Hypertrophic obstructive cardiomyopathy as a manifestation of a cardiocutaneous syndrome (Noonan syndrome)

Summary The case of a 50-year-old patient with hypertrophic obstructive cardiomyopathy is reported. The patient demonstrated somatic signs of the Turner phenotype, but a cytogenetically normal karyotype was shown. These findings were compatible with the diagnosis of Noonan syndrome. The most commonly diagnosed cardiac disease in this syndrome is pulmonary stenosis, followed by hypertrophic cardiomyopathy. The patient's prognosis is limited by the natural history or the typical complications of the underlying cardiac lesion.Abbreviations EC echocardiography - H(O)CM hypertrophic (obstructive) cardiomyopathy - NS Noonan syndrome - SAM systolic anterior motion - MRT magnetic resonance tomogram - LH luteinizing hormone - FSH follicle-stimulating hormone     

Neurofibromatosis/Noonan phenotype: a variable feature of type 1 neurofibromatosis

Since January 1989 we have ascertained patients with neurofibromatosis type 1 (NFl) as part of our genetic register in the North West of England. This register has now identified 453 affected cases from 235 families. The first 94 individuals were specifically examined for features of the Noonan phenotype. This was present in 12/94 sequentially identified individuals with NFl, including six individuals from three families. However, three cases occurred in a further family, where Noonan syndrome appeared to segregate separately from NFl. We have provided evidence for the chance association of Noonan syndrome and NFl and that the Noonan phenotype occurs as a feature in some NFl families. However, there is now little evidence of a separate NFl/Noonan syndrome entity or of NFl features occurring in classical Noonan syndrome.     

SOS1: a new player in the Noonan-like/multiple giant cell lesion syndrome

Noonan-like/multiple giant cell lesion syndrome is a rare condition with phenotypic overlap with Noonan syndrome (NS) and cherubism. PTPN11 gene mutations were described in several individuals with this phenotype, and it is recently considered as a variant phenotype of NS. Gain-of-function mutations in the SOS1 gene were recently described as the second major cause of NS. Here, we report for the first time the involvement of SOS1 gene in a family with the Noonan-like/multiple giant cell lesion phenotype.     

Genetic landscape of RASopathies in Chinese: Three decades' experience in Hong Kong

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.     

Noonan syndrome and neurofibromatosis type I in a family with a novel mutation in NF1

Noonan syndrome (NS) and neurofibromatosis type I (NF1) belong to a group of clinically related disorders that share a common pathogenesis, dysregulation of the RAS‐MAPK pathway. NS is characterized by short stature, heart defect, pectus deformity and facial dysmorphism, whereas skin manifestations, skeletal defects, Lisch nodules and neurofibromas are characteristic of NF1. Both disorders display considerable clinical variability. Features of NS have been observed in individuals with NF1 –a condition known as neurofibromatosis–Noonan syndrome (NFNS). The major gene causing NFNS is NF1. Rarely, a mutation in PTPN11 in addition to an NF1 mutation is present. We present the clinical and molecular characterization of a family displaying features of both NS and NF1, with complete absence of neurofibromas. To investigate the etiology of the phenotype, mutational analysis of NF1 was conducted, revealing a novel missense mutation in exon 24, p.L1390F, affecting the GAP‐domain. Additional RAS‐MAPK pathway genes were examined, but no additional mutations were identified. We confirm that NF1 mutations are involved in the etiology of NFNS. Furthermore, based on our results and previous studies we suggest that evaluation of the GAP‐domain of NF1 should be prioritized in NFNS.     

PTPN11 mutations in Noonan syndrome type I: detection of recurrent mutations in exons 3 and 13

We surveyed 16 subjects with the clinical diagnosis of Noonan Syndrome (NS1) from 12 families and their relevant family members for mutations in PTPN11/SHP2 using direct DNA sequencing. We found three different mutations among five families. Two unrelated subjects shared the same de novo missense substitution in exon 13 (S502T); an additional two unrelated families had a mutation in exon 3 (Y63C); and one subject had the amino acid substitution Y62D, also in exon 3. None of the three mutations were present in ethnically matched controls. In the mature protein model, the exon 3 mutants and the exon 13 mutant amino acids cluster at the interface between the N' SH2 domain and the phosphatase catalytic domain. Six of eight subjects with PTPN11/SHP2 mutations had pulmonary valve stenosis while no mutations were identified in those subjects (N = 4) with hypertrophic cardiomyopathy. An additional four subjects with possible Noonan syndrome were evaluated, but no mutations in PTPN11/SHP2 were identified. These results confirm that mutations in PTPN11/SHP2 underlie a common form of Noonan syndrome, and that the disease exhibits both allelic and locus heterogeneity. The observation of recurrent mutations supports the hypothesis that a special class of gain-of-function mutations in SHP2 give rise to Noonan syndrome.     

