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Noonan Syndrome with Multiple Lentigines (NSML-formerly known as LEOPARD syndrome) is a rare autosomal dominant condition that usually exhibits cardiac involvement with hypertrophic cardiomyopathy (HCM). Here we present a case of a NSML patient with an unusual and patchy cardiac hypertrophy distribution., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Background: We aimed to examine clinical features and outcomes of consecutive molecularly characterized patients with Noonan syndrome with multiple lentigines and hypertrophic cardiomyopathy., Methods: A retrospective, longitudinal multicenter cohort of consecutive children and adults with a genetic diagnosis of Noonan syndrome with multiple lentigines and hypertrophic cardiomyopathy between 2002 and 2019 was assembled. We defined a priori 3 different patterns of left ventricular remodeling during follow-up: (1) an increase in ≥15% of the maximal left ventricular wall thickness (MLVWT), both in mm and z -score (progression); (2) a reduction ≥15% of the MLVWT, both in mm and z -score (absolute regression); (3) a reduction ≥15% of the MLVWT z -score with a stable MLVWT in mm (relative regression). The primary study end point was a composite of cardiovascular death, heart transplantation, and appropriate implantable cardioverter defibrillator-shock., Results: The cohort comprised 42 patients with Noonan syndrome with multiple lentigines and hypertrophic cardiomyopathy, with a median age at diagnosis of 3.5 (interquartile range, 0.2-12.3) years. Freedom from primary end point was 92.7% (95% CI, 84.7%-100%) 1 year after presentation and 80.9% (95% CI, 70.1%-90.7%) at 5 years. Patients with MLVWT z -score >13.7 showed reduced survival compared with those with <13.7. During a median follow-up of 3.7 years (interquartile range, 2.6-7.9), absolute regression was the most common type of left ventricular remodeling (n=9, 31%), followed by progression (n=6, 21%), and relative regression (n=6, 21%)., Conclusions: These findings provide insights into the natural history of left ventricular hypertrophy, and can help inform clinicians regarding risk stratification and clinical outcomes in patients with Noonan syndrome with multiple lentigines and hypertrophic cardiomyopathy., Competing Interests: Disclosures None.

Noonan syndrome (NS) and related Noonan syndrome with multiple lentigines (NSML) contribute to the pathogenesis of human diseases in the RASopathy family. This family of genetic disorders constitute one of the largest groups of developmental disorders with variable penetrance and severity, associated with distinctive congenital disabilities, including facial features, cardiopathies, growth and skeletal abnormalities, developmental delay/mental retardation, and tumor predisposition. NS was first clinically described decades ago, and several genes have since been identified, providing a molecular foundation to understand their physiopathology and identify targets for therapeutic strategies. These genes encode proteins that participate in, or regulate, RAS/MAPK signalling. The RAS pathway regulates cellular metabolism by controlling mitochondrial homeostasis, dynamics, and energy production; however, little is known about the role of mitochondrial metabolism in NS and NSML. This manuscript comprehensively reviews the most frequently mutated genes responsible for NS and NSML, covering their role in the current knowledge of cellular signalling pathways, and focuses on the pathophysiological outcomes on mitochondria and energy metabolism.

Purpose: Noonan syndrome with multiple lentigines (NSML) is an autosomal dominant disorder presenting with hypertrophic cardiomyopathy (HCM). Up to 85% of NSML cases are caused by mutations in the PTPN11 gene that encodes for the Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 2 (SHP2). We previously showed that low-dose dasatinib protects from the development of cardiac fibrosis in a mouse model of NSML harboring a Ptpn11 Y279C mutation. This study is performed to determine the pharmacokinetic (PK) and pharmacodynamic (PD) properties of a low-dose of dasatinib in NSML mice and to determine its effectiveness in ameliorating the development of HCM., Methods: Dasatinib was administered intraperitoneally into NSML mice with doses ranging from 0.05 to 0.5 mg/kg. PK parameters of dasatinib in NSML mice were determined. PD parameters were obtained for biochemical analyses from heart tissue. Dasatinib-treated NSML mice (0.1 mg/kg) were subjected to echocardiography and assessment of markers of HCM by qRT-PCR. Transcriptome analysis was performed from the heart tissue of low-dose dasatinib-treated mice., Results: Low-dose dasatinib exhibited PK properties that were linear across doses in NSML mice. Dasatinib treatment of between 0.05 and 0.5 mg/kg in NSML mice yielded an exposure-dependent inhibition of c-Src and PZR tyrosyl phosphorylation and inhibited AKT phosphorylation. We found that doses as low as 0.1 mg/kg of dasatinib prevented HCM in NSML mice. Transcriptome analysis identified differentially expressed HCM-associated genes in the heart of NSML mice that were reverted to wild type levels by low-dose dasatinib administration., Conclusion: These data demonstrate that low-dose dasatinib exhibits desirable therapeutic PK properties that is sufficient for effective target engagement to ameliorate HCM progression in NSML mice. These data demonstrate that low-dose dasatinib treatment may be an effective therapy against HCM in NSML patients., (© 2021. The Author(s).)

This study aimed to assess the nature of peripheral nervous system (PNS) involvement in three patients with Noonan syndrome (NS) or NS with multiple lentigines (NSML) as a related RASopathy, presenting primary with intractable neuropathic pain. We studied three unrelated adult patients with severe neuropathic pain and muscle weakness of the limbs. Nerve conduction studies and needle electromyography (EMG) were performed and PNS involvement was assessed by nerve ultrasound imaging, complemented with spinal magnetic resonance imaging (MRI) for the evaluation of proximal nerve segments. Targeted whole-exome sequencing analysis was performed when the diagnosis of NS was suspected. Two patients showed a PTPN11-related dominant and one a LZTR1-related recessive NS or NSML phenotype. The nature of PNS involvement was documented using nerve ultrasound and MRI, showing generalized or multifocal thickening of nerve roots, plexuses and peripheral nerves in all three patients. Nerve imaging using ultrasound and MRI aids in further detailing the nature of neuropathic pain and nerve hypertrophy in patients with NS. This study underlines the relevance of nerve ultrasound in neuropathies and pain syndromes. A NS diagnosis should not be overlooked in longstanding, unexplained neuropathic pain syndromes, with or without muscular weakness. Nerve ultrasound studies can help raise the suspicion for this relatively prevalent inherited multisystem disorder, which is still rather unknown among neurologists, particularly when other potential syndromic features are inconspicuous., (© 2022 Wiley Periodicals LLC.)

