Atypical left-ventricular hypertrophy with apical aneurysm in leopard syndrome.

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.

Natural History of Hypertrophic Cardiomyopathy in Noonan Syndrome With Multiple Lentigines.

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.

Effects of Noonan Syndrome-Germline Mutations on Mitochondria and Energy Metabolism.

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.

Neurological features of Noonan syndrome and related RASopathies: Pain and nerve enlargement characterized by nerve ultrasound.

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.

Low-dose Dasatinib Ameliorates Hypertrophic Cardiomyopathy in Noonan Syndrome with Multiple Lentigines.

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 Ptpn11Y279C 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.

Leopard syndrome: the potential cardiac defect underlying skin phenotypes.

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.

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

BACKGROUND: Noonan Syndrome with Multiple Lentigines (NSML) and Noonan Syndrome (NS) can be difficult to differentiate clinically in early childhood. This study aims to describe characteristics of the ventricular septum that may differentiate NSML from NS. We hypothesize that the shape of the ventricular septum determined by echocardiography correlates with genotype and may distinguish patients with NSML from those with NS. METHODS: We analyzed data from 17 NSML and 67 NS patients. Forty normal and 30 sarcomeric hypertrophic cardiomyopathy (HCM) patients were included as controls. Septal morphology was qualitatively evaluated, and septal angle was measured quantitatively at end diastole. We recorded the presence of a ventricular septal bulge (VSB) and reviewed genetic testing results for each patient. RESULTS: The most important findings were a sigmoid septum (71%) and VSB (71%) in NSML. NSML septal angle was decreased compared to the normal and sarcomeric HCM control groups, respectively (149 ± 13 vs. 177 ± 3, p < 0.001; 149 ± 13 vs. 172 ± 7, p < 0.001). NS septal angle was similar to the controls (176 ± 6 vs. 177 ± 3, p > 0.5; 176 ± 6 vs. 172 ± 7, p > 0.5). NSML-linked pathogenic variants were associated with sigmoid septum and VSB. CONCLUSIONS: These findings provide novel phenotypic evidence to clinicians that may offer incremental diagnostic value in counseling families in ambiguous NSML/NS cases. IMPACT: Characteristics of the ventricular septum are linked to specific gene variants that cause NSML and NS. Sigmoid septum and VSB are associated with NSML. This novel echocardiographic association may help clinicians distinguish NSML from NS in ambiguous cases. Early distinction between the two may be important, as syndrome-specific therapies may become available in the near future. This study may encourage further research into genotype-phenotype associations in other forms of HCM.

Compound heterozygosity for PTPN11 variants in a subject with Noonan syndrome provides insights into the mechanism of SHP2-related disorders.

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.

Phosphatase-independent functions of SHP2 and its regulation by small molecule compounds.

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.

Familial LEOPARD Syndrome With Hypertrophic Cardiomyopathy.

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.

Tyrosyl phosphorylation of PZR promotes hypertrophic cardiomyopathy in PTPN11-associated Noonan syndrome with multiple lentigines.

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.

Therapeutic potential of targeting SHP2 in human developmental disorders and cancers.

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.

Is there still a role for nuchal translucency measurement in the changing paradigm of first trimester screening?

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 95th and 99th percentile and 62% for fetuses with NT≥99th 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.

Cardiac manifestations and gene mutations of patients with RASopathies in Taiwan.

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.

RAF1 variant in a patient with Noonan syndrome with multiple lentigines and craniosynostosis.

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.