Clinical Presentation and Natural History of Hypertrophic Cardiomyopathy in RASopathies

Cardiac Phenotype and Gene Mutations in RASopathies

Cardiac involvement is a major feature of RASopathies, a group of phenotypically overlapping syndromes caused by germline mutations in genes encoding components of the RAS/MAPK (mitogen-activated protein kinase) signaling pathway. In particular, Noonan syndrome (NS) is associated with a wide spectrum of cardiac pathologies ranging from congenital heart disease (CHD), present in approximately 80% of patients, to hypertrophic cardiomyopathy (HCM), observed in approximately 20% of patients. Genotype-cardiac phenotype correlations are frequently described, and they are useful indicators in predicting the prognosis concerning cardiac disease over the lifetime. The aim of this review is to clarify the molecular mechanisms underlying the development of cardiac diseases associated particularly with NS, and to discuss the main morphological and clinical characteristics of the two most frequent cardiac disorders, namely pulmonary valve stenosis (PVS) and HCM. We will also report the genotype-phenotype correlation and its implications for prognosis and treatment. Knowing the molecular mechanisms responsible for the genotype-phenotype correlation is key to developing possible targeted therapies. We will briefly address the first experiences of targeted HCM treatment using RAS/MAPK pathway inhibitors.

Defining the variant-phenotype correlation in patients affected by Noonan syndrome with the RAF1:c.770C>T p.(Ser257Leu) variant

Hypertrophic cardiomyopathy (HCM) is the major contributor to morbidity and mortality in Noonan syndrome (NS). Gain-of-function variants in RAF1 are associated with high prevalence of HCM. Among these, NM_002880.4:c.770C > T, NP_002871.1:p.(Ser257Leu) accounts for approximately half of cases and has been reported as associated with a particularly severe outcome. Nevertheless, comprehensive studies on cases harboring this variant are missing. To precisely define the phenotype associated to the RAF1:c.770C > T, variant, an observational retrospective analysis on patients carrying the c.770C > T variant was conducted merging 17 unpublished patients and literature-derived ones. Data regarding prenatal findings, clinical features and cardiac phenotypes were collected to provide an exhaustive description of the associated phenotype. Clinical information was collected in 107 patients. Among them, 92% had HCM, mostly diagnosed within the first year of life. Thirty percent of patients were preterm and 47% of the newborns was admitted in a neonatal intensive care unit, mainly due to respiratory complications of HCM and/or pulmonary arterial hypertension. Mortality rate was 13%, mainly secondary to HCM-related complications (62%) at the average age of 7.5 months. Short stature had a prevalence of 91%, while seizures and ID of 6% and 12%, respectively. Two cases out of 75 (3%) developed neoplasms. In conclusion, patients with the RAF1:c.770C > T pathogenic variant show a particularly severe phenotype characterized by rapidly progressive neonatal HCM and high mortality rate suggesting the necessity of careful monitoring and early intervention to prevent or slow down the progression of HCM.

Treatment of RAF1-Related Obstructive Hypertrophic Cardiomyopathy by MEK Inhibition Using Trametinib

RASopathies cause nonsarcomeric hypertrophic cardiomyopathy via dysregulated signaling through RAS and upregulated mitogen-activated protein kinase activity. We provide the first report of the successful treatment of an adult with RAF1-associated hypertrophic cardiomyopathy using trametinib, a MEK inhibitor.

Exploring New Drug Repurposing Opportunities for MEK Inhibitors in RASopathies: A Comprehensive Review of Safety, Efficacy, and Future Perspectives of Trametinib and Selumetinib

The RASopathies are a group of syndromes caused by genetic variants that affect the RAS-MAPK signaling pathway, which is essential for cell response to diverse stimuli. These variants functionally converge towards the overactivation of the pathway, leading to various constitutional and mosaic conditions. These syndromes show overlapping though distinct clinical presentations and share congenital heart defects, hypertrophic cardiomyopathy (HCM), and lymphatic dysplasia as major clinical features, with highly variable prevalence and severity. Available treatments have mainly been directed to target the symptoms. However, repurposing MEK inhibitors (MEKis), which were originally developed for cancer treatment, to target evolutive aspects occurring in these disorders is a promising option. Animal models have shown encouraging results in treating various RASopathy manifestations, including HCM and lymphatic abnormalities. Clinical reports have also provided first evidence supporting the effectiveness of MEKi, especially trametinib, in treating life-threatening conditions associated with these disorders. Nevertheless, despite notable improvements, there are adverse events that occur, necessitating careful monitoring. Moreover, there is evidence indicating that multiple pathways can contribute to these disorders, indicating a current need to more accurate understand of the underlying mechanism of the disease to apply an effective targeted therapy. In conclusion, while MEKi holds promise in managing life-threatening complications of RASopathies, dedicated clinical trials are required to establish standardized treatment protocols tailored to take into account the individual needs of each patient and favor a personalized treatment.

MEK Inhibition for RASopathy-Associated Hypertrophic Cardiomyopathy: Clinical Application of a Basic Concept

The term "RASopathies" designates a group of developmental syndromes that are caused by activating variants of the rat sarcoma virus protein (RAS)/mitogen-activated protein kinase (MAPK) cascade. The most prevalent clinical diagnosis is Noonan syndrome, and other, less prevalent conditions include Noonan syndrome with multiple lentigines, Costello syndrome, cardiofaciocutaneous syndrome, and others. Hypertrophic cardiomyopathy occurs in 10% of these patients and can be severe and life-threating. Recently, repurposing of medications inhibiting the RAS/MAPK on a compassionate use basis has emerged as a promising concept to improve the outcome of these patients. Herein, we specifically review the role of the RAS/MAPK pathway in RASopathy-associated cardiomyopathy, and discuss the role of small-molecule inhibition in the treatment of this condition. We describe how drug repurposing of trametinib (mitogen-activated protein/extracellular signal-regulated kinase inhibition) and sirolimus/everolimus (mammalian target of rapamycin inhibition) was performed, how genotype-specific therapies are chosen and followed, as well as initial outcomes from early case series. Finally, we lay out the challenges and opportunities for trials that aim to quantify the benefits of this approach.