LEOPARD syndrome (OMIM #151,100) caused by a germline PTPN11 mutation are characterized as multisystemic anomalies and variable marked phenotypes such as multiple lentigines and cafe´-au-lait spots, electrocardiographic conduction abnormalities, ocular hypertelorism/obstructive cardiomyopathy, pulmonary stenosis, abnormal genitalia, retardation of growth, and deafness. Phenotype overlap complicates clinical discrimination within RASopathies, making the diagnosis of LEOPARD more confusing and challenging. Besides, LEOPARD patients do not usually present with all these typical clinical features, increasing the possibility of underdiagnosis or misdiagnosis.Herein, we report a case of LEOPARD syndrome in a patient who only presented with pigmented skin spots and was initially diagnosed with multiple acquired melanocytic nevi. Subsequent pathological examination confirmed the diagnosis of multiple lentigines rather than melanocytic nevi. A genetic study showed a germline PTPN11 (Tyr279Cys) mutation and raised the suspicion of LEOPARD syndrome. A subsequent ECG examination detected potential cardiac defects and confirmed the diagnosis of LEOPARD. We considered that the potential damage of other systems underlying the skin multiple lentigines should not be ignored. The diagnosis of LEOPARD syndrome in an early stage before cardiac damage has reached a serious and irreversible stage can be meaningful for patients to fully understand the potential risks, complications and prognosis of the disease and to take appropriate precautions to prevent the potential risk of cardiac damage., (© 2021. The Author(s).)

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., (© 2020. International Pediatric Research Foundation, Inc.)

The RASopathies are a family of clinically related disorders caused by mutations affecting genes participating in the RAS-MAPK signaling cascade. Among them, Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML) are allelic conditions principally associated with dominant mutations in PTPN11, which encodes the nonreceptor SH2 domain-containing protein tyrosine phosphatase SHP2. Individual PTPN11 mutations are specific to each syndrome and have opposite consequences on catalysis, but all favor SHP2's interaction with signaling partners. Here, we report on a subject with NS harboring biallelic variants in PTPN11. While the former (p.Leu261Phe) had previously been reported in NS, the latter (p.Thr357Met) is a novel change impairing catalysis. Members of the family carrying p.Thr357Met, however, did not show any obvious feature fitting NSML or within the RASopathy phenotypic spectrum. A major impact of this change on transcript processing and protein stability was excluded. These findings further support the view that NSML cannot be ascribed merely to impaired SHP2's catalytic activity and suggest that PTPN11 mutations causing this condition act through an alternative dominant mechanism., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Multiple lentigines syndrome is an autosomal dominant inherited condition with variable expressivity that is also known as LEOPARD syndrome. LEOPARD stands for lentigines, electrocardiographic conduction defects, ocular hypertelorism, pulmonary valve stenosis, abnormalities of genitalia, retardation of growth, and deafness. LEOPARD syndrome most frequently develops secondary to a missense mutation of protein-tyrosine phosphatase nonreceptor type 11 gene, which encodes tyrosine phosphatase. The missense mutation p.Tyr279Cys can either occur as a de novo mutation or affect multiple family members. Although hypertrophic cardiomyopathy is not part of the LEOPARD acronym, it is the most frequent cardiac anomaly observed in this syndrome. The recognition of increased left or right ventricular wall thickness in patients with LEOPARD syndrome may have significant impact on their clinical course similar to classic hypertrophic cardiomyopathy, which may require septal reduction procedures for relief of left or right ventricular outflow tract obstruction or implantable cardioverter-defibrillator placement for sudden cardiac death prevention. We describe a case series of a family with diffuse lentigines and hypertrophic cardiomyopathy in which the son carries the protein-tyrosine phosphatase nonreceptor type 11 (p.Tyr279Cys) gene mutation and both the son and daughter underwent left ventricular myectomy at an early age. In conclusion, our case series of a family with LEOPARD syndrome illustrates the importance of recognizing hypertrophic cardiomyopathy as part of this syndrome., (Copyright © 2020 Elsevier Inc. All rights reserved.)

SHP2 is a non-receptor protein tyrosine phosphatase encoded by the PTPN11 gene in human. Clinically, SHP2 has been identified as a causal factor of several diseases, such as Noonan syndrome, LEOPARD syndrome as well as myeloid malignancies. Interestingly, both loss-of-function and gain-of-function mutations occur in the PTPN11 gene. Analyses by biochemical and cell biological means as well as probing with small molecule compounds have demonstrated that SHP2 has both phosphatase-dependent and independent functions. In comparison with its phosphatase activity, the non-phosphatase-like function of SHP2 has not been well introduced or summarized. This review mainly focuses on the phosphatase-independent functions and its regulation by small molecule compounds as well as their use for disease therapy., Competing Interests: Declaration of competing interest There is no conflict of interest., (Copyright © 2020 The Authors. Production and hosting by Elsevier B.V. All rights reserved.)

