A clinical study of Noonan syndrome

Severe generalized edema in a premature neonate: A case report and literature review

Key Clinical Message

With no family history, and an atypical phenotype, the clinical diagnosing of Noonan syndrome (NS) can be very difficult. The present case emphasized that generalized edema in neonates may be the potential first symptom of NS.

Abstract

Severe generalized edema is a rare pathological condition with high mortality in newborns, in particular the premature infants. It is characterized by the extensive subcutaneous tissue edema and the accumulation of fluid in neonatal body fluid compartments. The etiology and pathogenesis of hydrops in neonates are quite complex. Generally speaking, hydrops can be divided into immune hydrops and non-immune hydrops according to the etiology. It is still challenging in treating severe neonatal edema. In this study, we presented a preterm newborn with severe generalized edema after birth, which was finally diagnosed with Noonan syndrome (NS). The infant clinically manifested as severe generalized edema alone, without the involvement of multiple organ malformation. Generalized edema in neonates was probably the first symptom of NS. Therefore, differential diagnosis of NS is necessary for infants developing generalized edema.

Developmental effect of RASopathy mutations on neuronal network activity on a chip

RASopathies are a group of genetic disorders caused by mutations in genes encoding components and regulators of the RAS/MAPK signaling pathway, resulting in overactivation of signaling. RASopathy patients exhibit distinctive facial features, cardiopathies, growth and skeletal abnormalities, and varying degrees of neurocognitive impairments including neurodevelopmental delay, intellectual disabilities, or attention deficits. At present, it is unclear how RASopathy mutations cause neurocognitive impairment and what their neuron-specific cellular and network phenotypes are. Here, we investigated the effect of RASopathy mutations on the establishment and functional maturation of neuronal networks. We isolated cortical neurons from RASopathy mouse models, cultured them on multielectrode arrays and performed longitudinal recordings of spontaneous activity in developing networks as well as recordings of evoked responses in mature neurons. To facilitate the analysis of large and complex data sets resulting from long-term multielectrode recordings, we developed MATLAB-based tools for data processing, analysis, and statistical evaluation. Longitudinal analysis of spontaneous network activity revealed a convergent developmental phenotype in neurons carrying the gain-of-function Noonan syndrome-related mutations Ptpn11 D61Y and Kras V14l. The phenotype was more pronounced at the earlier time points and faded out over time, suggesting the emergence of compensatory mechanisms during network maturation. Nevertheless, persistent differences in excitatory/inhibitory balance and network excitability were observed in mature networks. This study improves the understanding of the complex relationship between genetic mutations and clinical manifestations in RASopathies by adding insights into functional network processes as an additional piece of the puzzle.

Epilepsy in Legius syndrome: Coincidence or causation?

Legius syndrome is a rare genetic disorder, caused by heterozygous SPRED1 pathogenic variants, which shares phenotypic features with neurofibromatosis type 1 (NF1). Both conditions typically involve café-au-lait macules, axillary freckling, and macrocephaly; however, patients with NF1 are also at risk for tumors, such as optic nerve gliomas and neurofibromas. Seizure risk is known to be elevated in NF1, but there has been little study of this aspect of Legius syndrome. The reported epilepsy incidence is 3.3%-5%, well above the general population incidence of ~0.5%-1%, but the few reports in the literature have very little data regarding epilepsy phenotype. We identified two unrelated individuals, both with Legius syndrome and epilepsy, and performed thorough phenotyping. One individual's mother also had Legius syndrome and now-resolved childhood epilepsy, as well as reports of more distant relatives who also had multiple café-au-lait macules and seizures. Both probands had experienced childhood-onset focal seizures, with normal brain MRI. In one patient, EEG later showed apparently generalized epileptiform abnormalities. Based on the data from this small case series and literature review, seizure risk is increased in people with Legius syndrome, but the epilepsy prognosis appears to be generally good, with patients having either self-limited or pharmacoresponsive courses.

Gonadal dysfunction in a man with Noonan syndrome from the LZTR1 variant: case report and review of literature

Noonan syndrome (NS) is a genetic disorder characterized by multiple congenital defects caused by mutations in the RAS/mitogen-activated protein kinase pathway. Male fertility has been reported to be impaired in NS, but only a few studies have focused on fertility status in NS patients and underlying mechanisms are still incompletely understood. We describe the case of a 35-year-old man who underwent an andrological evaluation due to erectile dysfunction and severe oligospermia. A syndromic facial appearance and reduced testis size were present on clinical examination. Hormonal evaluation showed normal total testosterone level, high FSH level, and low-normal AMH and inhibin B, compatible with primary Sertoli cell dysfunction. Genetic analysis demonstrated the pathogenetic heterozygous variant c.742G>A, p.(Gly248Arg) of the LZTR1 gene (NM_006767.3). This case report provides increased knowledge on primary gonadal dysfunction in men with NS and enriches the clinical spectrum of NS from a rare variant in the novel gene LZTR1.

Undiagnosed RASopathies in infertile men

RASopathies are syndromes caused by congenital defects in the Ras/mitogen-activated protein kinase (MAPK) pathway genes, with a population prevalence of 1 in 1,000. Patients are typically identified in childhood based on diverse characteristic features, including cryptorchidism (CR) in >50% of affected men. As CR predisposes to spermatogenic failure (SPGF; total sperm count per ejaculate 0-39 million), we hypothesized that men seeking infertility management include cases with undiagnosed RASopathies. Likely pathogenic or pathogenic (LP/P) variants in 22 RASopathy-linked genes were screened in 521 idiopathic SPGF patients (including 155 CR cases) and 323 normozoospermic controls using exome sequencing. All 844 men were recruited to the ESTonian ANDrology (ESTAND) cohort and underwent identical andrological phenotyping. RASopathy-specific variant interpretation guidelines were used for pathogenicity assessment. LP/P variants were identified in PTPN11 (two), SOS1 (three), SOS2 (one), LZTR1 (one), SPRED1 (one), NF1 (one), and MAP2K1 (one). The findings affected six of 155 cases with CR and SPGF, three of 366 men with SPGF only, and one (of 323) normozoospermic subfertile man. The subgroup "CR and SPGF" had over 13-fold enrichment of findings compared to controls (3.9% vs. 0.3%; Fisher's exact test, p = 5.5 × 10-3). All ESTAND subjects with LP/P variants in the Ras/MAPK pathway genes presented congenital genitourinary anomalies, skeletal and joint conditions, and other RASopathy-linked health concerns. Rare forms of malignancies (schwannomatosis and pancreatic and testicular cancer) were reported on four occasions. The Genetics of Male Infertility Initiative (GEMINI) cohort (1,416 SPGF cases and 317 fertile men) was used to validate the outcome. LP/P variants in PTPN11 (three), LZTR1 (three), and MRAS (one) were identified in six SPGF cases (including 4/31 GEMINI cases with CR) and one normozoospermic man. Undiagnosed RASopathies were detected in total for 17 ESTAND and GEMINI subjects, 15 SPGF patients (10 with CR), and two fertile men. Affected RASopathy genes showed high expression in spermatogenic and testicular somatic cells. In conclusion, congenital defects in the Ras/MAPK pathway genes represent a new congenital etiology of syndromic male infertility. Undiagnosed RASopathies were especially enriched among patients with a history of cryptorchidism. Given the relationship between RASopathies and other conditions, infertile men found to have this molecular diagnosis should be evaluated for known RASopathy-linked health concerns, including specific rare malignancies.

Clinical Variability in a Family with Noonan Syndrome with a Homozygous PTPN11 Gene Variant in Two Individuals

Objective

Noonan syndrome (NS) is characterized by dysmorphic facial features, short stature, congenital heart defects, and varying levels of developmental delays. It is a genetic, multisystem disorder with autosomal dominant inheritance and is the most common of the RASopathies. In approximately 50% of patients, NS is caused by variants in the Protein Tyrosine Phosphatase Non-Receptor Type 11 (PTPN11) gene. The aim of this study was to evaluate two patients with a previously reported PTPN11 homozygous variant for the first time and seven other kindred members carrying the same heterozygous variant in terms of clinical, biochemical, genetic, and response to treatment.

Methods

Nine patients diagnosed with NS due to the same variants in the PTPN11 gene were included in the study.