RASopathies for Radiologists

RASopathies are a heterogeneous group of genetic syndromes caused by germline mutations in a group of genes that encode components or regulators of the Ras/mitogen-activated protein kinase (MAPK) signaling pathway. RASopathies include neurofibromatosis type 1, Legius syndrome, Noonan syndrome, Costello syndrome, cardiofaciocutaneous syndrome, central conducting lymphatic anomaly, and capillary malformation-arteriovenous malformation syndrome. These disorders are grouped together as RASopathies based on our current understanding of the Ras/MAPK pathway. Abnormal activation of the Ras/MAPK pathway plays a major role in development of RASopathies. The individual disorders of RASopathies are rare, but collectively they are the most common genetic condition (one in 1000 newborns). Activation or dysregulation of the common Ras/MAPK pathway gives rise to overlapping clinical features of RASopathies, involving the cardiovascular, lymphatic, musculoskeletal, cutaneous, and central nervous systems. At the same time, there is much phenotypic variability in this group of disorders. Benign and malignant tumors are associated with certain disorders. Recently, many institutions have established multidisciplinary RASopathy clinics to address unique therapeutic challenges for patients with RASopathies. Medications developed for Ras/MAPK pathway-related cancer treatment may also control the clinical symptoms due to an abnormal Ras/MAPK pathway in RASopathies. Therefore, radiologists need to be aware of the concept of RASopathies to participate in multidisciplinary care. As with the clinical manifestations, imaging features of RASopathies are overlapping and at the same time diverse. As an introduction to the concept of RASopathies, the authors present major representative RASopathies, with emphasis on their imaging similarities and differences. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Combined Pharmacological Modulation of Translational and Transcriptional Activity Signaling Pathways as a Promising Therapeutic Approach in Children with Myocardial Changes

Myocardial hypertrophy is the most common condition that accompanies heart development in children. Transcriptional gene expression regulating pathways play a critical role both in cardiac embryogenesis and in the pathogenesis of congenital hypertrophic cardiomyopathy, neonatal posthypoxic myocardial hypertrophy, and congenital heart diseases. This paper describes the state of cardiac gene expression and potential pharmacological modulators at different transcriptional levels. An experimental model of perinatal cardiac hypoxia showed the downregulated expression of genes responsible for cardiac muscle integrity and overexpressed genes associated with energy metabolism and apoptosis, which may provide a basis for a therapeutic approach. Current evidence suggests that RNA drugs, theaflavin, neuraminidase, proton pumps, and histone deacetylase inhibitors are promising pharmacological agents in progressive cardiac hypertrophy. The different points of application of the above drugs make combined use possible, potentiating the effects of inhibition in specific signaling pathways. The special role of N-acetyl cysteine in both the inhibition of several signaling pathways and the reduction of oxidative stress was emphasized.

Natural history and outcomes in paediatric RASopathy-associated hypertrophic cardiomyopathy

AIMS

This study aimed to describe the natural history and predictors of all-cause mortality and sudden cardiac death (SCD)/equivalent events in children with a RASopathy syndrome and hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

This is a retrospective cohort study from 14 paediatric cardiology centres in the United Kingdom and Ireland. We included children <18 years with HCM and a clinical and/or genetic diagnosis of a RASopathy syndrome [Noonan syndrome (NS), NS with multiple lentigines (NSML), Costello syndrome (CS), cardiofaciocutaneous syndrome (CFCS), and NS with loose anagen hair (NS-LAH)]. One hundred forty-nine patients were recruited [111 (74.5%) NS, 12 (8.05%) NSML, 6 (4.03%) CS, 6 (4.03%) CFCS, 11 (7.4%) Noonan-like syndrome, and 3 (2%) NS-LAH]. NSML patients had higher left ventricular outflow tract (LVOT) gradient values [60 (36-80) mmHg, P = 0.004]. Over a median follow-up of 197.5 [inter-quartile range (IQR) 93.58-370] months, 23 patients (15.43%) died at a median age of 24.1 (IQR 5.6-175.9) months. Survival was 96.45% [95% confidence interval (CI) 91.69-98.51], 90.42% (95% CI 84.04-94.33), and 84.12% (95% CI 75.42-89.94) at 1, 5, and 10 years, respectively, but this varied by RASopathy syndrome. RASopathy syndrome, symptoms at baseline, congestive cardiac failure (CCF), non-sustained ventricular tachycardia (NSVT), and maximal left ventricular wall thickness were identified as predictors of all-cause mortality on univariate analysis, and CCF, NSVT, and LVOT gradient were predictors for SCD or equivalent event.

CONCLUSIONS

These findings highlight a distinct category of patients with Noonan-like syndrome with a milder HCM phenotype but significantly worse survival and identify potential predictors of adverse outcome in patients with RASopathy-related HCM.

Genetic Testing in Hypertrophic Cardiomyopathy

Genetic testing is an important tool in the diagnosis and management of patients and families with hypertrophic cardiomyopathy (HCM). Modern testing can identify causative variants in 30 to >60% of patients, with probability of a positive test varying with baseline characteristics such as known family history of HCM. Patients diagnosed with HCM should be offered genetic counseling and genetic testing as appropriate. Standard multigene panels evaluate sarcomeric genes known to cause HCM as well as genetic conditions that can mimic HCM but require different management. Positive genetic testing (finding a pathogenic or likely pathogenic variant) helps to clarify diagnosis and assists in family screening. If there is high confidence that an identified variant is the cause of HCM, at-risk family members can pursue predictive testing to determine if they are truly at risk or if they can be dismissed from serial screening based on whether they inherited the family's causative variant. Interpreting test results can be complex, and providers should make use of multidisciplinary teams as well as evidence-based resources to obtain the best possible understanding of pathogenicity.

RAF1 mutation leading to hypertrophic cardiomyopathy in a Chinese family with a history of sudden cardiac death: A diagnostic insight into Noonan syndrome

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is predominantly caused by mutations in sarcomeric genes. However, a subset of cases is attributed to genetic disorders unrelated to sarcomeric genes, such as Noonan syndrome (NS) and other RASopathies. In this study, we present a family with a history of sudden cardiac death (SCD) and focus on two adults with syndromic left ventricular hypertrophy (LVH).

METHODS

Clinical evaluations, including echocardiography, were conducted to assess cardiac manifestations. Whole-exome sequencing was performed to identify potential genetic variants underlying syndromic LVH in the study participants.

RESULTS

Whole-exome sequencing revealed a missense variant in the RAF1 gene, c.782C>T (p.Pro261Leu). This variant confirmed the diagnosis of NS in the affected individuals.

CONCLUSION

The findings of this study underscore the importance of family history investigation and genetic testing in diagnosing syndromic LVH. By identifying the underlying genetic cause, clinicians can better understand the etiology of RAS-HCM and its association with SCD in young adults.

Risk of Sudden Death in Patients With RASopathy Hypertrophic Cardiomyopathy

BACKGROUND

Genetic defects in the RAS/mitogen-activated protein kinase pathway are an important cause of hypertrophic cardiomyopathy (RAS-HCM). Unlike primary HCM (P-HCM), the risk of sudden cardiac death (SCD) and long-term survival in RAS-HCM are poorly understood.

OBJECTIVES

The study's objective was to compare transplant-free survival, incidence of SCD, and implantable cardioverter-defibrillator (ICD) use between RAS-HCM and P-HCM patients.