Noonan syndrome with multiple lentigines (NSML) is a rare autosomal dominant disorder that presents with cardio-cutaneous-craniofacial defects. Hypertrophic cardiomyopathy (HCM) represents the major life-threatening presentation in NSML. Mutations in the PTPN11 gene that encodes for the protein tyrosine phosphatase (PTP), SHP2, represents the predominant cause of HCM in NSML. NSML-associated PTPN11 mutations render SHP2 catalytically inactive with an "open" conformation. NSML-associated PTPN11 mutations cause hypertyrosyl phosphorylation of the transmembrane glycoprotein, protein zero-related (PZR), resulting in increased SHP2 binding. Here we show that NSML mice harboring a tyrosyl phosphorylation-defective mutant of PZR (NSML/PZRY242F) that is defective for SHP2 binding fail to develop HCM. Enhanced AKT/S6 kinase signaling in heart lysates of NSML mice was reversed in NSML/PZRY242F mice, demonstrating that PZR/SHP2 interactions promote aberrant AKT/S6 kinase activity in NSML. Enhanced PZR tyrosyl phosphorylation in the hearts of NSML mice was found to drive myocardial fibrosis by engaging an Src/NF-κB pathway, resulting in increased activation of IL-6. Increased expression of IL-6 in the hearts of NSML mice was reversed in NSML/PZRY242F mice, and PZRY242F mutant fibroblasts were defective for IL-6 secretion and STAT3-mediated fibrogenesis. These results demonstrate that NSML-associated PTPN11 mutations that induce PZR hypertyrosyl phosphorylation trigger pathophysiological signaling that promotes HCM and cardiac fibrosis.

Src homology 2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2), encoded by PTPN11, regulates cell proliferation, differentiation, apoptosis and survival via releasing intramolecular autoinhibition and modulating various signaling pathways, such as mitogen-activated protein kinase (MAPK) pathway. Mutations and aberrant expression of SHP2 are implicated in human developmental disorders, leukemias and several solid tumors. As an oncoprotein in some cancers, SHP2 represents a rational target for inhibitors to interfere. Nevertheless, its tumor suppressive effect has also been uncovered, indicating the context-specificity. Even so, two types of SHP2 inhibitors including targeting catalytic pocket and allosteric sites have been developed associated with resolved cocrystal complexes. Herein, we describe its structure, biological function, deregulation in human diseases and summarize recent advance in development of SHP2 inhibitors, trying to give an insight into the therapeutic potential in future., Competing Interests: Declaration of competing interest We declare no other conflicts of interest., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

RASopathies are developmental diseases caused by mutations in rat sarcoma-mitogen-activated protein kinase pathway genes. These disorders, such as Noonan syndrome (NS) and NS-related disorders (NSRD), including cardio-facio-cutaneous (CFC) syndrome, Costello syndrome (CS), and NS with multiple lentigines (NSML; also known as LEOPARD syndrome), have a similar systemic phenotype. A wide spectrum of congenital heart disease and hypertrophic cardiomyopathy (HCMP) can exhibit major associated characteristics. A retrospective study was conducted at the Mackay Memorial Hospital, National Taiwan University Hospital, Buddhist Tzu-Chi General Hospital, Chang-Gung Memorial Hospital, Taichung Veterans General Hospital, and Chung Shan Medical University Hospital from January 2007 to December 2018. We reviewed the clinical records of 76 patients with a confirmed molecular diagnosis of RASopathies, including NS, CS, CFC syndrome, and NSML. We evaluated the demographic data and medical records with clinical phenotypes of cardiac structural anomalies using cross-sectional and color Doppler echocardiography, electrocardiographic findings, and follow-up data. A total of 47 (61.8%) patients had cardiac abnormalities. The prevalence of cardiac lesions according to each syndrome was 62.7, 50.0, 60.0, and 66.7% in patients with NS, CFC syndrome, CS, and NSML, respectively. An atrial septal defect was usually combined with other cardiac abnormalities, such as pulmonary stenosis (PS), HCMP, ventricular septal defect, or patent ductus arteriosus. Patients with NS most commonly showed PS. In patients with NSRD and cardiac abnormalities, HCMP (29.4%) was the most commonly observed cardiac lesion. PTPN11 was also the most frequently detected mutation in patients with NS and NSRD. Cardiac abnormalities were the most common symptoms observed in patients with RASopathies at the time of their first hospital visit. Performing precise analyses of genotype-cardiac phenotype correlations in a larger cohort will help us accurately diagnose RASopathy as soon as possible., (© 2019 Wiley Periodicals, Inc.)

Objectives: To give an overview of the genetic and structural abnormalities occurring in fetuses with nuchal translucency (NT) measurement exceeding the 95th percentile at first-trimester screening and to investigate which of these abnormalities would be missed if cell-free fetal DNA (cfDNA) were used as a first-tier screening test for chromosomal abnormalities., Methods: This is a national study including 1901 pregnancies with NT≥95th percentile referred to seven university hospitals in the Netherlands between 1 January 2010 and 1 January 2016. All cases with unknown pregnancy outcome were excluded. Results of detailed ultrasound examinations, karyotyping, genotyping, pregnancy and neonatal outcomes, investigation by a clinical geneticist and post-mortem investigations were collected., Results: In total, 821 (43%) pregnancies had at least one abnormality. The rate of abnormalities was 21% for fetuses with NT between 95 th and 99 th percentile and 62% for fetuses with NT≥99 th percentile. Prevalence of single-gene disorders, submicroscopic, chromosomal and structural abnormalities was 2%, 2%, 30% and 9%, respectively., Conclusion: Although cfDNA is superior to the combined test, especially for the detection of trisomy 21, 34% of the congenital abnormalities occurring in fetuses with increased NT may remain undetected in the first trimester of pregnancy, unless cfDNA is used in combination with fetal sonographic assessment, including NT measurement., (© 2019 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.)