Results

The median (range) age at diagnosis was 11.5 (6.8-13.9) years and the mean follow-up duration was 4.7 (1-7.6) years. In eight patients (88.9%), short stature was present. The height standard deviation score of the patients on admission was -3.24±1.15. In six of the patients, growth hormone treatment was initiated. Cardiovascular or bleeding disorders were not detected in any of the patients. Three (33.3%) had hearing loss, two (22.2%) had ocular findings and one (11.1%) had a horseshoe kidney. The mean psychomotor development performance score was 84.03±17.09 and the verbal score was 82.88±9.42. Genetic analysis revealed a variant in the PTPN11 gene [c.772G>A; (p.Glu258Lys)] that had been previously described and was detected in all patients. Two patients were homozygous for this variant and short stature was more severe in these two.

Conclusion

A previously described in PTPN11 affected nine members of the same kindred, two with homozygous inheritance and the remainder being heterozygous. To the best of our knowledge, these are the first homozygous PTPN11 case reports published, coming from two related consanguineous families.

The most important problems and needs of rasopathy patients with a noonan syndrome spectrum disorder

BACKGROUND

Noonan syndrome spectrum disorders (NSSDs) constitute a group within the Rasopathies, and are one of the largest groups of syndromes with impact on multi-organ involvement known. The extreme variability of the clinical phenotype is, among others, due to the numerous different genes that are involved, and the differences in clinical presentation over the life span. We have studied the needs of patients and their relatives aiming to develop, evaluate and choose focus in research, medical care and policy to better meet their perspectives.

METHODS

Using the participatory and interactive Dialogue method, 80 patients and relatives mentioned 53 different problems or needs (topics) that were categorized into eight themes. These themes and the topics within each theme, were subsequently prioritized by putting them in order of importance methodologically.

RESULTS

The four highest prioritized themes were: (1) Physical problems (non-musculoskeletal related); (2) Social, emotional and behavioral problems; (3) Cognitive functioning and information processing; and (4) Problems related to the musculoskeletal system. Nineteen out of the 53 topics were physical problems. According to the total group of respondents, the top 3 prioritized topics within theme 1 were coagulation problems, heart problems, and feeding problems. Also data stratified by age groups, phenotype (NS and other NSSDs) and gender showed some remarkable results. For instance, feeding problems were prioritized as the most important topic of the highest prioritized theme, according to patients aged 0-12 years. Also feeding problems show a significant difference in its prioritization according to female patients (2) compared to male patients (7). On the other hand, heart problems were not mentioned in the top three prioritized topics in the youngest age groups, although heart problems are generally considered most important for patients with NSSD.

CONCLUSIONS

With our results we underline the importance of methodologically inventorying the needs of NSSD patients, not only at the group level, but to also focus on specific needs according to e.g. age, phenotype and gender. For instance, it is remarkable that both the current Clinical Guidelines and the Noonan Syndrome diagnostic criteria give little to no attention to feeding problems, though our results indicate that, to the youngest patients, these problems have top priority. A similar situation appears to apply to the clinical management of e.g. coagulation, neuropsychological and musculoskeletal problems (like physiotherapy or occupational therapy) and to a need for (educational) tools to support patients at school or at work. Our study may help to shape targeted (clinical) management, research and policy inside and outside medical (research) institutes and shed light on the complex phenotypes of NSSDs, the families' and patients' perspectives on the everyday consequences of the many different problems, as well as their needs.

New insights on Noonan syndrome's clinical phenotype: a single center retrospective study

BACKGROUND

Noonan syndrome (NS) is a clinically and genetically heterogeneous disorder. Since its clinical phenotype is often mild and difficult to differentiate from other syndromes, its diagnosis can be challenging and its prevalence in the pediatric population is most certainly underestimated. The difficulty in identifying Noonan syndrome is also increased by the fact that genetic tests are currently not able to detect an underlying mutation in around 10% of the cases.

METHODS

This is a retrospective, observational study conducted at the Institute for Maternal and Child "Burlo Garofolo" in Trieste, Italy. We recruited all the patients with clinical and/or genetic diagnosis of NS who were evaluated at the Department of Pediatrics between October 2015 and October 2020. Statistical analyses were performed with IBM SPSS Statistics software. The association between discrete variables has been evaluated through chi-squared test, indicating statistically significant p with Pearson test or Fischer test for variables less than 5.

RESULTS

We recruited a total of 35 patients affected by Noonan syndrome. In 24 patients (75%) we identified an underlying genetic substrate: 17 patients had a mutation on PTPN11 (61%), 2 in SOS1, KRAS and SHOC2 (7% each) and only 1 in RAF1 (4%). 25% of the subjects did not receive a genetic confirm. As for the phenotype of the syndrome, our study identified the presence of some clinical features which were previously unrelated or poorly related to NS. For example, renal and central nervous system abnormalities were found at a higher rate compared to the current literature. On the contrary, some features that are considered very suggestive of NS (such as lymphatic abnormalities and the classical facial features) were not frequently found in our population.

CONCLUSIONS

In our analysis, we focused on the main phenotypic features of NS, identifying various clinical manifestation that were not associated with this genetic condition before. This could be helpful in raising the knowledge of NS's clinical spectrum, facilitating its diagnosis.

Noonan syndrome: improving recognition and diagnosis

Noonan syndrome (NS) is a mostly dominantly inherited disorder affecting 1:1000 to 1:2500 live births. The phenotype varies in severity and can involve multiple organ systems over a patient's lifetime. Diagnosis is based on a combination of features, including typical facial features, short stature, skeletal abnormalities, presence of cardiac defects, mild developmental delay, cryptorchidism, lymphatic dysplasia and a family history of NS. The phenotype varies from oligosymptomatic adults without significant medical issues to severely affected neonates with life-threatening heart disease. Early, accurate diagnosis is important for individualised management and to optimise developmental and long-term outcomes, but mildly affected patients often go undiagnosed for both healthcare provider (HCP)-related and patient-related reasons. Lack of awareness of NS among HCPs means that some do not recognise the condition, particularly in mildly affected patients and families. Some families do not want to receive a diagnosis that medicalises a condition that may account for family traits (eg, distinctive facial features and short stature), particularly when a child's physical and cognitive development may be satisfactory. As for any condition with lifelong effects on multiple organ systems, a multidisciplinary approach provides the best care. It is proposed that increasing awareness of NS among non-specialist HCPs and other professionals could help direct a parent/carer to seek specialist advice and increase the number of NS diagnoses, with the potential to optimise lifelong patient outcomes. Non-specialists do not need to become experts in either diagnosis or treatment; however, early recognition of NS and referral to an appropriate specialist is important.

Management of nutritional and gastrointestinal issues in RASopathies: A narrative review

Noonan, Costello, and cardio-facio-cutaneous syndrome are neurodevelopmental disorders belonging to the RASopathies, a group of syndromes caused by alterations in the RAS/MAPK pathway. They are characterized by similar clinical features, among which feeding difficulties, growth delay, and gastro-intestinal disorders are frequent, causing pain and discomfort in patients. Hereby, we describe the main nutritional and gastrointestinal issues reported in individuals with RASopathies, specifically in Noonan syndrome, Noonan syndrome-related disorders, Costello, and cardio-facio-cutaneous syndromes. Fifty percent of children with Noonan syndrome may experience feeding difficulties that usually have a spontaneous resolution by the second year of life, especially associated to genes different than PTPN11 and SOS1. More severe manifestations often require artificial enteral nutrition in infancy are observed in Costello syndrome, mostly associated to c.34G>A substitution in the HRAS gene. In cardio-facio-cutaneous syndrome feeding issues are usually present (90-100% of cases), especially in individuals carrying variants in BRAF, MAP2K1, and MAP2K2 genes, and artificial enteral intervention, even after scholar age, may be required. Moreover, disorders associated with gastrointestinal dysmotility as gastro-esophageal reflux and constipation are commonly reported in all the above-mentioned syndromes. Given the impact on growth and on the quality of life of these patients, early evaluation and prompt personalized management plans are fundamental.

Prevalence of gastrointestinal disorders in individuals with RASopathies: May RAS/MAP/ERK pathway dysfunctions be a model of neuropathic pain and visceral hypersensitivity?