METHODS

In an international, 21-center cohort study, we analyzed phenotype-positive pediatric RAS-HCM (n = 188) and P-HCM (n = 567) patients. The between-group differences in cumulative incidence of all outcomes from first evaluation were compared using Gray's tests, and age-related hazard of all-cause mortality was determined.

RESULTS

RAS-HCM patients had a lower median age at diagnosis compared to P-HCM (0.9 years [IQR: 0.2-5.0 years] vs 9.8 years [IQR: 2.0-13.9 years], respectively) (P < 0.001). The 10-year cumulative incidence of SCD from first evaluation was not different between RAS-HCM and P-HCM (4.7% vs 4.2%, respectively; P = 0.59). The 10-year cumulative incidence of nonarrhythmic deaths or transplant was higher in RAS-HCM compared with P-HCM (11.0% vs 5.4%, respectively; P = 0.011). The 10-year cumulative incidence of ICD insertions, however, was 5-fold lower in RAS-HCM compared with P-HCM (6.9% vs 36.6%; P < 0.001). Nonarrhythmic deaths occurred primarily in infancy and SCD primarily in adolescence.

CONCLUSIONS

RAS-HCM was associated with a higher incidence of nonarrhythmic death or transplant but similar incidence of SCD as P-HCM. However, ICDs were used less frequently in RAS-HCM compared to P-HCM. In addition to monitoring for heart failure and timely consideration of advanced heart failure therapies, better risk stratification is needed to guide ICD practices in RAS-HCM.

Role of cardiovascular magnetic resonance in the clinical evaluation of left ventricular hypertrophy: a 360° panorama

Left ventricular hypertrophy (LVH) is a frequent imaging finding in the general population. In order to identify the precise etiology, a comprehensive diagnostic approach should be adopted, including the prevalence of each entity that may cause LVH, family history, clinical, electrocardiographic and imaging findings. By providing a detailed evaluation of the myocardium, cardiovascular magnetic resonance (CMR) has assumed a central role in the differential diagnosis of left ventricular hypertrophy, with the technique of parametric imaging allowing more refined tissue characterization. This article aims to establish a parallel between pathophysiological features and imaging findings through the broad spectrum of LVH entities, emphasizing the role of CMR in the differential diagnosis.

Endocrinological manifestations in RASopathies

The evaluation of endocrine involvement in RASopathies is important for the care and follow-up of patients affected by these conditions. Short stature is a cardinal feature of RASopathies and correlates with multiple factors. Growth hormone treatment is a therapeutic possibility to improve height and quality of life. Assessment of growth rate and growth laboratory parameters is routine, but age at start of therapy, dose and effects of growth hormone on final height need to be clarified. Puberty disorders and gonadal dysfunction, in particular in males, are other endocrinological areas to evaluate for their effects on growth and development. Thyroid dysfunction, autoimmune disease and bone involvement have also been reported in RASopathies. In this brief review, we describe the current knowledge on growth, growth hormone therapy, endocrinological involvement in patients affected by RASopathies.

New prospectives on treatment opportunities in RASopathies

The RASopathies are a group of clinically defined developmental syndromes caused by germline variants of the RAS/mitogen-activated protein (MAPK) cascade. The prototypic RASopathy is Noonan syndrome, which has phenotypic overlap with related disorders such as cardiofaciocutaneous syndrome, Costello syndrome, Noonan syndrome with multiple lentigines, and others. In this state-of-the-art review, we summarize current knowledge on unmet therapeutic needs in these diseases and novel treatment approaches informed by insights from RAS/MAPK-associated cancer therapies, in particular through inhibition of MEK1/2 and mTOR in patients with severe disease manifestations. We explore the possibilities of integrating a larger arsenal of molecules currently under development into future care plans. Lastly, we describe both medical and ethical challenges and opportunities for future clinical trials in the field.

Molecular and clinical profile of patients referred as Noonan or Noonan-like syndrome in Greece: a cohort of 86 patients

Noonan syndrome (NS) is an autosomal dominant disorder characterized by clinical and genetic heterogeneity. It belongs to a wider group of pathologies, known as Rasopathies, due to the implication of genes encoding components of the Ras/MAPK signalling pathway. Recording the genetic alterations across populations helps assessing specific features to specific genes which is essential for better disease's recognition, prognosis and monitoring. Herein, we report the clinical and molecular data of a Greek cohort comprising of 86 NS or NS-like patients admitted at a single tertiary Centre in Athens, Greece. The analysis was performed using Sanger and next-generation sequencing, comprising 14 different genes. The mutational rates of the confirmed NS-associated genes in the Greek NS population are as follows: PTPN11 32.5%; RIT1 5.8%; SOS1 4.7%; BRAF 1.2%; CBL 1.2%; KRAS 1.2%; MAP2K1 1.2%; RAF1 1.2%; SHOC2 1.2%, corresponding to 50% of positivity in total NS population. The genotype-phenotype analysis showed statistically significant differences in craniofacial dysmorphisms (p = 0.005) and pulmonary valve stenosis (PS) (p < 0.001) frequencies between patients harbouring a pathogenic variant and patients without pathogenic variant in any of the tested genes. Patients with at least a pathogenic variant had 6.71 times greater odds to develop PS compared to pathogenic variant-negative patients (OR = 6.71, 95%; CI = (2.61, 17.27)). PTPN11 positive patients showed higher frequency of epicanthal folds (p = 0.004), ptosis (p = 0.001) and coarseness (p = 0.001) and lower frequency of neurological findings (p = 0.006), compared to patients carrying pathogenic variants in other genes.

CONCLUSION

Craniofacial dysmorphism and PS prevail among pathogenic variant positive compared to pathogenic variant negative NS and NS-like patients while neurological defects are less common in PTPN11-affected NS patients compared to patients harbouring pathogenic variants in other genes. The significant prevalence of the Ras/MAPK pathogenic variants (17.4%), other than PTPN11, in Greek NS patients, highlights the necessity of a wider spectrum of molecular diagnosis.

WHAT IS KNOWN

• Noonan syndrome (NS) has been associated with pathogenic variants in molecules-components of the Ras/MAPK pathway. • Clinical and genetic description of NS patients worldwide helps establishing personalized monitoring.

WHAT IS NEW

• NS and NS-like mutational rate in Greece reaches 50% with pathogenic variants identified mostly in PTPN11 (32.5%), RIT1 (6%) and SOS1 (4.7%) genes. • The risk for pulmonary stenosis increases 6.71-fold in NS patients with a pathogenic variant compared to patients without genetic alterations.

Clinical characteristics and survival of children with hypertrophic cardiomyopathy in China: A multicentre retrospective cohort study

BACKGROUND

Few data on paediatric hypertrophic cardiomyopathy (HCM) are available in developing countries. A multicentre, retrospective, cohort study was conducted to profile the clinical characteristics and survival of children with HCM in China.