We report the case of a 14 years and 8 months girl, who is the first child of nonconsanguineous parents, with short stature, obstructive hypertrophic cardiomyopathy, multiple facial lentigines, high and wide forehead, downslanting palpebral fissures, low-set ears, short neck, and pectus excavatum; all features suggestive of Noonan syndrome with multiple lentigines (NSML). In addition, the patient exhibited craniosynostosis. Molecular analysis of rats sarcoma (RAS)/mitogen-activated protein kinase (MAPK) pathway genes with high-resolution melting curve analysis followed by sequencing showed a RAF1 amino acid substitution of valine to glycine at position 263 (p.V263G). The present report provides clinical data regarding the first association of a RAF1 variant and craniosynostosis in a patient with clinical diagnosis of NSML., (© 2019 Wiley Periodicals, Inc.)

RASopathies are a group of genetic disorders due to dysregulation of the RAS-MAPK signaling pathway, which is important in regulating cell growth, proliferation, and differentiation. These include Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NSML), cardiofaciocutaneous (CFC) syndrome, and Costello syndrome (CS), clinical manifestations include growth retardation, developmental delay, cardiac defects, and specific dysmorphic features. There were abundant publications describing the genotype and phenotype from the Western populations. However, detailed study of RASopathies in Chinese population is lacking. We present here the largest cohort of RASopathies ever reported in Chinese populations, detailing the mutation spectrum and clinical phenotypes of these patients. The Clinical Genetic Service, Department of Health, and Queen Mary Hospital are tertiary referral centers for genetic disorders in Hong Kong. We retrospectively reviewed all the genetically confirmed cases of RASopathies, including NS, NSML, CFC syndrome, and CS, over the past 29 years (from 1989 to 2017). Analyses of the mutation spectrum and clinical phenotypes were performed. One hundred and ninety-one ethnic Chinese patients with genetically confirmed RASopathies were identified, including 148 patients with NS, 23 NSML, 12 CFC syndrome, and eight CS. We found a lower incidence of hypertrophic cardiomyopathy in individuals with NSML (27.3%), and NS caused by RAF1 mutations (62.5%). Another significant finding was for those NS patients with myeloproliferative disorder, the mutations fall within Exon 3 of PTPN11 but not only restricted to the well-known hotspots, that is, p.Asp61 and p.Thr731, which suggested that re-evaluation of the current tumor surveillance recommendation maybe warranted., (© 2019 Wiley Periodicals, Inc.)

Noonan syndrome with multiple lentigines (NSML), formerly known as LEOPARD Syndrome, is a rare autosomal dominant disorder. Approximately 90% of NSML cases are caused by missense mutations in the PTPN11 gene which encodes the protein tyrosine phosphatase SHP2. A human induced pluripotent stem cell (iPSC) line was generated using peripheral blood mononuclear cells (PBMCs) from a patient with NSML that carries a gene mutation of p.Q510P on the PTPN11 gene using non-integrating Sendai virus technique. This iPSC line offers a useful resource to study the disease pathophysiology and a cell-based model for drug development to treat NSML., (Published by Elsevier B.V.)

Multifocal atrial tachycardia (MAT) has a well-known association with Costello syndrome, but is rarely described with related RAS/MAPK pathway disorders (RASopathies). We report 11 patients with RASopathies (Costello, Noonan, and Noonan syndrome with multiple lentigines [formerly LEOPARD syndrome]) and nonreentrant atrial tachycardias (MAT and ectopic atrial tachycardia) demonstrating overlap in cardiac arrhythmia phenotype. Similar overlap is seen in RASopathies with respect to skeletal, musculoskeletal and cutaneous abnormalities, dysmorphic facial features, and neurodevelopmental deficits. Nonreentrant atrial tachycardias may cause cardiac compromise if sinus rhythm is not restored expeditiously. Typical first-line supraventricular tachycardia anti-arrhythmics (propranolol and digoxin) were generally not effective in restoring or maintaining sinus rhythm in this cohort, while flecainide or amiodarone alone or in concert with propranolol were effective anti-arrhythmic agents for acute and chronic use. Atrial tachycardia resolved in all patients. However, a 4-month-old boy from the cohort was found asystolic (with concurrent cellulitis) and a second patient underwent cardiac transplant for heart failure complicated by recalcitrant atrial arrhythmia. While propranolol alone frequently failed to convert or maintain sinus rhythm, fleccainide or amiodarone, occasionally in combination with propranolol, was effective for RASopathy patient treatment for nonreentrant atrial arrhythmia. Our analysis shows that RASopathy patients may have nonreentrant atrial tachycardia with and without associated cardiac hypertrophy. While nonreentrant arrhythmia has been traditionally associated with Costello syndrome, this work provides an expanded view of RASopathy cardiac arrhythmia phenotype as we demonstrate mutant proteins throughout this signaling pathway can also give rise to ectopic and/or MAT., (© 2018 Wiley Periodicals, Inc.)