RASopathies are a group of neurodevelopmental syndromes caused by germline variants in genes of the Ras/MAP/ERK pathway. Growth failure, neurological involvement, and pain represent the main features of these conditions. ERK signaling cascade plays a crucial role in nociception and visceral pain and it is likely implicated in the genesis of neuropathic pain and maintenance of altered pain states. We studied the prevalence of abdominal pain and functional gastrointestinal (GI) disorders in a large sample of individuals with RASopathies. A brief pain inventory questionnaire and semi-structured dedicated interview were used to investigate presence and localization of pain. A Rome IV questionnaire was used to screen for functional GI disorders. Eighty patients with clinical and molecular diagnoses of RASopathy were recruited (42 with Noonan syndrome; 17 with Costello Syndrome and 21 with cardio-facio-cutaneous syndrome). Overall, the prevalence of abdominal pain was 44% and prevalence of functional GI disorders was 78% with constipation, abdominal pain, and aerophagia being the most frequently detected ones. A significant association was found between pain and irritable bowel syndrome, functional constipation and aerophagia. Children with RASopathies have a high prevalence of functional gastrointestinal disorders. These children could represent a good in vivo model to study neuropathic pain, visceral hypersensitivity and gut-brain axis disorders.

Inside the Noonan "universe": Literature review on growth, GH/IGF axis and rhGH treatment: Facts and concerns

Noonan syndrome (NS) is a disorder characterized by a typical facial gestalt, congenital heart defects, variable cognitive deficits, skeletal defects, and short stature. NS is caused by germline pathogenic variants in genes coding proteins with a role in the RAS/mitogen-activated protein kinase signaling pathway, and it is typically associated with substantial genetic and clinical complexity and variability. Short stature is a cardinal feature in NS, with evidence indicating that growth hormone (GH) deficiency, partial GH insensitivity, and altered response to insulin-like growth factor I (IGF-1) are contributing events for growth failure in these patients. Decreased IGF-I, together with low/normal responses to GH pharmacological provocation tests, indicating a variable presence of GH deficiency/resistance, in particular in subjects with pathogenic PTPN11 variants, are frequently reported. Nonetheless, short- and long-term studies have demonstrated a consistent and significant increase in height velocity (HV) in NS children and adolescents treated with recombinant human GH (rhGH). While the overall experience with rhGH treatment in NS patients with short stature is reassuring, it is difficult to systematically compare published data due to heterogeneous protocols, potential enrolment bias, the small size of cohorts in many studies, different cohort selection criteria and varying durations of therapy. Furthermore, in most studies, the genetic information is lacking. NS is associated with a higher risk of benign and malignant proliferative disorders and hypertrophic cardiomyopathy, and rhGH treatment may further increase risk in these patients, especially as dosages vary widely. Herein we provide an updated review of aspects related to growth, altered function of the GH/IGF axis and cell response to GH/IGF stimulation, rhGH treatment and its possible adverse events. Given the clinical variability and genetic heterogeneity of NS, treatment with rhGH should be personalized and a conservative approach with judicious surveillance is recommended. Depending on the genotype, an individualized follow-up and close monitoring during rhGH treatments, also focusing on screening for neoplasms, should be considered.

Epilepsy in a cohort of children with Noonan syndrome and related disorders

Noonan syndrome (NS) and related disorders encompass a phenotypically heterogeneous group of conditions due to mutations in the Ras/Mitogen-activated protein kinase pathway. The main objective of this study was to assess the presence and characteristics of epilepsy in children and adolescents affected by NS and related disorders. The study included all the patients aged 5-21 years who had been diagnosed with NS or of one of three Noonan-like syndromes (i.e., cardio-facio-cutaneous syndrome, Noonan syndrome with multiple lentigines, and Noonan-like syndrome with loose anagen hair) at a university pediatric hospital. Clinical, EEGs, brain MRIs, and genotype data were extracted from the medical records, and follow-up telephone interviews were conducted to obtain updated information about epilepsy and its course. Out of a total of 75 patients (38 [50.7%] males, median age at assessment 12.0 years [q1 9.0-q3 17.0]; 61 [81.3%] with NS; and 14 [18.7%] with a Noonan-like syndrome), 13 (17.3%) had epilepsy, with median age at onset of 4.0 years (q1 2.0-q3 8.0, min 0.1-max 17.0). Epilepsy was more common among Noonan-like patients (50.0%) than in NS (9.8%, p < 0.001), and its presence was associated with neurodevelopmental delay (p < 0.001, OR 14.6 95% CI 3.6-59.4), cognitive impairment (p = 0.002, OR 11.2 95% CI 2.5-51.0), need for educational support (p < 0.001, OR 21.8, 95% CI 2.6-179.1), and lower adaptive functioning (median [q1-q3]: 54.0 [q1 40.0-q3 77.5] vs 97.0 [q1 76.5-q3 107.0] of the non-epileptic subgroup, p = 0.004). In 10 out of 13 cases (76.9%), the epilepsy outcome was good (i.e., seizure-free for more than 12 months with or without anti-seizure medication).

CONCLUSION

Epilepsy was more common in NS than reported in the general population, with a significantly higher rate in Noonan-like syndromes. Epilepsy was associated with neurodevelopmental delay, cognitive impairment, and lower adaptive functioning.

WHAT IS KNOWN

• Neurological abnormalities have been reported in NS and related disorders. • There is evidence of a phenotype-genotype relationship for neurological abnormalities.

WHAT IS NEW

• Epilepsy was found to be more common in NS and related disorders than typically reported in the general population and associated with neurodevelopmental delay, cognitive, and functional impairment. • The Noonan-like phenotype had a higher frequency of epilepsy than typical NS.

Neurological impairment in children with acute liver failure following liver transplantation-A single-center experience

BACKGROUND

Although overall survival of ALF has improved, neurological restoration after recovery from ALF may not always be satisfactory. The purpose of this study was to investigate the occurrence and possible causes of NI in children with ALF following LT.

METHODS

We retrospectively examined all children younger than 16 years old with ALF who subsequently underwent LT at our center between January 2005 and December 2016. NI was assessed in December 2016 using the six-point Pediatric Cerebral Performance Category score and was defined as any increase in the score.

RESULTS

There were 62 children with median age 10 months (quartile range 5-34). The etiology of ALF was indeterminate in 47 children (75.8%). The median duration from admission to LT was 5.5 days (quartile range 4-7), and 96.8% (60/62) received living donor LT. The overall survival was 83.9% (52/62) in a median follow-up period of 4.2 years. Mild-to-moderate NI was observed in 23.1% (12/52) of the survivors. Possible causes of NI were underlying systemic disease (n = 3), perioperative brain lesion (n = 2), and unclassified (n = 7). All seven patients with unclassified NI were less than 12 months old. The unclassified NI causes were presumed to be ALF, its perioperative care, and the vulnerable infant brain.

CONCLUSIONS

NI in children with ALF following LT was not rare and should be prevented. Further investigations are required to clarify the characteristics of the patients with unclassified NI.

Delayed Puberty Phenotype Observed in Noonan Syndrome Is More Pronounced in Girls than Boys

INTRODUCTION

Pubertal delay is described as one of the clinical features in Noonan syndrome (NS) and it may be one of the factors causing short adult height in those patients. The present study aimed at characterizing pubertal development in NS and identifying pubertal delay predictors.

METHODS

We analyzed 133 individuals with a molecular diagnosis of NS and clinical puberty evaluation. We characterized delayed puberty as pubertal onset after 12 years in girls and 13.5 years in boys, according to parameters of the Brazilian population. To investigate its predictors, we correlated the age at onset of puberty with several characteristics and genotype in a multilevel regression model. For comprehending pubertal development in NS, we assessed age and anthropometric measures at each Tanner stage and adult age.

RESULTS

The mean age at puberty onset for girls was 11.9 ± 1.9 years and for boys, 12.5 ± 1.7 years, significantly later than the Brazilian population (p = 0.025; p < 0.001). Girls (49.1%) presented delayed puberty more frequently than boys (27.9%, p = 0.031). Body mass index standard deviation scores (SDS) and insulin growth factor 1 SDS at puberty onset significantly predicted later puberty entry. Height gain from the onset of puberty to adult height was lower in children with pubertal delay.