METHODS

We collected longitudinal data on children with HCM aged 0-18 years at three participating institutions between January 1, 2010 and December 31, 2019. Patients were identified by searching for the diagnosis using ICD-10 codes from the electronic medical records database. HCM was diagnosed morphologically with echocardiography or cardiovascular magnetic resonance imaging. The exclusion criteria were secondary aetiologies of myocardial hypertrophy. The primary outcomes were all-cause death or heart transplantation. The Kaplan-Meier method was used to estimate the survival rate of different groups.

FINDINGS

A total of 564 children were recruited, with a median age at diagnosis of 1.0 year (interquartile range, IQR: 0.4-8.0 years), followed for a median of 2.6 years (1977 patient-years, IQR:0.5, 5.9 years). The underlying aetiology was sarcomeric (382, 67.7%), inborn errors of metabolism (IEMs) (108, 19.2%), and RASopathies (74, 13.1%). A total of 149 patients (26.4%) died and no patients underwent heart transplantation during follow-up. The survival probability was 71.1% (95% confidence interval [CI], 66.3%-75.3%) at 5 years. Patients with IEMs or those diagnosed during infancy had the poorest outcomes, with an estimated 5-year survival rate of 16.9% (95% CI, 7.7%-29.1%) and 56.0% (95% CI, 48.8%-62.5%), respectively. Heart failure was the leading cause of death in the cohort (90/149, 60.4%), while sudden cardiac death was the leading cause in patients with sarcomeric HCM (32/66, 48.5%).

INTERPRETATION

There is a high proportion of patients with IEM and a low proportion of patients with neuromuscular disease in children with HCM in China. Overall, mortality remains high in China, especially in patients with IEMs and those diagnosed during infancy.

FUNDING

National Natural Science Fund of China (81770380, 81974029), China Project of Shanghai Municipal Science and Technology Commission (20MC1920400, 21Y31900301).

Cardiovascular Abnormalities and Gene Mutations in Children With Noonan Syndrome

Background: Common cardiac abnormalities in Noonan syndrome (NS) include congenital heart diseases (CHD), pulmonary valve stenosis and hypertrophic cardiomyopathy (HCM). Molecular diagnoses are enabling earlier and more precise diagnosis of patients who have a subtle or atypical presentation. The aims of this study were to investigate genotype-phenotype associations with respect to Noonan syndrome (NS)-associated cardiac abnormalities and catheter or surgery-based interventions conditions.

Methods: From January 2019 to December 2021, 22 children with a confirmed molecular diagnosis of NS combined with cardiovascular abnormalities were consecutively enrolled into the current study. A comprehensive review was carried out of echocardiography and electrocardiogram results, second-generation whole-exome sequencing results and catheter or surgery-based interventions conditions.

Results: The main manifestations of electrocardiogram abnormalities were QTc prolongation, abnormal Q wave in the precordial lead and limb lead, right ventricular hypertrophy and left or right deviation of the electrical axis. The most commonly detected abnormality was pulmonary valve dysplasia with stenosis, seen in 15 (68.2%) patients, followed by atrial septal defect in 11 (50%) patients. Seven genes (RAF1, RIT1, SOS1, PTPN11, BRAF, SOS2, and LZTR1) were found to contain disease-associated variants. The most commonly observed genetic mutations were PTPN11 (27%) and RAF1 (27%). Each genotype was associated with specific phenotypic findings. RIT1, SOS1, PTPN11, and SOS2 had common echocardiography features characterized by pulmonary valve stenosis, while RAF1 was characterized by HCM. Interestingly, patients with BRAF mutations were not only characterized by HCM, but also by pulmonary valve stenosis. In the cohort there was only one patient carrying a LZTR1 mutation characterized by left ventricle globose dilation. Ten cases underwent catheter or surgery-based interventions. All the operations had immediate results and high success rates. However, some of the cases had adverse outcomes during extended follow-up. Based on the genotype-phenotype associations observed during follow-up, BRAF and RAF1 genotypes seem to be poor prognostic factors, and multiple interventions may be required for NS patients with severe pulmonary stenosis or myectomy for HCM.

Conclusions: The identification of causal genes in NS patients has enabled the evaluation of genotype-cardiac phenotype relationships and prognosis of the disease. This may be beneficial for the development of therapeutic approaches.

Cardiac features of Noonan syndrome in Japanese patients

BACKGROUND

Cardiovascular disease is one of the most important problems in long-term follow-up for Noonan syndrome. We examined cardiovascular issues and clinical manifestations, with a focus on the cardiovascular disease and prognosis of patients with Noonan syndrome.

METHODS

This single-centre study evaluated patients who were clinically and genetically diagnosed with Noonan syndrome.

RESULTS

Forty-three patients diagnosed with Noonan syndrome were analysed. The most prevalent responsible mutation was found in PTPN11 (25/43). The second and third most prevalent causative genes were SOS1 (6/43) and RIT1 (5/43), respectively, and 67.4% of genetically diagnosed patients with Noonan syndrome had structural cardiovascular abnormalities. Pulmonary valve stenosis was prevalent in patients with mutations in PTPN11 (8/25), SOS1 (4/6), and RIT1 (4/5). Hypertrophic cardiomyopathy was found in two of three patients with mutations in RAF1. There was no difference in the cardiovascular events or cardiovascular disease prevalence in patients with or without PTPN11 mutations. The proportion of RIT1 mutation-positive patients who underwent intervention due to cardiovascular disease was significantly higher than that of patients with PTPN11 mutations. Patients who underwent any intervention for pulmonary valve stenosis exhibited significantly higher pulmonary flow velocity than patients who did not undergo intervention, when they visited our hospital for the first time. All patients who underwent intervention for pulmonary valve stenosis had a pulmonary flow velocity of more than 3.0 m/s at first visit.

CONCLUSIONS

These findings suggest that genetic information can provide a clinical prognosis for cardiovascular disease and may be part of genotype-based follow-up in Noonan syndrome.

Growth, Endocrine Features, and Growth Hormone Treatment in Noonan Syndrome

Noonan syndrome is a heterogeneous congenital disorder. The main features are typical facial features, short stature and cardiac defects. The diagnosis is clinical: in 80% of patients with Noonan syndrome a genetic defect can be shown. Inheritance is predominantly autosomal dominant and seldom autosomal recessive. In 2001, PTPN11 was the first gene connected to Noonan syndrome, and until now, at least 20 other genes have been discovered. All genes code for proteins involved in the RAS-MAP-kinase pathway, and therefore, Noonan syndrome is one of the known RASopathies. Other RASopathies include neurofibromatosis and CFC syndrome. Short stature is one of the defining features of Noonan syndrome. The cause is not fully understood but is multifactorial. Other endocrinological features are confined to delayed puberty and hypogonadism in boys and males. To increase adult height, children with Noonan syndrome have been treated with human growth hormone since the 1990s. This seems to be beneficial in most of the children treated. In this narrative review, we describe the current knowledge on growth, endocrinological features and growth hormone treatment in patients with Noonan syndrome.