Catalytically activating mutations in Ptpn11 , which encodes the protein tyrosine phosphatase SHP2, cause 50% of Noonan syndrome (NS) cases, whereas inactivating mutations in Ptpn11 are responsible for nearly all cases of the similar, but distinct, developmental disorder Noonan syndrome with multiple lentigines (NSML; formerly called LEOPARD syndrome). However, both types of disease mutations are gain-of-function mutations because they cause SHP2 to constitutively adopt an open conformation. We found that the catalytic activity of SHP2 was required for the pathogenic effects of gain-of-function, disease-associated mutations on the development of hydrocephalus in the mouse. Targeted pan-neuronal knockin of a Ptpn11 allele encoding the active SHP2 E76K mutant resulted in hydrocephalus due to aberrant development of ependymal cells and their cilia. These pathogenic effects of the E76K mutation were suppressed by the additional mutation C459S, which abolished the catalytic activity of SHP2. Moreover, ependymal cells in NSML mice bearing the inactive SHP2 mutant Y279C were also unaffected. Mechanistically, the SHP2 E76K mutant induced developmental defects in ependymal cells by enhancing dephosphorylation and inhibition of the transcription activator STAT3. Whereas STAT3 activity was reduced in Ptpn11 E76K/+ cells, the activities of the kinases ERK and AKT were enhanced, and neural cell-specific Stat3 knockout mice also manifested developmental defects in ependymal cells and cilia. These genetic and biochemical data demonstrate a catalytic-dependent role of SHP2 gain-of-function disease mutants in the pathogenesis of hydrocephalus., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Noonan Syndrome with Multiple Lentigines (NSML) is associated with congenital heart disease in form of pulmonary valve stenosis and hypertrophic cardiomyopathy (HCM). Genetically, NSML is primarily caused by mutations in the non-receptor protein tyrosine phosphatase SHP2. Importantly, certain SHP2 mutations such as Q510E can cause a particularly severe form of HCM with heart failure in infancy. Due to lack of insight into the underlying pathomechanisms, an effective custom-tailored therapy to prevent heart failure in these patients has not yet been found. SHP2 regulates numerous signaling cascades governing cell growth, differentiation, and survival. Experimental models have shown that NSML mutations in SHP2 cause dysregulation of downstream signaling, in particular involving the protein kinase AKT. AKT, and especially the isoform AKT1, has been shown to be a major regulator of cardiac hypertrophy. We therefore hypothesized that hyperactivation of AKT1 is required for the development of Q510E-SHP2-induced HCM. We previously generated a transgenic mouse model of NSML-associated HCM induced by Q510E-SHP2 expression in cardiomyocytes starting before birth. Mice display neonatal-onset HCM with initially preserved contractile function followed by functional decline around 2months of age. As a proof-of-principle study, our current goal was to establish to which extent a genetic reduction in AKT1 rescues the Q510E-SHP2-induced cardiac phenotype in vivo. AKT1 deletion mice were crossed with Q510E-SHP2 transgenic mice and the resulting compound mutant offspring analyzed. Homozygous deletion of AKT1 greatly reduced viability in our NSML mouse model, whereas heterozygous deletion of AKT1 in combination with Q510E-SHP2 expression was well tolerated. Despite normalization of pro-hypertrophic signaling downstream of AKT, heterozygous deletion of AKT1 did not ameliorate cardiac hypertrophy induced by Q510E-SHP2. However, the functional decline caused by Q510E-SHP2 expression was effectively prevented by reducing AKT1 protein. This demonstrates that AKT1 plays an important role in the underlying pathomechanism. Furthermore, the functional rescue was associated with an increase in the capillary-to-cardiomyocyte ratio and normalization of capillary density per tissue area in the compound mutant offspring. We therefore speculate that limited oxygen supply to the hypertrophied cardiomyocytes may contribute to the functional decline observed in our mouse model of NSML-associated HCM., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML) are autosomal dominant developmental disorders. NS and NSML are caused by abnormalities in genes that encode proteins related to the RAS-MAPK pathway, including PTPN11, RAF1, BRAF, and MAP2K. In this study, we diagnosed ten NS or NSML patients via targeted sequencing or whole exome sequencing (TS/WES)., Methods: TS/WES was performed to identify mutations in ten Chinese patients who exhibited the following manifestations: potential facial dysmorphisms, short stature, congenital heart defects, and developmental delay. Sanger sequencing was used to confirm the suspected pathological variants in the patients and their family members., Results: TS/WES revealed three mutations in the PTPN11 gene, three mutations in RAF1 gene, and four mutations in BRAF gene in the NS and NSML patients who were previously diagnosed based on the abovementioned clinical features. All the identified mutations were determined to be de novo mutations. However, two patients who carried the same mutation in the RAF1 gene presented different clinical features. One patient with multiple lentigines was diagnosed with NSML, while the other patient without lentigines was diagnosed with NS. In addition, a patient who carried a hotspot mutation in the BRAF gene was diagnosed with NS instead of cardiofaciocutaneous syndrome (CFCS)., Conclusions: TS/WES has emerged as a useful tool for definitive diagnosis and accurate genetic counseling of atypical cases. In this study, we analyzed ten Chinese patients diagnosed with NS and related disorders and identified their correspondingPTPN11, RAF1, and BRAF mutations. Among the target genes, BRAF showed the same degree of correlation with NS incidence as that of PTPN11 or RAF1.

Noonan Syndrome with Multiple Lentigines (NSML, formerly LEOPARD syndrome) is an autosomal dominant "RASopathy" disorder manifesting in congenital heart disease. Most cases of NSML are caused by catalytically inactivating mutations in the protein tyrosine phosphatase (PTP), non-receptor type 11 (PTPN11), encoding the SH2 domain-containing PTP-2 (SHP2) protein. We previously generated knock-in mice harboring the PTPN11 mutation Y279C, one of the most common NSML alleles; these now-termed SHP2Y279C/+ mice recapitulate the human disorder and develop hypertrophic cardiomyopathy (HCM) by 12 weeks of age. Functionally, heart and/or cardiomyocyte lysates from SHP2Y279C/+ mice exhibit increased basal and agonist-induced AKT and mTOR activities. Here, we sought to determine whether we could reverse the hypertrophy in SHP2Y279C/+ mice using ARQ 092, an oral and selective allosteric AKT inhibitor currently in clinical trials for patients with PI3K/AKT-driven tumors or Proteus syndrome. We obtained echocardiographs of SHP2Y279C/+ and wildtype (SHP2+/+) littermates, either in the presence or absence of ARQ 092 at 12, 14, and 16 weeks of age. While SHP2Y279C/+ mice developed significant left ventricular hypertrophy by 12 weeks, as indicated by decreased chamber dimension and increased posterior wall thickness, treatment of SHP2Y279C/+ mice with ARQ 092 normalized the hypertrophy in as early as 2 weeks following treatment, with hearts comparable in size to those in wildtype (SHP2+/+) mice. In addition, we observed an increase in fractional shortening (FS%) in SHP2Y279C/+ mice, an effect of increased compensatory hypertrophy, which was not apparent in SHP2Y279C/+ mice treated with ARQ 092, suggesting functional improvement of HCM upon treatment with the AKT inhibitor. Finally, we found that ARQ 092 specifically inhibited AKT activity, as well as its downstream effectors, PRAS and S6RP in NSML mice. Taken together, these data suggest ARQ 092 may be a promising novel therapy for treatment of hypertrophy in NSML patients.