CONCLUSION

Pubertal delay is characteristically found in children with NS, more frequently in females. The low weight of patients with NS could modulate the age of puberty, just as the increase in overweight/obesity in the general population has shown an effect on reducing the age of onset of puberty.

Gonadal function in Noonan syndrome

Noonan syndrome (NS) is a relatively common developmental disorder characterised by the association of craniofacial abnormalities, congenital heart defects, short stature and skeletal abnormalities, variable developmental delay/learning disability, and predisposition to certain cancers. NS is caused by germline mutations in genes encoding components or regulators of the RAS/mitogen-activated protein kinase (MAPK) signaling pathway. Although abnormalities in the hypothalamic-pituitary-gonadal axis have long been reported in NS patients, there is only scarce published data on this subject. Puberty is usually delayed of about two years for both boys and girls with NS. However, in the majority of patients, it starts spontaneously suggesting a normal hypothalamic-pituitary input. The lower fat mass usually observed in NS patients may influence the timing of puberty. Although there is almost no reliable data on this issue, it is usually considered that fertility is not affected in NS females. In contrast, primary testicular insufficiency, predominant on Sertoli cell function, is reported in NS males. However, the exact frequency of infertility in adult males is unknown. More generally, although the features of NS are well described during childhood, little is known about the progression of the disease in adulthood. Prospective long-term follow-up studies are required to further investigate gonadal function and fertility in NS adults and to clarify the long-term follow-up of these patients.

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.

Refractory thrombocytopenia could be a rare initial presentation of Noonan syndrome in newborn infants: a case report and literature review

Background

Noonan syndrome (NS) is a relatively rare inherited disease. Typical clinical presentation is important for the diagnosis of NS. But the initial presentation of NS could be significant variant individually which results in the difficult of working diagnosis. Here we report a rare neonatal case of NS who presented with refractory thrombocytopenia as the initial manifestation.

Case presentation

This was a preterm infant with refractory thrombocytopenia of unknown origin transferred from obstetric hospital at 6 weeks of age. During hospitalization, typical phenotypes of NS in addition to thrombocytopenia were observed, such as typical facial characteristics, short stature, atrial septal defect, cryptochidism, coagulation defect and chylothorax. Genetic testing showed a pathogenic variant at exon 2 of the PTPN11 gene with c.124A > G (p.T42A). Respiratory distress was deteriorated with progressive chylothorax. Chest tube was inserted for continuous draining. Chemical pleurodesis with erythromycin was tried twice, but barely effective. Finally, parents decided to withdraw medical care and the patient died.

Conclusions

Thrombocytopenia could be the first symptom of Noonan syndrome. After ruling out other common causes of thrombocytopenia, NS should be considered as the working diagnosis.

Cochlear Implantation in Noonan Syndrome With and Without Multiple Lentigines: A Case Report and Systematic Review

Objectives

To describe outcomes after bilateral cochlear implantation (CI) in a patient with a pathologic PTPN11 variant associated with Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML). Additionally, to assess the utility of CI in this specific population based on our outcome and previous reports.

Study Design

Retrospective case report with literature review using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

Patients

A young boy with various multiorgan abnormalities, speech and language delay, and persistent hearing loss who was found to have a heterozygous PTPN11 gene mutation at age 2.

Interventions

Bilateral tympanostomy tube placement, diagnostic imaging, and eventual staged bilateral CI.

Main Outcome Measures

Objective audiometric testing and developmental milestone attainment.

Results

Bilateral CI was successfully completed over a 2-month period. The patient illustrated significant improvement in objective audiologic measurement. However, he continues to sign as his main form of communication without significant speech progression.

Conclusions

Early diagnostic and therapeutic intervention in patients with NS/NSML can help improve long-term audiologic and speech development. Given the heterogeneity of NS/NSML, a multidisciplinary approach is needed for optimal outcomes.

The RASopathies: Biology, genetics and therapeutic options

The RASopathies are a group of genetic diseases in which the Ras/MAPK signaling pathway is inappropriately activated as a result of mutations in genes encoding proteins within this pathway. As their causative mutations have been identified, this group of diseases has expanded to include neurofibromatosis type 1 (NF1), Legius syndrome, Noonan syndrome, CBL syndrome, Noonan syndrome-like disorder with loose anagen hair, Noonan syndrome with multiple lentigines, Costello syndrome, cardiofaciocutaneous syndrome, gingival fibromatosis and capillary malformation-arteriovenous malformation syndrome. Many of these genetic disorders share clinical features in common such as abnormal facies, short stature, varying degrees of cognitive impairment, cardiovascular abnormalities, skeletal abnormalities and a predisposition to develop benign and malignant neoplasms. Others are more dissimilar, even though their mutations are in the same gene that is mutated in a different RASopathy. Here, we describe the clinical features of each RASopathy and contrast them with the other RASopathies. We discuss the genetics of these disorders, including the causative mutations for each RASopathy, the impact that these mutations have on the function of an individual protein and how this dysregulates the Ras/MAPK signaling pathway. As several of these individual disorders are genetically heterogeneous, we also consider the different genes that can be mutated to produce disease with the same phenotype. We also discuss how our growing understanding of dysregulated Ras/MAPK signaling had led to the development of new therapeutic agents and what work will be critically important in the future to improve the lives of patients with RASopathies.

Feeding Problems in Patients with Noonan Syndrome: A Narrative Review

Noonan syndrome (NS) belongs to the group of Noonan syndrome spectrum disorders (NSSD), which is a group of phenotypically related conditions. Feeding problems are often present not only in infancy but also in childhood, and even beyond that period. We describe the different aspects of feeding problems using a (theoretical) concept proposed in 2019. More than 50% of infants with NS develop feeding problems, and up to half of these infants will be tube-dependent for some time. Although, in general, there is a major improvement between the age of 1 and 2 years, with only a minority still having feeding problems after the age of 2 years, as long as the feeding problems continue, the impact on the quality of life of both NS infants and their caregivers may be significant. Feeding problems in general improve faster in children with a pathogenic PTPN11 or SOS1 variant. The mechanism of the feeding problems is complex, and may be due to medical causes (gastroesophageal reflux disease and delayed gastric emptying, cardiac disease and infections), feeding-skill dysfunction, nutritional dysfunction with increased energy demand, or primary or secondary psychosocial dysfunction. Many of the underlying mechanisms are still unknown. The treatment of the feeding problems may be a medical challenge, especially when the feeding problems are accompanied by feeding-skill dysfunction and psychosocial dysfunction. This warrants a multidisciplinary intervention including psychology, nutrition, medicine, speech language pathology and occupational therapy.

Methemoglobinemia Induced by Prilocaine in a Child With Noonan Syndrome

Limited information is currently available on methemoglobinemia caused by the administration of prilocaine in children undergoing dental procedures in Japan. This case report presents the development of methemoglobinemia due to prilocaine overdose. The patient was a female aged 5 years 8 months with Noonan syndrome who also had pulmonary valve stenosis and hypertrophic cardiomyopathy. She presented with severe dental caries affecting 12 total teeth and required general anesthesia due to a lack of cooperation during dental treatment. General anesthesia was performed, during which 3% prilocaine with 0.03 IU/mL felypressin was administered intraoperatively via infiltration. Her SpO2 gradually decreased after 30 minutes, and cyanosis was observed postoperatively. Several assessments including a 12-lead electrocardiogram, an anteroposterior chest radiograph, and venous blood gas analysis were performed to identify potential causes. However, there were no indications of acute respiratory or cardiovascular abnormalities. It was noted that a total of 192 mg prilocaine was administered during the procedure, and methemoglobinemia was suspected to have developed because of overdose. Further testing revealed an elevated serum methemoglobin of 6.9%, supporting methemoglobinemia as the cause of her decreased SpO2. In dental procedures that require the use of prilocaine to treat multiple teeth, particularly for pediatric patients, it is important to carefully manage prilocaine dosing, as an overdose may lead to methemoglobinemia.