Diagnosis and Management of Rare Cardiomyopathies in Adult and Paediatric Patients. A Position Paper of the Italian Society of Cardiology (SIC) and Italian Society of Paediatric Cardiology (SICP)

Cardiomyopathies (CMPs) are myocardial diseases in which the heart muscle is structurally and functionally abnormal in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. Thought for a long time to be rare diseases, it is now clear that most of the CMPs can be easily observed in clinical practice. However, there is a group of specific heart muscle diseases that are rare in nature whose clinical/echocardiographic phenotypes resemble those of the four classical morphological subgroups of hypertrophic, dilated, restrictive, arrhythmogenic CMPs. These rare CMPs, often but not solely diagnosed in infants and paediatric patients, should be more properly labelled as specific CMPs. Emerging consensus exists that these conditions require tailored investigation and management. Indeed, an appropriate understanding of these conditions is mandatory for early treatment and counselling. At present, however, the multisystemic and heterogeneous presentation of these entities is a challenge for clinicians, and time delay in diagnosis is a significant concern. The aim of this paper is to define practical recommendations for diagnosis and management of the rare CMPs in paediatric or adult age. A modified Delphi method was adopted to grade the recommendations proposed by each member of the writing committee.

Cardiomyopathies in Children and Systemic Disorders When Is It Useful to Look beyond the Heart?

Cardiomyopathy (CMP) is a rare disease in the pediatric population, with a high risk of morbidity and mortality. The genetic etiology of CMPs in children is extremely heterogenous. These two factors play a major role in the difficulties of establishing standard diagnostic and therapeutic protocols. Isolated CMP in children is a frequent finding, mainly caused by sarcomeric gene variants with a detection rate that can reach up to 50% of analyzed cohorts. Complex multisystemic forms of pediatric CMP are even more heterogenous. Few studies in literature take into consideration this topic as the main core since it represents a rarity (systemic CMP) within a rarity (pediatric population CMP). Identifying etiology in this cohort is essential for understanding prognosis, risk stratification, eligibility to heart transplantation and/or mechanical-assisted procedures, preventing multiorgan complications, and relatives' recurrence risk calculation. The previous points represent a cornerstone in patients' empowerment and personalized medical care approach. The aim of this work is to propose a new approach for an algorithm in the setting of the diagnostic framework of systemic pediatric CMP. On the other hand, during the literature review, we noticed a relatively common etiologic pattern in some forms of complex/multisystem CMP. In other words, certain syndromes such as Danon, Vici, Alström, Barth, and Myhre syndrome share a common pathway of directly or indirectly defective "autophagy" process, which appears to be a possible initiating/triggering factor for CMPs. This conjoint aspect could be important for possible prognostic/therapeutic implications in this category of patients. However, multicentric studies detailed functional and experimental models are needed prior to deriving conclusions.

Cell cycle defects underlie childhood-onset cardiomyopathy associated with Noonan syndrome

Childhood-onset myocardial hypertrophy and cardiomyopathic changes are associated with significant morbidity and mortality in early life, particularly in patients with Noonan syndrome, a multisystemic genetic disorder caused by autosomal dominant mutations in genes of the Ras-MAPK pathway. Although the cardiomyopathy associated with Noonan syndrome (NS-CM) shares certain cardiac features with the hypertrophic cardiomyopathy caused by mutations in sarcomeric proteins (HCM), such as pathological myocardial remodeling, ventricular dysfunction, and increased risk for malignant arrhythmias, the clinical course of NS-CM significantly differs from HCM. This suggests a distinct pathophysiology that remains to be elucidated. Here, through analysis of sarcomeric myosin conformational states, histopathology, and gene expression in left ventricular myocardial tissue from NS-CM, HCM, and normal hearts complemented with disease modeling in cardiomyocytes differentiated from patient-derived PTPN11 N308S/+ induced pluripotent stem cells, we demonstrate distinct disease phenotypes between NS-CM and HCM and uncover cell cycle defects as a potential driver of NS-CM.

Hypertrophic Cardiomyopathy in RASopathies: Diagnosis, Clinical Characteristics, Prognostic Implications, and Management

RASopathies are multisystemic disorders caused by germline mutations in genes linked to the RAS/mitogen-activated protein kinase pathway. Diagnosis of RASopathy can be triggered by clinical clues ("red flags") which may direct the clinician toward a specific gene test. Compared with sarcomeric hypertrophic cardiomyopathy, hypertrophic cardiomyopathy in RASopathies (R-HCM) is associated with higher prevalence of congestive heart failure and shows increased prevalence and severity of left ventricular outflow tract obstruction. Biventricular involvement and the association with congenital heart disease, mainly pulmonary stenosis, have been commonly described in R-HCM. The aim of this review is to assess the prevalence and unique features of R-HCM and to define the available therapeutic options.

MEK Inhibition in a Newborn with RAF1-Associated Noonan Syndrome Ameliorates Hypertrophic Cardiomyopathy but Is Insufficient to Revert Pulmonary Vascular Disease

The RAF1:p.Ser257Leu variant is associated with severe Noonan syndrome (NS), progressive hypertrophic cardiomyopathy (HCM), and pulmonary hypertension. Trametinib, a MEK-inhibitor approved for treatment of RAS/MAPK-mutated cancers, is an emerging treatment option for HCM in NS. We report a patient with NS and HCM, treated with Trametinib and documented by global RNA sequencing before and during treatment to define transcriptional effects of MEK-inhibition. A preterm infant with HCM carrying the RAF1:p.Ser257Leu variant, rapidly developed severe congestive heart failure (CHF) unresponsive to standard treatments. Trametinib was introduced (0.022 mg/kg/day) with prompt clinical improvement and subsequent amelioration of HCM at ultrasound. The appearance of pulmonary artery aneurysm and pulmonary hypertension contributed to a rapid worsening after ventriculoperitoneal shunt device placement for posthemorrhagic hydrocephalus: she deceased for untreatable CHF at 3 months of age. Autopsy showed severe obstructive HCM, pulmonary artery dilation, disarrayed pulmonary vascular anatomy consistent with pulmonary capillary hemangiomatosis. Transcriptome across treatment, highlighted robust transcriptional changes induced by MEK-inhibition. Our findings highlight a previously unappreciated connection between pulmonary vascular disease and the severe outcome already reported in patients with RAF1-associated NS. While MEK-inhibition appears a promising therapeutic option for HCM in RASopathies, it appears insufficient to revert pulmonary hypertension.

