibility of a double genetic disorder in the Ras pathway instead of NFNS. Molecular analysis showed a missense mutation in exon 25 of the NF1 gene (4288A>G, p.N1430D) and a pathogenic mutation on exon 8 (922A>G, p.N308D) of the PTPN11 gene. Cardiovascular disease has been well described in patients with Noonan syndrome with PTPN11 mutations but the role of haploinsufficiency for neurofibromin in the heart development and function is not yet well understood. Our case suggests that a double genetic defect resulting in the hypersignaling of the Ras pathway may lead to complex cardiovascular abnormalities, cardiomyopathy, refractory arrhythmia, severe neurological phenotype, and early death.