Genetic conditions of short stature: A review of three classic examples

Noonan, Turner, and Prader-Willi syndromes are classical genetic disorders that are marked by short stature. Each disorder has been recognized for several decades and is backed by extensive published literature describing its features, genetic origins, and optimal treatment strategies. These disorders are accompanied by a multitude of comorbidities, including cardiovascular issues, endocrinopathies, and infertility. Diagnostic delays, syndrome-associated comorbidities, and inefficient communication among the members of a patient's health care team can affect a patient's well-being from birth through adulthood. Insufficient information is available to help patients and their multidisciplinary team of providers transition from pediatric to adult health care systems. The aim of this review is to summarize the clinical features and genetics associated with each syndrome, describe best practices for diagnosis and treatment, and emphasize the importance of multidisciplinary teams and appropriate care plans for the pediatric to adult health care transition.

Dose-dependent seizure control with MEK inhibitor therapy for progressive glioma in a child with neurofibromatosis type 1

BACKGROUND

Low-grade gliomas (LGGs) occurring in children can result in many different neurologic complications, including seizures. MEK inhibitors are increasingly being used to treat LGG, but their effect on associated neurologic symptoms has not been established.

RESULTS

Here, we report a patient with neurofibromatosis type 1 (NF1), medically refractory epilepsy (MRE), and an extensive optic pathway glioma (OPG) who developed dose-dependent seizure control while being treated with selumetinib. Seizure frequency rebounded after dose reduction for cardiac toxicity, then improved, and finally ceased after restarting full dosing, allowing confidence in the cause of improvement.

CONCLUSION

Selumetinib may have promise in epilepsy management in other children with NF1 or LGG.

Endocrine system involvement in patients with RASopathies: A case series

BACKGROUND AND OBJECTIVES

Endocrine complications have been described in patients affected by RASopathies but no systematic assessment has been reported. In this study, we investigate the prevalence of endocrine disorders in a consecutive unselected cohort of patients with RASopathies.

STUDY DESIGN

72 patients with a genetically confirmed RASopathy (Noonan syndrome [NS], N=53; 29 LEOPARD syndrome [LS], N=2; cardiofaciocutaneous syndrome [CFCS], N=14; subjects showing co-occurring pathogenic variants in PTPN11 and NF1, N=3) and an age- and sex-matched healthy controls were included in the study. Endocrine system involvement was investigated by assessing the thyroid function, pubertal development, auxological parameters, adrenal function and bone metabolism.

RESULTS

Short stature was detected in 40% and 64% of the NS and CFCS subcohorts, respectively. Patients showed lower Z-scores at DXA than controls (p<0.05) when considering the entire case load and both NS and CFCS groups. Vitamin D and Calcitonin levels were significantly lower (p< 0.01), Parathormone levels significantly higher (p<0.05) in patients compared to the control group (p<0.05). Patients with lower BMD showed reduced physical activity and joint pain. Finally, anti-TPO antibody levels were significantly higher in patients than in controls when considering the entire case load and both NS and CFCS groups.

CONCLUSIONS

The collected data demonstrate a high prevalence of thyroid autoimmunity, confirming an increased risk to develop autoimmune disorders both in NS and CFCS. Reduced BMD, probably associated to reduced physical activity and inflammatory cytokines, also occurs. These findings are expected to have implications for the follow-up and prevention of osteopenia/osteoporosis in both NS and CFCS.

Management of growth failure and other endocrine aspects in patients with Noonan syndrome across Europe: A sub-analysis of a European clinical practice survey

AIM

To date, there is a lack of international guidelines regarding the management of the endocrine features of individuals with Noonan syndrome (NS). The aim was to develop a clinical practice survey to gather information on current treatment and management of these patients across Europe.

MATERIALS AND METHODS

A group of 10 experts from three clinical specialities involved in the management of NS patients (clinical geneticists, paediatric endocrinologists, and paediatric cardiologists) developed a 60-question clinical practice survey. The questionnaire was implemented in Survey Monkey and sent to physicians from these three specialities via European/national societies. Contingency tables and the Chi-Squared test for independence were used to examine differences between specialities and countries.

RESULTS

In total, responses of 364 specialists (paediatric endocrinologists, 40%; geneticists, 30%; paediatric cardiologists, 30%) from 20 European countries were analysed. While endocrinologists mostly referred to national growth charts for the general population, geneticists mostly referred to NS-specific growth charts. Approximately half of the endocrinologists perform growth hormone (GH) stimulation tests in short patients with low IGF1 levels. Two thirds of endocrinologists begin GH treatment for short patients in early childhood (4-6.9 years), and over half of them selected a threshold of -2 standard deviation score (SDS) according to national growth charts. The main concerns about GH treatment appear to be presence of hypertrophic cardiomyopathy (HCM) (59%), increased risk of malignancy (46%), and limited efficacy (31%). When asked if they consider HCM as a contraindication for GH treatment, one third of respondents skipped this question, and among those who replied, two thirds selected 'cannot answer', suggesting a high level of uncertainty. A total of 21 adverse cardiac responses to GH treatment were reported. Although most respondents had not encountered any malignancy during GH treatment, six malignancies were reported. Finally, about half of the endocrinologists expected a typical final height gain of 1-1.5 SDS with GH treatment.

CONCLUSION

This survey describes for the first time the current clinical practice of endocrine aspects of NS across Europe and helps us to identify gaps in the management but also in the knowledge of this genetic disorder.

RASopathies and hemostatic abnormalities: key role of platelet dysfunction

Background

Bleeding anomalies have been reported in patients affected by Noonan syndrome. No study has been performed in patients with molecularly confirmed RASopathy. We aimed to characterize the frequency and types of bleeding disorders in patients with RASopathies and evaluate any significant association with laboratory findings.

Patients and methods

Forty-nine individuals (PTPN11, n = 27; SOS1, n = 7; RIT1, n = 3; SPRED1, n = 1; LZTR1, N = 3; RAF1, n = 2; BRAF, n = 4; MEK1, n = 1; MEK2, n = 1), and 49 age- and sex-matched controls were enrolled. The “Paediatric Bleeding Questionnaire Scoring Key” was administered to patients and families. Laboratory screening tests including clotting factors dosing, platelet count, Prothrombin Time and Partial Thromboplastin Time, were employed both in patients and controls to characterize the bleeding diathesis. A subgroup of 29/49 patients and 29/49 controls was also tested for platelet function.

Results

Regardless of the gene involved, pathological paediatric bleeding scores were recorded in 14/49 (28.5%) patients. Indeed, 7 were mutated in PTPN11, 3 in SOS1, 2 in RIT1, 1 in BRAF, and 1 in MEK1. Compared to patients with normal bleeding scores, those with pathologic bleeding score showed higher prevalence of splenomegaly (p = 0.006), prolonged aPTT (p = 0.04), lower levels of coagulation factor V (FV, p = 0.001), FVII (p = 0.003), FX (p = 0.0008) and FXIII (p = 0.002), higher vWAg (p = 0.04), and lower platelet sensitivity to Ristocetin (p = 0.001), arachidonic acid (AA) (p = 0.009) and collagen (p = 0.01). The presence of hematomas inversely correlated with factor V (p = 0.002), factor VII (p = 0.003), factor X (p = 0.002) and factor XIII (p = 0.004) levels, and directly correlated with platelet response to collagen (p = 0.02) and AA (p = 0.01). The presence of splenomegaly directly correlated with the presence of hematoma (p = 0.006), platelet response to Ristocetin (p = 0.04) and AA (p = 0.04), and inversely correlated with factor V levels (p = 0.03).

Conclusions

Patients with RASopathies and a bleeding tendency exhibit multiple laboratory abnormalities, including platelet-related disorders. Splenomegaly is frequently detected and might be a suggestive sign for qualitative platelet dysfunction. A comprehensive clinical assessment should be carried out at diagnosis, during the follow-up and before any surgical procedures. Since there is currently no consensus on management of bleeding complications, it is important that physicians closely monitor these patients.

RASopathies: The musculoskeletal consequences and their etiology and pathogenesis

The RASopathies comprise an ever-growing number of clinical syndromes resulting from germline mutations in components of the RAS/MAPK signaling pathway. While multiple organs and tissues may be affected by these mutations, this review will focus on how these mutations specifically impact the musculoskeletal system. Herein, we review the genetics and musculoskeletal phenotypes of these syndromes in humans. We discuss how mutations in the RASopathy syndromes have been studied in translational mouse models. Finally, we discuss how signaling molecules within the RAS/MAPK pathway are involved in normal and abnormal bone biology in the context of osteoblasts, osteoclasts and chondrocytes.