Towards precision medicine in heart failure

The number of therapies for heart failure (HF) with reduced ejection fraction has nearly doubled in the past decade. In addition, new therapies for HF caused by hypertrophic and infiltrative disease are emerging rapidly. Indeed, we are on the verge of a new era in HF in which insights into the biology of myocardial disease can be matched to an understanding of the genetic predisposition in an individual patient to inform precision approaches to therapy. In this Review, we summarize the biology of HF, emphasizing the causal relationships between genetic contributors and traditional structure-based remodelling outcomes, and highlight the mechanisms of action of traditional and novel therapeutics. We discuss the latest advances in our understanding of both the Mendelian genetics of cardiomyopathy and the complex genetics of the clinical syndrome presenting as HF. In the phenotypic domain, we discuss applications of machine learning for the subcategorization of HF in ways that might inform rational prescribing of medications. We aim to bridge the gap between the biology of the failing heart, its diverse clinical presentations and the range of medications that we can now use to treat it. We present a roadmap for the future of precision medicine in HF.

Genotype-cardiac phenotype correlations in a large single-center cohort of patients affected by RASopathies: Clinical implications and literature review

Congenital heart disease (CHD) and hypertrophic cardiomyopathy (HCM) are common features in patients affected by RASopathies. The aim of this study was to assess genotype- phenotype correlations, focusing on the cardiac features and outcomes of interventions for cardiac conditions, in a single-center cohort of 116 patients with molecularly confirmed diagnosis of RASopathy, and compare these findings with previously published data. All enrolled patients underwent a comprehensive echocardiographic examination. Relevant information was also retrospectively collected through the analysis of clinical records. As expected, significant associations were found between PTPN11 mutations and pulmonary stenosis (both valvular and supravalvular) and pulmonary valve dysplasia, and between SOS1 mutations and valvular defects. Similarly, HRAS mutations were significantly associated with HCM. Potential associations between less prevalent mutations and cardiac defects were also observed, including RIT1 mutations and HCM, SOS2 mutations and septal defects, and SHOC2 mutations and septal and valve abnormalities. Patients with PTPN11 mutations were the most likely to require both a primary treatment (transcatheter or surgical) and surgical reintervention. Other cardiac anomalies less reported until recently in this population, such as isolated functional and structural mitral valve diseases, as well as a sigmoid-shaped interventricular septum in the absence of HCM, were also reported. In conclusion, our study confirms previous data but also provides new insights on cardiac involvement in RASopathies. Further research concerning genotype/phenotype associations in RASopathies could lead to a more rational approach to surgery and the consideration of drug therapy in patients at higher risk due to age, severity, anatomy, and comorbidities.

Genotype-phenotype association by echocardiography offers incremental value in patients with Noonan Syndrome with Multiple Lentigines

BACKGROUND

Noonan Syndrome with Multiple Lentigines (NSML) and Noonan Syndrome (NS) can be difficult to differentiate clinically in early childhood. This study aims to describe characteristics of the ventricular septum that may differentiate NSML from NS. We hypothesize that the shape of the ventricular septum determined by echocardiography correlates with genotype and may distinguish patients with NSML from those with NS.

METHODS

We analyzed data from 17 NSML and 67 NS patients. Forty normal and 30 sarcomeric hypertrophic cardiomyopathy (HCM) patients were included as controls. Septal morphology was qualitatively evaluated, and septal angle was measured quantitatively at end diastole. We recorded the presence of a ventricular septal bulge (VSB) and reviewed genetic testing results for each patient.

RESULTS

The most important findings were a sigmoid septum (71%) and VSB (71%) in NSML. NSML septal angle was decreased compared to the normal and sarcomeric HCM control groups, respectively (149 ± 13 vs. 177 ± 3, p < 0.001; 149 ± 13 vs. 172 ± 7, p < 0.001). NS septal angle was similar to the controls (176 ± 6 vs. 177 ± 3, p > 0.5; 176 ± 6 vs. 172 ± 7, p > 0.5). NSML-linked pathogenic variants were associated with sigmoid septum and VSB.

CONCLUSIONS

These findings provide novel phenotypic evidence to clinicians that may offer incremental diagnostic value in counseling families in ambiguous NSML/NS cases.

IMPACT

Characteristics of the ventricular septum are linked to specific gene variants that cause NSML and NS. Sigmoid septum and VSB are associated with NSML. This novel echocardiographic association may help clinicians distinguish NSML from NS in ambiguous cases. Early distinction between the two may be important, as syndrome-specific therapies may become available in the near future. This study may encourage further research into genotype-phenotype associations in other forms of HCM.

Early Outcomes of Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy in Children With Noonan Syndrome

Noonan syndrome (NS) is a genetic syndrome causing obstructive hypertrophic cardiomyopathy (HCM) in infants. Studies of cardiac surgery in pediatric HCM patients with NS (NS-HCM) are lacking. We aim to characterize the early disease course of young NS-HCM patients before adolescence and assess their complications and survival condition after septal myectomy. Pediatric obstructive HCM patients who underwent septal myectomy at age 10 years or under were enrolled consecutively between 2009 and 2019. Ten patients with NS and 43 non-NS patients were enrolled in our study. NS-HCM patients were diagnosed at a younger age (5.00 ± 7.48 months vs. 18.73 ± 26.96 months) and more often had biventricular outflow tract obstruction (90.00% vs 30.23%). The surgical treatment can significantly reduce the pressure gradient of the outflow tract. More NS-HCM patients had biventricular reconstruction (70.00% vs 25.58%). The overall survival rates in all patients were 98.04% during 5-year follow-up, respectively. Complete heart block (CHB) was the most prevalent complication in patients with NS and tended to be more common than in non-NS patients (20% vs 7.32%). No sudden cardiac death (SCD) occurred in CHB patients who had pacemaker implantation. Biventricular reconstruction was the risk factor for CHB. Septal myectomy is safe and effective surgery to relieve obstruction in young age pediatric obstructive NS-HCM patients. Postoperative CHB is a common complication, especially in patients who underwent biventricular reconstruction. The implantation of pacemaker can protect CHB patients from SCD and improve their prognosis.

Atypical cardiac defects in patients with RASopathies: Updated data on CARNET study

BACKGROUND

RASopathies are a set of relatively common autosomal dominant clinically and genetically heterogeneous disorders. Cardiac outcomes in terms of mortality and morbidity for common heart defects (such as pulmonary valve stenosis and hypertrophic cardiomyopathy) have been reported. Nevertheless, also Atypical Cardiac Defects (ACDs) are described. The aim of the present study was to report both prevalence and cardiac outcome of ACDs in patients with RASopathies.

METHODS

A retrospective, multicentric observational study (CArdiac Rasopathy NETwork-CARNET study) was carried out. Clinical, surgical, and genetic data of the patients who were followed until December 2019 were collected.