Existing literature only reports a few patients with Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML) who underwent cochlear implantation (CI). The present study describes four NS patients and one NSML patient with a PTPN11 mutation. They all had severe to profound hearing loss, and they received a CI. The age at which the CI surgery occurred ranged from 1 to 13 years old, and the audiological results in all five patients improved after the CI. Otological and audiological examinations in NS and NSML are important, and for those with severe hearing loss, the CI surgery improved the audiological outcome regardless of age., (Published by Elsevier B.V.)

Introduction: RASopathies include disorders generally characterized by developmental delay, specific heart defects, short stature, cardiac hypertrophy, and facial dysmorphisms. Next-generation sequencing (NGS)-based panels have widespread acceptance as a diagnostic tool for RASopathies., Materials and Methods: The first 126 patients evaluated by clinical examination and the NGS RASopathy panel at the Children's Hospital of Philadelphia were enrolled. We calculated diagnosis rate, correlated reported clinical findings with positive or negative test results, and identified final molecular diagnoses in 28/96 patients who tested negative for RASopathies., Results: Twenty-four patients had pathogenic variants on the RASopathy panel, for a diagnostic yield of 19%. Reported features of pulmonic stenosis and ptosis were significantly correlated with a positive test result; no reported features were significantly correlated with a negative test result. We identified 27 different alternative diagnoses for patients originally suspected of having RASopathies., Discussion: This study provides information that can assist in guiding differential diagnosis and genetic testing for patients suspected of having a RASopathy disorder.Genet Med advance online publication 20 October 2016.

Dilated cardiomyopathy (DCM) is a life-threatening disorder whose genetic basis is heterogeneous and mostly unknown. Five Arab Christian infants, aged 4-30 months from four families, were diagnosed with DCM associated with mild skin, teeth, and hair abnormalities. All passed away before age 3. A homozygous sequence variation creating a premature stop codon at  PPP1R13L encoding the iASPP protein was identified in three infants and in the mother of the other two. Patients' fibroblasts and PPP1R13L -knocked down human fibroblasts presented higher expression levels of pro-inflammatory cytokine genes in response to lipopolysaccharide, as well as Ppp1r13l -knocked down murine cardiomyocytes and hearts of Ppp1r13l -deficient mice. The hypersensitivity to lipopolysaccharide was NF-κB-dependent, and its inducible binding activity to promoters of pro-inflammatory cytokine genes was elevated in patients' fibroblasts. RNA sequencing of Ppp1r13l -knocked down murine cardiomyocytes and of hearts derived from different stages of DCM development in Ppp1r13l -deficient mice revealed the crucial role of iASPP in dampening cardiac inflammatory response. Our results determined  PPP1R13L as the gene underlying a novel autosomal-recessive cardio-cutaneous syndrome in humans and strongly suggest that the fatal DCM during infancy is a consequence of failure to regulate transcriptional pathways necessary for tuning cardiac threshold response to common inflammatory stressors., (© 2017 The Authors. Published under the terms of the CC BY 4.0 license.)

Multiple café-au-lait macules (CALM) are usually associated with neurofibromatosis type 1 (NF1), one of the most common hereditary disorders. However, a group of genetic disorders presenting with CALM have mutations that are involved in human skin pigmentation regulation signaling pathways, including KIT ligand/KIT proto‑oncogene receptor tyrosine kinase and Ras/mitogen‑activated protein kinase. These disorders, which include Legius syndrome, Noonan syndrome with multiple lentigines or LEOPARD syndrome, and familial progressive hyperpigmentation) are difficult to distinguish from NF1 at early stages, using skin appearance alone. Furthermore, certain syndromes are clinically overlapping and molecular testing is a vital diagnostic method. The present review aims to provide an overview of these 'NF1‑like' inherited diseases and recommend a cost‑effective strategy for making a clear diagnosis among these diseases with an ambiguous borderline.

LEOPARD syndrome (LS) is an autosomal dominant inherited disorder primarily caused by mutations in the PTPN11, RAF1 and BRAF genes. Characteristic features include lentigines, craniofacial dysmorphism, myocardium or valve abnormalities, eletrocardiographic conduction defects and deafness. LS, neurofibromatosis type 1, Noonan syndrome and Legius syndrome are a group of highly overlapped disorders termed 'RASopathies'. Therefore, clinical discrimination between these syndromes represents a huge challenge. The present study reports a young child diagnosed with LS via identification of a common p.Thr468Met mutation in PTPN11. Taking into account two Taiwanese LS cases with an identical mutation, Thr468Met is likely to be the most prevalent mutation in the Chinese population. Furthermore, this study suggests that a clinical diagnosis of LS should be considered for individuals with congenital cardiac defects and atypical lentigines (i.e., light brown freckles) scattered particularly on the face.