European Medical Education Initiative on Noonan syndrome: A clinical practice survey assessing the diagnosis and clinical management of individuals with Noonan syndrome across Europe

INTRODUCTION

Noonan syndrome (NS) is a rare genetic disorder caused by mutations in genes encoding components of the RAS/mitogen-activated protein kinase (MAPK) signalling pathway. Patients with NS exhibit certain characteristic features, including cardiac defects, short stature, distinctive facial appearance, skeletal abnormalities, cognitive deficits, and predisposition to certain cancers. Here, a clinical practice survey was developed to learn more about differences in the diagnosis and management of this disease across Europe. The aim was to identify gaps in the knowledge and management of this rare disorder.

MATERIALS AND METHODS

The European Medical Education Initiative on NS, which comprised a group of 10 experts, developed a 60-question clinical practice survey to gather information from European physicians on the diagnosis and clinical management of patients with diseases in the NS phenotypic spectrum. Physicians from three specialities (clinical genetics, paediatric endocrinology, paediatric cardiology) were invited to complete the survey by several national and European societies. Differences in answers provided by respondents between specialities and countries were analysed using contingency tables and the Chi-Squared test for independence. The Friedman's test was used for related samples.

RESULTS

Data were analysed from 364 respondents from 20 European countries. Most respondents came from France (21%), Spain (18%), Germany (16%), Italy (15%), United Kingdom (8%) and the Czech Republic (6%). Respondents were distributed evenly across three specialities: clinical genetics (30%), paediatric endocrinology (40%) and paediatric cardiology (30%). Care practices were generally aligned across the countries participating in the survey. Delayed diagnosis did not emerge as a critical issue, but certain unmet needs were identified, including transition of young patients to adult medical services and awareness of family support groups.

CONCLUSION

Data collected from this survey provide a comprehensive summary of the diagnosis and clinical management practices for patients with NS across different European countries.

Regulation of the Small GTPase Ras and Its Relevance to Human Disease

Ras research has experienced a considerable boost in recent years, not least prompted by the Ras initiative launched by the NCI in 2013 ( https://www.cancer.gov/research/key-initiatives/ras ), accompanied and conditioned by a strongly reinvigorated determination within the Ras community to develop therapeutics attacking directly the Ras oncoproteins. As a member of the small G-protein superfamily, function and transforming activity of Ras all revolve about its GDP/GTP loading status. For one thing, the extent of GTP loading will determine the proportion of active Ras in the cell, with implications for intensity and quality of downstream signaling. But also the rate of nucleotide exchange, i.e., the Ras-GDP/GTP cycling rate, can have a major impact on Ras function, as illustrated perhaps most impressively by newly discovered fast-cycling oncogenic mutants of the Ras-related GTPase Rac1. Thus, while the last years have witnessed memorable new findings and technical developments in the Ras field, leading to an improved insight into many aspects of Ras biology, they have not jolted at the basics, but rather deepened our view of the fundamental regulatory principles of Ras activity control. In this brief review, we revisit the role and mechanisms of Ras nucleotide loading and its implications for cancer in the light of recent findings.

Etiology and Treatment of Growth Delay in Noonan Syndrome

Noonan syndrome is characterized by multiple phenotypic features, including growth retardation, which represents the main cause of consultation to the clinician. Longitudinal growth during childhood and adolescence depends on several factors, among them an intact somatotrophic axis, which is characterized by an adequate growth hormone (GH) secretion by the pituitary, subsequent binding to its receptor, proper function of the post-receptor signaling pathway for this hormone (JAK-STAT5b and RAS/MAPK), and ultimately by the production of its main effector, insulin like growth factor 1 (IGF-1). Several studies regarding the function of the somatotrophic axis in patients with Noonan syndrome and data from murine models, suggest that partial GH insensitivity at a post-receptor level, as well as possible derangements in the RAS/MAPK pathway, are the most likely causes for the growth failure in these patients. Treatment with recombinant human growth hormone (rhGH) has been used extensively to promote linear growth in these patients. Numerous treatment protocols have been employed so far, but the published studies are quite heterogeneous regarding patient selection, length of treatment, and dose of rhGH utilized, so the true benefit of GH therapy is somewhat difficult to establish. This review will discuss the possible etiologies for the growth delay, as well as the outcomes following rhGH treatment in patients with Noonan syndrome.

Prolonged thrombocytopenia in a neonate with Noonan syndrome: a case report

We report a case of a Chinese neonate who was diagnosed with Noonan syndrome and had persistent, self-limited thrombocytopenia. The neonate was admitted to the Neonatology Department 20 minutes after birth because of respiratory distress. From birth until 2 months of age, platelet values fluctuated between approximately 6 and 30 × 10⁹/L. There was no intracranial hemorrhage. However, the child had a transient hypocalcemic seizure and fever. We excluded thrombocytopenia caused by perinatal asphyxia, immune thrombocytopenia, fetomaternal alloimmune thrombocytopenia, juvenile myelomonocytic leukemia, and chromosome 13, 18, and 21 trisomy syndromes. Despite treatment with anti-infective agents and transfusion of platelets and immunoglobulin, the platelet count did not return to the normal range. Genetic testing confirmed a PTPN11 gene mutation, which led to the diagnosis of Noonan syndrome. At 3 months of age, the platelet count gradually increased without intervention and returned to the normal range by 6 months. We speculate that the thrombocytopenia in this case was closely related to Noonan syndrome.

Objective differential diagnosis of Noonan and Williams-Beuren syndromes in diverse populations using quantitative facial phenotyping

Introduction

Patients with Noonan and Williams–Beuren syndrome present similar facial phenotypes modulated by their ethnic background. Although distinctive facial features have been reported, studies show a variable incidence of those characteristics in populations with diverse ancestry. Hence, a differential diagnosis based on reported facial features can be challenging. Although accurate diagnoses are possible with genetic testing, they are not available in developing and remote regions.

Methods

We used a facial analysis technology to identify the most discriminative facial metrics between 286 patients with Noonan and 161 with Williams‐Beuren syndrome with diverse ethnic background. We quantified the most discriminative metrics, and their ranges both globally and in different ethnic groups. We also created population‐based appearance images that are useful not only as clinical references but also for training purposes. Finally, we trained both global and ethnic‐specific machine learning models with previous metrics to distinguish between patients with Noonan and Williams–Beuren syndromes.

Results

We obtained a classification accuracy of 85.68% in the global population evaluated using cross‐validation, which improved to 90.38% when we adapted the facial metrics to the ethnicity of the patients (p = 0.024).

Conclusion

Our facial analysis provided for the first time quantitative reference facial metrics for the differential diagnosis Noonan and Williams–Beuren syndromes in diverse populations.

Manic and Depressive Symptoms in Children Diagnosed with Noonan Syndrome

Noonan syndrome (NS) is a dominant clinically variable and genetically heterogeneous developmental disorder caused by germ-line mutations encoding components of the Ras–MAPK signaling pathway. A few studies have investigated psychopathological features occurring in individuals with NS, although they were poorly analyzed. The aim of the present work is to investigate the psychopathological features in children and adolescents with NS focusing on depressive and hypo-manic symptoms. Thirty-seven subjects with molecularly confirmed diagnosis were systematically evaluated through a psychopathological assessment. In addition, an evaluation of the cognitive level was performed. Our analyses showed a high recurrence of attention deficit and hyperactivity disorder symptoms, emotional dysregulation, irritability, and anxiety symptomatology. The mean cognitive level was on the average. The present study provides new relevant information on psychopathological features in individuals with NS. The implications for clinicians are discussed including the monitoring of mood disorders in a clinical evolution.