RESULTS

Forty-five patients out of 440 followed in CARNET centers had ACDs. Noonan Syndrome (NS), NS Multiple Lentigines (NSML) and CardioFacioCutaneous Syndrome (CFCS) were present in 36, 5 and 4 patients, respectively. Median age at last follow-up was 20.1 years (range 6.9-47 years). Different ACDs were reported, including mitral and aortic valve dysfunction, ascending and descending aortic arch anomalies, coronary arteries dilation, enlargement of left atrial appendage and isolated pulmonary branches diseases. Five patients (11%) underwent cardiac surgery and one of them underwent a second intervention for mitral valve replacement and severe pericardial effusion. No patients died in our cohort until December 2019.

CONCLUSIONS

Patients with RASopathies present a distinct CHD spectrum. Present data suggest that also ACDs must be carefully investigated for their possible impact on the clinical outcome. A careful longitudinal follow up until the individuals reach an adult age is recommended.

Hypertrophic Cardiomyopathy in Children: Pathophysiology, Diagnosis, and Treatment of Non-sarcomeric Causes

Hypertrophic cardiomyopathy (HCM) is a myocardial disease characterized by left ventricular hypertrophy not solely explained by abnormal loading conditions. Despite its rare prevalence in pediatric age, HCM carries a relevant risk of mortality and morbidity in both infants and children. Pediatric HCM is a large heterogeneous group of disorders. Other than mutations in sarcomeric genes, which represent the most important cause of HCM in adults, childhood HCM includes a high prevalence of non-sarcomeric causes, including inherited errors of metabolism (i.e., glycogen storage diseases, lysosomal storage diseases, and fatty acid oxidation disorders), malformation syndromes, neuromuscular diseases, and mitochondrial disease, which globally represent up to 35% of children with HCM. The age of presentation and the underlying etiology significantly impact the prognosis of children with HCM. Moreover, in recent years, different targeted approaches for non-sarcomeric etiologies of HCM have emerged. Therefore, the etiological diagnosis is a fundamental step in designing specific management and therapy in these subjects. The present review aims to provide an overview of the non-sarcomeric causes of HCM in children, focusing on the pathophysiology, clinical features, diagnosis, and treatment of these rare disorders.

Cardiomyopathies in children: classification, diagnosis and treatment

PURPOSE OF REVIEW

Cardiomyopathies are rare in the pediatric population, but significantly impact on morbidity and mortality. The present review aims to provide an overview of cardiomyopathies in children and some practical guidelines for their prognostic stratification and management.

RECENT FINDINGS

Pediatric cardiomyopathies may present as isolated cardiac muscle disease or in the context of complex clinical syndromes. The etiologic characterization represents an important step in the diagnosis and treatment of cardiomyopathies because of its impact on prognosis and on therapeutic measures. Indeed, replacement therapy is nowadays widely available and changes the natural history of the disease. More complex is the management of isolated cardiomyopathies, which lack specific therapies, mainly aimed at symptomatic relief. In this context, heart transplantation shows excellent outcomes in children, but wait-list mortality is still very high. Device therapy for sudden cardiac death prevention and the use of mechanical assist devices are becoming more common in the clinical practice and may help to reduce mortality.

SUMMARY

Providing insight into pediatric cardiomyopathies classification helps in the prognostication and management of such diseases. Recent years witnessed a significant improvement in mortality, but future research is still needed to improve quality of life and life expectations in the pediatric population.

Quantitative analysis of proteins which are members of the same protein complex but cause locus heterogeneity in disease

It is still largely unknown how mutations in different genes cause similar diseases – a condition known as locus heterogeneity. A likely explanation is that the different proteins encoded by the locus heterogeneity genes participate in the same biological function and, specifically, that they belong to the same protein complex. Here we report that, in up to 30% of the instances of locus heterogeneity, the disease-causing proteins are indeed members of the same protein complex. Moreover, we observed that, in many instances, the diseases and protein complexes only partially intersect. Among the possible explanations, we surmised that some genes that encode proteins in the complex have not yet been reported as causing disease and are therefore candidate disease genes. Mutations of known human disease genes and murine orthologs of candidate disease genes that encode proteins in the same protein complex do in fact often cause similar phenotypes in humans and mice. Furthermore, we found that the disease-complex intersection is not only incomplete but also non-univocal, with many examples of one disease intersecting more than one protein complex or one protein complex intersecting more than one disease. These limits notwithstanding, this study shows that action on proteins in the same complex is a widespread pathogenic mechanism underlying numerous instances of locus heterogeneity.

Mitochondrial functions and rare diseases

Mitochondria are dynamic cellular organelles responsible for a large variety of biochemical processes as energy transduction, REDOX signaling, the biosynthesis of hormones and vitamins, inflammation or cell death execution. Cell biology studies established that 1158 human genes encode proteins localized to mitochondria, as registered in MITOCARTA. Clinical studies showed that a large number of these mitochondrial proteins can be altered in expression and function through genetic, epigenetic or biochemical mechanisms including the interaction with environmental toxics or iatrogenic medicine. As a result, pathogenic mitochondrial genetic and functional defects participate to the onset and the progression of a growing number of rare diseases. In this review we provide an exhaustive survey of the biochemical, genetic and clinical studies that demonstrated the implication of mitochondrial dysfunction in human rare diseases. We discuss the striking diversity of the symptoms caused by mitochondrial dysfunction and the strategies proposed for mitochondrial therapy, including a survey of ongoing clinical trials.

Long-term outcomes of childhood onset Noonan compared to sarcomere hypertrophic cardiomyopathy

Background

To compare outcome and cardiac pathology between patients with Noonan syndrome (N-HCM) and sarcomere protein-associated (S-HCM) childhood onset hypertrophic cardiomyopathy (HCM).

Methods

Clinical data were recorded from medical charts. Primary endpoint was survival. Secondary endpoints were survival without hospitalization, without intervention or without arrhythmic events. Functional clinical status and results from genetic testing, imaging, electrocardiographic (ECG) studies, cardiopulmonary exercise testing (CPET) and histopathology were compared between groups.

Results

Childhood HCM was diagnosed in 29 N-HCM and 34 S-HCM patients. Follow-up time was greater than 10 years in more than half of all patients. Mortality was below 7% and not different between groups. Children with N-HCM presented at a younger age and there was less time of survival without hospitalization for heart failure or intervention in N-HCM compared to S-HCM patients. Clinical functional status improved over time in N-HCM patients. On long-term follow-up, left ventricular posterior wall thickness indexed to body surface area decreased in N-HCM and increased in S-HCM patients. There was a trend to lower risk for severe arrhythmic events in N-HCM patients and only S-HCM individuals received an implantable cardioverter-defibrillator. There were no differences between groups in ventricular function, ECG and CPET parameters. Myocardial fibrosis as assessed by histopathology of myocardial specimens and cardiovascular magnetic resonance with late gadolinium enhancement or T1 mapping was present in both groups.