Background: Noonan syndrome with multiple lentigines (NSML), formerly known as LEOPARD syndrome, is an autosomal-dominant disorder characterised by lentigines, EKG abnormalities, ocular hypertelorism, pulmonic stenosis, abnormal genitalia, growth retardation and deafness. There is significant clinical overlap between NSML and other disorders that result from dysregulated rat sarcoma/mitogen-activated protein kinase pathway (RASopathies). Except for neurofibromatosis type 1, other RASopathies are not known to be typically associated with neurogenic tumours., Methods and Results: We evaluated patients from three families with pigmentary skin lesions, progressive neuropathy, enlarged nerves, massive burden of paraspinal tumours (neurofibroma was confirmed in one patient) and a clinical diagnosis of NSML. All patients had a mutation in the protein tyrosine phosphatase catalytic domain of the PTPN11 gene; two unrelated patients had the p.Thr468Met mutation, while the family consisting of two affected individuals harboured the p.Thr279Cys mutation. Molecular analysis performed on hypertrophic nerve tissue did not disclose a second somatic hit in NF1, PTPN11, NF2 or SMARCB1 genes., Conclusions: Neurogenic tumours and hypertrophic neuropathy are unusual complications of NSML and may be an under-recognised manifestation that would warrant surveillance. Our observation may also have implications for other disorders caused by RAS-pathway dysregulation., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

SHP2, encoded by the PTPN11 gene, is a protein tyrosine phosphatase that plays a key role in the proliferation of cells via RAS-ERK activation. SHP2 also promotes Wnt signaling by dephosphorylating parafibromin. Germline missense mutations of PTPN11 are found in more than half of patients with Noonan syndrome (NS) and LEOPARD syndrome (LS), both of which are congenital developmental disorders with multiple common symptoms. However, whereas NS-associated PTPN11 mutations give rise to gain-of-function SHP2 mutants, LS-associated SHP2 mutants are reportedly loss-of-function mutants. To determine the phosphatase activity of LS-associated SHP2 more appropriately, we performed an in vitro phosphatase assay using tyrosine-phosphorylated parafibromin, a biologically relevant substrate of SHP2 and the positive regulator of Wnt signaling that is activated through SHP2-mediated dephosphorylation. We found that LS-associated SHP2 mutants (Y279C, T468M, Q506P, and Q510E) exhibited a substantially reduced phosphatase activity toward parafibromin when compared with wild-type SHP2. Furthermore, each of the LS-associated mutants displayed a differential degree of decrease in phosphatase activity. Deviation of the SHP2 catalytic activity from a certain range, either too strong or too weak, may therefore lead to similar clinical outcomes in NS and LS, possibly through an imbalanced Wnt signal caused by inadequate dephosphorylation of parafibromin., (Copyright © 2015 Elsevier Inc. All rights reserved.)

LEOPARD syndrome (LS, OMIM 151100) is a rare monogenic disorder. The name is an acronym of its major features such as multiple lentigines, electrocardiographic conduction defects, ocular hypertelorism, pulmonary stenosis, abnormalities of genitalia, retardation of growth and sensorineural deafness. LS develops due to mutations in the protein-tyrosine phosphatase nonreceptor-type 11, PTPN11. Here, we have investigated a 51-year-old Hungarian male patient affected by LS. Direct sequencing of the PTPN11 gene revealed a worldwide recurrent missense mutation (c.836A/G; p.Tyr279Cys), which has been previously identified in 47 LS patients. Comparison of the clinical phenotypes of our patient and the ones reported in the literature demonstrates great phenotypic diversity despite the same genotype.

Noonan syndrome (NS) and related disorders, such as NS with multiple lentigines (formerly called LEOPARD syndrome), cardiofaciocutaneous syndrome, and Costello syndrome, constitute an important group of developmental malformation syndromes with variable clinical and molecular features. Their underlying pathophysiologic mechanism involves dysregulation of the Ras/mitogen-activated protein kinase signaling pathway, an essential mediator of developmental and growth processes in the prenatal and postnatal setting. Malignant tumor development is an important complication encountered in other RASopathies, such as neurofibromatosis type 1, but the neoplastic risks and incidence of malignant tumors are less clearly defined in NS and related disorders of the Noonan spectrum. Malignant tumor development remains an important complication variably seen in the RASopathies and, thus, a clear understanding of the underlying risks is essential for appropriate clinical care in this patient population. This review discusses previously published reports of malignancies in individuals with RASopathies of the Noonan spectrum., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

LEOPARD syndrome (LS) is an autosomal dominant condition with multiple anomalies, including multiple lentigines. LS is caused by mutations in PTPN11, encoding the protein tyrosine phosphatase, SHP-2. We report here 2 unrelated Japanese cases of LS with different PTPN11 mutations (p.Y279C and p.T468P). To elucidate the pathogenesis of multiple lentigines in LS, ultrastructural and immunohistochemical analyses of lentigines and non-lesional skin were performed. Numerous mature giant melanosomes in melanocytes and keratinocytes were observed in lentigines. In addition, the levels of expression of endothelin-1 (ET-1), phosphorylated Akt, mTOR and STAT3 in the epidermis in lentigines were significantly elevated compared with non-lesional skin. In in vitro assays, melanin synthesis in human melanoma cells expressing SHP-2 with LS-associated mutations was higher than in cells expressing normal SHP-2, suggesting that LS-associated SHP-2 mutations might enhance melanin synthesis in melanocytes, and that the activation of Akt/mTOR signalling may contribute to this process.