Noonan syndrome patient-specific induced cardiomyocyte model carrying SOS1 gene variant c.1654A>G

Noonan syndrome (NS) is a dominant autosomal genetic disorder, associated with mutations in several genes that exhibit multisystem abnormal development including cardiac defects. NS associated with the Son of Sevenless homolog 1 (SOS1) gene mutation attributes to the development of cardiomyopathy and congenital heart defects. Since the treatment option for NS is very limited, an in vitro disease model with SOS1 gene mutation would be beneficial for exploring therapeutic possibilities for NS. We reprogrammed cardiac fibroblasts obtained from a NS patient and normal control skin fibroblasts (C-SF) into induced pluripotent stem cells (iPSCs). We identified NS-iPSCs carry a heterozygous single nucleotide variation in the SOS1 gene at the c.1654A > G. Furthermore, the control and NS-iPSCs were differentiated into induced cardiomyocytes (iCMCs), and the electron microscopic analysis showed that the sarcomeres of the NS-iCMCs were highly disorganized. FACS analysis showed that 47.5% of the NS-iCMCs co-expressed GATA4 and cardiac troponin T proteins, and the mRNA expression levels of many cardiac related genes, studied by qRT-PCR array, were significantly reduced when compared to the control C-iCMCs. We report for the first time that NS-iPSCs carry a single nucleotide variation in the SOS1 gene at the c.1654A>G were showing significantly reduced cardiac genes and proteins expression as well as structurally and functionally compromised when compared to C-iCMCs. These iPSCs and iCMCs can be used as a modeling platform to unravel the pathologic mechanisms and also the development of novel drug for the cardiomyopathy in patients with NS.

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.

A genotype-first approach to exploring Mendelian cardiovascular traits with clear external manifestations

Purpose:

The purpose of this study is to use a genotype-first approach to explore highly penetrant, autosomal dominant cardiovascular diseases with external features, the RASopathies and Marfan syndrome (MFS), using biobank data.

Methods:

This study uses exome sequencing and corresponding phenotypic data from Mount Sinai’s BioMe (n = 32,344) and the United Kingdom Biobank (UKBB; n = 49,960). Variant curation identified pathogenic/likely pathogenic (P/LP) variants in RASopathy genes and FBN1.

Results:

Twenty-one subjects harbored P/LP RASopathy variants; three (14%) were diagnosed, and another 46% had ≥1 classic Noonan syndrome (NS) feature. Major NS features (short stature (9.5% p = 7e-5) and heart anomalies (19%, p < 1e-5)) were less frequent than expected. Prevalence of hypothyroidism/autoimmune disorders was enriched compared to biobank populations (p = 0.007). For subjects with FBN1 P/LP variants, 14/41 (34%) had a MFS diagnosis or highly suggestive features. 5/15 participants (33%) with echocardiographic data had aortic dilation, fewer than expected (p=8e-6). Ectopia lentis affected only 15% (p < 1e-5).

Conclusions:

Substantial fractions of individuals harboring P/LP variants with partial or full phenotypic matches to a RASopathy or MFS remain undiagnosed, some not meeting diagnostic criteria. Routine population genotyping would enable multi-disciplinary care and avoid life-threatening events.

Haploinsufficiency of RREB1 causes a Noonan-like RASopathy via epigenetic reprogramming of RAS-MAPK pathway genes

RAS-MAPK signaling mediates processes critical to normal development including cell proliferation, survival, and differentiation. Germline mutation of RAS-MAPK genes lead to the Noonan-spectrum of syndromes. Here, we present a patient affected by a 6p-interstitial microdeletion with unknown underlying molecular etiology. Examination of 6p-interstitial microdeletion cases reveals shared clinical features consistent with Noonan-spectrum disorders including short stature, facial dysmorphia and cardiovascular abnormalities. We find the RAS-responsive element binding protein-1 (RREB1) is the common deleted gene in multiple 6p-interstitial microdeletion cases. Rreb1 hemizygous mice display orbital hypertelorism and cardiac hypertrophy phenocopying the human syndrome. Rreb1 haploinsufficiency leads to sensitization of MAPK signaling. Rreb1 recruits Sin3a and Kdm1a to control H3K4 methylation at MAPK pathway gene promoters. Haploinsufficiency of SIN3A and mutations in KDM1A cause syndromes similar to RREB1 haploinsufficiency suggesting genetic perturbation of the RREB1-SIN3A-KDM1A complex represents a new category of RASopathy-like syndromes arising through epigenetic reprogramming of MAPK pathway genes.

A case of Myhre syndrome mimicking juvenile scleroderma

BACKGROUND

Myhre syndrome is a genetic disorder caused by gain of function mutations in the SMAD Family Member 4 (SMAD4) gene, resulting in progressive, proliferative skin and organ fibrosis. Skin thickening and joint contractures are often the main presenting features of the disease and may be mistaken for juvenile scleroderma.

CASE PRESENTATION

We report a case of a 13 year-old female presenting with widespread skin thickening and joint contractures from infancy. She was diagnosed with diffuse cutaneous systemic sclerosis, and treatment with corticosteroids and subcutaneous methotrexate recommended. There was however disease progression prompting genetic testing. This identified a rare heterozygous pathogenic variant c.1499 T > C (p.Ile500Thr) in the SMAD4 gene, suggesting a diagnosis of Myhre syndrome. Securing a molecular diagnosis in this case allowed the cessation of immunosuppression, thus reducing the burden of unnecessary and potentially harmful treatment, and allowing genetic counselling.

CONCLUSION

Myhre Syndrome is a rare genetic mimic of scleroderma that should be considered alongside several other monogenic diseases presenting with pathological fibrosis from early in life. We highlight this case to provide an overview of these genetic mimics of scleroderma, and highlight the molecular pathways that can lead to pathological fibrosis. This may provide clues to the pathogenesis of sporadic juvenile scleroderma, and could suggest novel therapeutic targets.

Noonan Syndrome in 12 -Year-Old Male: Case Report and Orthodontic Management of the Occlusion

Background/Aim: Noonan syndrome (NS) is an autosomal dominant disorder, caused by mutations on genes located on the long arm of chromosome 12. The condition has no sex or race predilection and its incidence is 1 per 1,000 – 2,500 live births. Individuals affected with Noonan syndrome have distinctive facial features, hypertelorism, short stature, congenital heart disease; mainly pulmonary stenosis and hypertrophic cardiomyopathy, chest deformities, variable learning disabilities and mental retardation. Orofacial findings in Noonan syndrome may be high-arched palate, micrognathia, dental malocclusion and articulation difficulties.

Case report: The present article reports on a male case of 12 years old, referred for treatment in the orthodontic office. Despite the difficulties of hyperactivity, the light mental delay and the gag reflex, the treatment was completed satisfactorily with fixed orthodontic appliances in 15 months. Both the patient and his parents were happy with the results. The patient is presently undergoing the retention period of this orthodontic treatment.

Conclusions: Despite the difficulties of treating a child with a genetic syndrome for his/her malocclusion, the reported case presented in this article proves that it is always worth trying for the benefit of the patient.

Noonan syndrome with somnambulism: A rare case report

Noonan syndrome is an autosomal dominant, genetic, multisystem disorder with a prevalence of 1 in 1000-2500 live births. Characteristic features of the condition include distinctive myopathic facial features, hypertelorism, short and broad nose, webbed neck, and low set ears. About 10% of the subjects have auditory defects due to sensorineural hearing loss. The patient also has short stature, chest deformity (superior pectus carinatum and inferior pectus excavatum), widely spaced nipples, and delayed puberty. A rare psychiatric manifestation of somnambulism and somniloquy in a case of Noonan syndrome is reported.

[Noonan syndrome: genetic and clinical update and treatment options]

Noonan syndrome (NS) is a relatively common genetic condition characterised by short stature, congenital heart defects, and distinctive facial features. NS and other clinically overlapping conditions such as NS with multiple lentigines (formerly called LEOPARD syndrome), cardiofaciocutaneous syndrome, or Costello syndrome, are caused by mutations in genes encoding proteins of the RAS-MAPKinases pathway. Because of this shared mechanism, these conditions have been collectively termed «RASopathies». Despite the recent advances in molecular genetics, nearly 20% of patients still lack a genetic cause, and diagnosis is still made mainly on clinical grounds. NS is a clinically and genetically heterogeneous condition, with variable expressivity and a changing phenotype with age, and affects multiple organs and systems. Therefore, it is essential that physicians involved in the care of these patients are familiarised with their manifestations and the management recommendations, including management of growth and development. Data on growth hormone treatment efficacy are sparse, and show a modest response in height gains, similar to that observed in Turner syndrome. The role of RAS/MAPK hyper-activation in the pathophysiology of this group of disorders offers a unique opportunity for the development of targeted approaches.