Conclusions

When compared to S-HCM patients, children with N-HCM have increased morbidity during early disease course, but favorable long-term outcome with low mortality, stagnation of myocardial hypertrophy, and low risk for malignant arrhythmias.

SOS1 mutations in Noonan syndrome: Cardiomyopathies and not only congenital heart defects! Report of six patients including two novel variants and literature review

Noonan syndrome (NS) is caused by mutations in more than 10 genes, mainly PTPN11, SOS1, RAF1, and RIT1. Congenital heart defects and cardiomyopathy (CMP) are associated with significant morbidity and mortality in NS. Although hypertrophic CMP has "classically" been reported in association to RAF1, RIT1, and PTPN11 variants, SOS1 appears to be poorly related to CMP. Patients with NS attending our Center from January 2013 to June 2018 were eligible for inclusion if they carried SOS1 variants and presented with-or developed-CMP. Literature review describing the co-existence of SOS1 mutation and CMP was also performed. We identified six patients with SOS1 variants and CMP (male to female ratio 2:1) including two novel variants. CMP spectrum encompassed: (a) dilated CMP, (b) nonobstructive hypertrophic CMPs, and (c) obstructive hypertrophic CMPs. Survival is 100%. Literature review included 16 SOS1 mutated in CMP. CMP, mainly hypertrophic, has been often reported in association to RAF1, RIT1, and PTPN11 variants. Differently from previous reports, due to the frequent association of SOS1 variants and CMP in our single center experience, we suggest potential underestimated proportion of SOS1 in pediatric CMPs.

Clinical and functional characterization of a novel RASopathy-causing SHOC2 mutation associated with prenatal-onset hypertrophic cardiomyopathy

SHOC2 is a scaffold protein mediating RAS-promoted activation of mitogen-activated protein kinase (MAPK) signaling in response to extracellular stimuli. A recurrent activating mutation in SHOC2 (p.Ser2Gly) causes Mazzanti syndrome, a RASopathy characterized by features resembling Noonan syndrome and distinctive ectodermal abnormalities. A second mutation (p.Met173Ile) supposed to cause loss-of-function was more recently identified in two individuals with milder phenotypes. Here, we report on the third RASopathy-causing SHOC2 mutation (c.807_808delinsTT, p.Gln269_His270delinsHisTyr), which was found associated with prenatal-onset hypertrophic cardiomyopathy. Structural analyses indicated a possible impact of the mutation on the relative orientation of the two SHOC2's leucine-rich repeat domains. Functional studies provided evidence of its activating role, revealing enhanced binding of the mutant protein to MRAS and PPP1CB, and increased signaling through the MAPK cascade. Differing from SHOC2 ^S2G , SHOC2 ^{Q269_H270delinsHY} is not constitutively targeted to the plasma membrane. These data document that diverse mechanisms in SHOC2 functional dysregulation converge toward MAPK signaling upregulation.

A severe clinical phenotype of Noonan syndrome with neonatal hypertrophic cardiomyopathy in the second case worldwide with RAF1 S259Y neomutation

Noonan syndrome and related disorders are a group of clinically and genetically heterogeneous conditions caused by mutations in genes of the RAS/MAPK pathway. Noonan syndrome causes multiple congenital anomalies, which are frequently accompanied by hypertrophic cardiomyopathy (HCM). We report here a Tunisian patient with a severe phenotype of Noonan syndrome including neonatal HCM, facial dysmorphism, severe failure to thrive, cutaneous abnormalities, pectus excavatum and severe stunted growth, who died in her eighth month of life. Using whole exome sequencing, we identified a de novo mutation in exon 7 of the RAF1 gene: c.776C > A (p.Ser259Tyr). This mutation affects a highly conserved serine residue, a main mediator of Raf-1 inhibition via phosphorylation. To our knowledge the c.776C > A mutation has been previously reported in only one case with prenatally diagnosed Noonan syndrome. Our study further supports the striking correlation of RAF1 mutations with HCM and highlights the clinical severity of Noonan syndrome associated with a RAF1 p.Ser259Tyr mutation.

The spectrum of genetic variants and phenotypic features of Southeast Asian patients with Noonan syndrome

Background

Noonan syndrome (NS) is an autosomal dominant disorder that belongs to a group of developmental disorders called RASopathies with overlapping features and multiple causative genes. The aim of the study was to identify mutations underlying this disorder in patients from Southeast Asia and characterize their clinical presentations.

Methods

Patients were identified from the hospital's Genetics clinics after assessment by attending clinical geneticists. A targeted gene panel was used for next‐generation sequencing on genomic DNA extracted from the blood samples of 17 patients.

Results

Heterozygous missense variants were identified in 13 patients: eight were in PTPN11, three in SOS1, and one each in RIT1 and KRAS. All are known variants that have been reported in patients with NS. Of the 13 patients with identified variants, 10 had short stature, the most common feature for NS. Four of the eight patients with PTPN11 variants had atrial septal defect. Only two had pulmonary stenosis which is reported to be common for PTPN11 mutation carriers. Another two had hypertrophic cardiomyopathy, a feature which is negatively associated with PTPN11 mutations.

Conclusions

Our study provides the mutation and phenotypic spectrum of NS from a new population group. The molecular testing yield of 76% is similar to other studies and shows that the targeted panel approach is useful for identifying genetic mutations in NS which has multiple causative genes. The molecular basis for the phenotypes of the remaining patients remains unknown and would need to be uncovered via sequencing of additional genes or other investigative methods.

Cardiovascular disease in Noonan syndrome

PURPOSE OF REVIEW

To provide information on the scope of cardiac disease in Noonan syndrome.

RECENT FINDINGS

Noonan syndrome is a common autosomal dominant RASopathy disorder characterized by clinical findings of facial dysmorphism, congenital heart disease, and short stature. The degree of genetic heterogeneity has recently become evident in that Noonan syndrome is now known to be caused by mutations in a large variety of genes which produce dysregulation of the RAS-MAPK (mitogen-activated protein kinase) signaling pathway. The scope of cardiac disease in Noonan syndrome is quite variable depending on the gene mutation, with some mutations usually associated with a high incidence of congenital heart defects (PTPN11, KRAS, and others) while those with predominantly hypertrophic cardiomyopathy (HCM) have higher risk and morbidity profiles (RAF1, RIT1, and those associated with multiple lentigines).

SUMMARY

Cardiac disease in Noonan syndrome varies according to the type of gene mutation. The most common forms of cardiac disease include pulmonary stenosis, HCM, and atrial septal defect. HCM in general is associated with increased risk, mortality, and morbidity. New concepts for potential treatments are discussed.