Noonan syndrome with multiple lentigines (NSML) is primarily caused by mutations in the nonreceptor protein tyrosine phosphatase SHP2 and associated with congenital heart disease in the form of pulmonary valve stenosis and hypertrophic cardiomyopathy (HCM). Our goal was to elucidate the cellular mechanisms underlying the development of HCM caused by the Q510E mutation in SHP2. NSML patients carrying this mutation suffer from a particularly severe form of HCM. Drawing parallels to other, more common forms of HCM, we hypothesized that altered Ca(2+) homeostasis and/or sarcomeric mechanical properties play key roles in the pathomechanism. We used transgenic mice with cardiomyocyte-specific expression of Q510E-SHP2 starting before birth. Mice develop neonatal onset HCM with increased ejection fraction and fractional shortening at 4-6 wk of age. To assess Ca(2+) handling, isolated cardiomyocytes were loaded with fluo-4. Q510E-SHP2 expression increased Ca(2+) transient amplitudes during excitation-contraction coupling and increased sarcoplasmic reticulum Ca(2+) content concurrent with increased expression of sarco(endo)plasmic reticulum Ca(2+)-ATPase. In skinned cardiomyocyte preparations from Q510E-SHP2 mice, force-velocity relationships and power-load curves were shifted upward. The peak power-generating capacity was increased approximately twofold. Transmission electron microscopy revealed that the relative intracellular area occupied by sarcomeres was increased in Q510E-SHP2 cardiomyocytes. Triton X-100-based myofiber purification showed that Q510E-SHP2 increased the amount of sarcomeric proteins assembled into myofibers. In summary, Q510E-SHP2 expression leads to enhanced contractile performance early in disease progression by augmenting intracellular Ca(2+) cycling and increasing the number of power-generating sarcomeres. This gives important new insights into the cellular pathomechanisms of Q510E-SHP2-associated HCM., (Copyright © 2015 the American Physiological Society.)

LEOPARD syndrome is an autosomal dominant disease caused by germline mutations in the RAS-MAPK (mitogen-activated protein kinase) pathway. LEOPARD is an acronym for the main manifestations of the syndrome, namely, multiple Lentigines, Electrocardiographic conduction abnormalities, Ocular hypertelorism, Pulmonary stenosis, Abnormalities of genitalia, Retardation of growth, and sensorineural Deafness. None of these characteristic features, however, are pathognomonic of LEOPARD syndrome, and since they are highly variable, they are often not present at the time of diagnosis. We describe 2 cases of LEOPARD syndrome without hearing loss or pulmonary stenosis in which diagnosis was confirmed by identification of a mutation in the PTPN11 gene. Regular monitoring is important for the early detection of complications, as these can occur at any time during the course of disease., (Copyright © 2014 Elsevier España, S.L.U. y AEDV. All rights reserved.)

Introduction: Noonan syndrome (NS) and other syndromes with a similar phenotype, such as LEOPARD, cardiofaciocutaneous, Costello and Legius, are associated to mutations in genes included in the RAS/MAPK pathway (RASopathies), which is an important signalling pathway related to cell proliferation. Tonsillar descent into the upper cervical spinal canal, known as Arnold-Chiari malformation (ACM), has been reported in patients with NS and this has led some researchers to suggest that ACM could be part of the phenotypic spectrum of NS. We report two cases of NS and ACM., Case Reports: Case 1: 29-year-old female with Noonan phenotype who underwent surgery at the age of nine years due to pulmonary valve stenosis. At the age of 27, she presented symptomatic ACM that required surgical decompression. She presented the c.922A>G (N308D) mutation in the gene PTPN that belongs to the RAS/MAPK pathway. Case 2: a 10-year-old female with Noonan phenotype and asymptomatic ACM detected in magnetic resonance imaging of the brain. She was a carrier of the c.923A>G (N308S) mutation in gene PTPN11., Conclusions: Six patients with this association have been found in the literature, four with the Noonan phenotype and two with LEOPARD. Our two patients provide supplementary evidence that backs up the hypothesis by which ACM would be part of the phenotypic spectrum of NS. The small number of reported cases of patients with this association does not allow us to draw up recommendations about when and how often neuroimaging studies should be performed; a careful neurological examination, however, should be included in the anticipatory health guidelines in syndromes involving the RAS/MAPK pathway.

Background: LEOPARD syndrome (LS) belongs to the family of neuro-cardio-facio-cutaneous syndromes, which include Neurofibromatosis-1 (NF1), Noonan syndrome, Costello Syndrome, cardio-facio-cutaneous syndrome, Noonan-like syndrome with loose anagen hair and Legius syndrome. These conditions are caused by mutations in genes encoding proteins involved in the RAS-MAPK cellular pathway. Clinical heterogeneity and phenotype overlaps across those different syndromes is already recognized., Case Presentation: We hereby report a heterozygous de novo mutation in the PTPN11 gene (c.1403C > T) manifesting with a clinical picture of LS during childhood, and later development of neuropathic pain with hypertrophic plexi, which are typically observed in NF1 but have not been reported in LS., Conclusion: LS caused by PTPN11 mutations may be associated with hypertrophic roots and plexi. Consequently, clinicians should be aware of the possible development of neuropathic pain and consider specific diagnostic work-up and management.

Noonan syndrome with multiple lentigines (NSML), formerly referred to as LEOPARD syndrome, is a rare autosomal-dominant condition, characterized by multiple lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, growth retardation, and sensorineural deafness. To date, PTPN11, RAF1, and BRAF have been reported to be causal for NSML. We report on a 13-year-old Japanese boy, who was diagnosed with NSML. He was found to have a novel heterozygous missense variant (c.305A > G; p.E102G) in MAP2K1, a gene mostly causal for cardio-facio-cutaneous syndrome (CFCS). He manifested fetal macrosomia, and showed hypotonia and poor sucking in the neonatal period. He had mild developmental delay, and multiple lentigines appearing at approximately age 3 years, as well as flexion deformity of knees bilaterally, subtle facial characteristics including ocular hypertelorism, sensorineural hearing loss, and precocious puberty. He lacked congenital heart defects or hypertrophic cardiomyopathy, frequently observed in patients with NSML, mostly caused by PTPN11 mutations. He also lacked congenital heart defects, characteristic facial features, or intellectual disability, frequently observed in those with CFCS caused by MAP2K1 or MAP2K2 mutations. This may be the first patient clinically diagnosed with NSML, caused by a mutation in MAP2K1., (© 2014 Wiley Periodicals, Inc.)