Catalytic dysregulation of SHP2 leading to Noonan syndromes affects platelet signaling and functions

Src homology 2 domain-containing phosphatase 2 (SHP2), encoded by the PTPN11 gene, is a ubiquitous protein tyrosine phosphatase that is a critical regulator of signal transduction. Germ line mutations in the PTPN11 gene responsible for catalytic gain or loss of function of SHP2 cause 2 disorders with multiple organ defects: Noonan syndrome (NS) and NS with multiple lentigines (NSML), respectively. Bleeding anomalies have been frequently reported in NS, but causes remain unclear. This study investigates platelet activation in patients with NS and NSML and in 2 mouse models carrying PTPN11 mutations responsible for these 2 syndromes. Platelets from NS mice and patients displayed a significant reduction in aggregation induced by low concentrations of GPVI and CLEC-2 agonists and a decrease in thrombus growth on a collagen surface under arterial shear stress. This was associated with deficiencies in GPVI and αIIbβ3 integrin signaling, platelet secretion, and thromboxane A2 generation. Similarly, arterial thrombus formation was significantly reduced in response to a local carotid injury in NS mice, associated with a significant increase in tail bleeding time. In contrast, NSML mouse platelets exhibited increased platelet activation after GPVI and CLEC-2 stimulation and enhanced platelet thrombotic phenotype on collagen matrix under shear stress. Blood samples from NSML patients also showed a shear stress-dependent elevation of platelet responses on collagen matrix. This study brings new insights into the understanding of SHP2 function in platelets, points to new thrombopathies linked to platelet signaling defects, and provides important information for the medical care of patients with NS in situations involving risk of bleeding.

Autoimmune Thyroid Disease in Specific Genetic Syndromes in Childhood and Adolescence

Autoimmune thyroid disease (ATD) is the most frequent cause of acquired thyroid dysfunction, most commonly presenting either as Hashimoto's thyroiditis or Graves' Disease. Hashimoto's thyroiditis is characterized by the presence of thyroid-specific autoantibodies, more commonly anti-thyroperoxidase antibodies in the serum and the typical inhomogeneous echostructure of the thyroid on a thyroid ultrasound examination. Hashimoto's thyroiditis can for a long time be accompanied by normal thyroid function and hypothyroidism can only progressively be established. Graves' disease is much less frequent in childhood and adolescence and presents with overt hyperthyroidism. After the onset of puberty, ATD affects females with a higher incidence than males, while during the prepubertal period there is not such a clear preponderance of affected females. ATD can occur either isolated or in the context of other autoimmune disorders, such as type 1 Diabetes mellitus (T1D), celiac disease, alopecia areata, vitiligo, etc. Especially at the pediatric age, a higher incidence of ATD is also observed in the context of specific genetic syndromes, such as trisomy 21 (Down syndrome), Klinefelter syndrome, Turner syndrome, or 22q11.2 deletion syndrome. Nevertheless, although thyroid dysfunction may also be observed in other genetic syndromes, such as Prader-Willi or Williams syndrome, the thyroid dysfunction in these syndromes is not the result of thyroid autoimmunity. Interestingly, there is emerging evidence supporting a possible link between autoimmunity and RASopathies. In this review article the incidence, as well as the clinical manifestation and accompanied pathologies of ATD in specific genetic syndromes will be presented and regular follow-up for the early identification of the disorder will be proposed.

Autism Spectrum Disorder Symptom Profile Across the RASopathies

Dysregulation of the Ras MAPK signaling pathway is implicated in the pathogenesis of autism spectrum disorder (ASD). The RASopathies, a group of disorders caused by mutations of the Ras/MAPK pathway genes, share many overlapping clinical features. Studies suggest a high prevalence of ASD in the RASopathies, but detailed characterization of the ASD profile is lacking. The aim of this study was to compare the ASD symptom profile of three distinct RASopathies associated with both gain-of-function and loss-of-function mutations: neurofibromatosis type 1 (NF1), Noonan syndrome (NS), and cardiofaciocutaneous syndrome (CFC). Participants were drawn from existing databases if they had a diagnosis of a RASopathy, met the criteria for ASD, and were able to communicate verbally. We compared the phenotypic profile of NF1 + ASD (n = 48), NS + ASD (n = 11), and CFC + ASD (n = 7) on the Autism Diagnostic Inventory (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS). We found subtle but non-significant group differences with higher levels of social impairments and lower restricted repetitive behaviors in the NF1 group as compared with the NS and CFC groups. We observed group differences in developmental milestones with most severe delays in CFC, followed by NS and NF1. Our results suggest that despite developmental differences, the ASD profile remains relatively consistent across the three RASopathies. Though our results need confirmation in larger samples, they suggest the possibility that treatment and mechanistic insights developed in the context of one RASopathy may be generalizable to others and possibly to non-syndromic ASD associated with dysregulation of Ras/MAPK pathway genes.

Young children with Noonan syndrome: evaluation of feeding problems

Noonan syndrome (NS) is a common genetic syndrome with a high variety in phenotype. Even though genetic testing is possible, NS is still a clinical diagnosis. Feeding problems are often present in infancy. We investigated the feeding status of 108 patients with clinically and genetically confirmed NS. Only patients with a documented feeding status before the age of 6 were included. A distinction was made between patients with early onset feeding problems (< 1 year) and children with late onset feeding problems (> 1 year). Seventy-one of 108 patients had feeding problems, of which 40 patients required tube feeding. Children with a genetic mutation other than PTPN11 and SOS1 had significantly more feeding problems in the first year. Fifty-two of all 108 patients experienced early onset feeding problems, of which 33 required tube feeding. A strong decrease in prevalence of feeding problems was found after the first year of life. Fifteen children developed feeding problems later in life, of which 7 required tube feeding.Conclusion: Feeding problems occur frequently in children with NS, especially in children with NS based on genetic mutations other than PTPN11 and SOS1. Feeding problems develop most often in infancy and decrease with age. What is Known: • Young children with Noonan syndrome may have transient feeding problems. • Most of them will need tube feeding. What is New: • This is the first study of feeding problems in patients with clinically and genetically proven Noonan syndrome. • Feeding problems most often develop in infancy and resolve between the age of 1 and 2.

MRAS Variants Cause Cardiomyocyte Hypertrophy in Patient-Specific Induced Pluripotent Stem Cell-Derived Cardiomyocytes: Additional Evidence for MRAS as a Definitive Noonan Syndrome-Susceptibility Gene

BACKGROUND

MRAS was identified recently as a novel Noonan syndrome (NS)-susceptibility gene. Phenotypically, both patients with NS, harboring pathogenic MRAS variants, displayed severe cardiac hypertrophy. This study aimed to demonstrate both the necessity and sufficiency of a patient-specific variant (p.Gly23Val-MRAS) to cause NS through the generation and characterization of patient-specific, isogenic control, and disease modeled induced pluripotent stem cell (iPSC) lines.

METHODS

iPSCs were derived from a patient with a p.Gly23Val-MRAS variant to assess the effect of MRAS variants on pathogenesis of NS-associated cardiac hypertrophy. CRISPR/Cas9 gene editing was used to correct the pathogenic p.Gly23Val-MRAS variant in patient cells (isogenic control) and to introduce the pathogenic variant into unrelated control cells (disease modeled) to determine the necessity and sufficiency of the p.Gly23Val-MRAS variant to elicit the disease phenotype in iPSC-derived cardiomyocytes (iPSC-CMs). iPSC-CMs were analyzed by microscopy and immunofluroesence, single-cell RNAseq, Western blot, room temperature-quantitative polymerase chain reaction, and live-cell calcium imaging to define an in vitro phenotype of MRAS-mediated cardiac hypertrophy.

RESULTS

Compared with controls, both patient and disease modeled iPSC-CMs were significantly larger and demonstrated changes in gene expression and intracellular pathway signaling characteristic of cardiac hypertrophy. Additionally, patient and disease modeled iPSC-CMs displayed impaired Ca²⁺ handling, including increased frequency of irregular Ca²⁺ transients and changes in Ca²⁺ handling kinetics.

CONCLUSIONS

p.Gly23Val-MRAS is both necessary and sufficient to elicit a cardiac hypertrophy phenotype in iPSC-CMs that includes increased cell size, changes in cardiac gene expression, and abnormal calcium handling-providing further evidence to establish the monogenetic pathogenicity of p.Gly23Val-MRAS in NS with cardiac hypertrophy.