Molecular Diversity and Associated Phenotypic Spectrum of Germline CBL Mutations

Noonan syndrome (NS) is a relatively common developmental disorder with a pleomorphic phenotype. Mutations causing NS alter genes encoding proteins involved in the RAS‐MAPK pathway. We and others identified Casitas B‐lineage lymphoma proto‐oncogene (CBL), which encodes an E3‐ubiquitin ligase acting as a tumor suppressor in myeloid malignancies, as a disease gene underlying a condition clinically related to NS. Here, we further explored the spectrum of germline CBL mutations and their associated phenotype. CBL mutation scanning performed on 349 affected subjects with features overlapping NS and no mutation in NS genes allowed the identification of five different variants with pathological significance. Among them, two splice‐site changes, one in‐frame deletion, and one missense mutation affected the RING domain and/or the adjacent linker region, overlapping cancer‐associated defects. A novel nonsense mutation generating a v‐Cbl‐like protein able to enhance signal flow through RAS was also identified. Genotype–phenotype correlation analysis performed on available records indicated that germline CBL mutations cause a variable phenotype characterized by a relatively high frequency of neurological features, predisposition to juvenile myelomonocytic leukemia, and low prevalence of cardiac defects, reduced growth, and cryptorchidism. Finally, we excluded a major contribution of two additional members of the CBL family, CBLB and CBLC, to NS and related disorders.     

Co-occurring SHOC2 and PTPN11 mutations in a patient with severe/complex Noonan syndrome-like phenotype

Noonan syndrome (NS) is a heterogeneous disorder caused by activating mutations in the RAS-MAPK signaling pathway. It is associated with variable clinical expression including short stature, congenital heart defect, unusual pectus deformity, and typical facial features and the inheritance is autosomal dominant. Here, we present a clinical and molecular characterization of a patient with Noonan-like syndrome with loose anagen hair phenotype and additional features including mild psychomotor developmental delay, osteoporosis, gingival hyperplasia, spinal neuroblastoma, intrathoracic extramedullary hematopoiesis, and liver hemangioma. Mutation analysis of PTPN11, SOS1, RAF1, KRAS, BRAF, MEK1, MEK2, NRAS, and SHOC2 was conducted, revealing a co-occurrence of two heterozygous previously identified mutations in the index patient. The mutation SHOC2 c.4A > G; p.Ser2Gly represents a de novo mutation, whereas, PTPN11 c.1226G > C; p.Gly409Ala was inherited from the mother and also identified in the brother. The mother and the brother present with some NS manifestations, such as short stature, delayed puberty, keratosis pilaris, café-au-lait spots, refraction error (mother), and undescended testis (brother), but no NS facial features, supporting the notion that the PTPN11 p.Gly409Ala mutation leads to a relatively mild phenotype. We propose that, the atypical phenotype of the young woman with NS reported here is an additive effect, where the PTPN11 mutation acts as a modifier. Interestingly, co-occurrence of RAS-MAPK mutations has been previously identified in a few patients with variable NS or neurofibromatosis-NS phenotypes. Taken together, the results suggest that co-occurrence of mutations or modifying loci in the RAS-MAPK pathway may contribute to the clinical variability observed among NS patients.     

Clinical manifestations in patients with SOS1 mutations range from Noonan syndrome to CFC syndrome

Noonan syndrome (NS) and cardio-facio-cutaneous (CFC) syndrome are autosomal dominant disorders characterized by heart defects, facial dysmorphism, ectodermal abnormalities, and mental retardation. There is a significant clinical overlap between NS and CFC syndrome, but ectodermal abnormalities and mental retardation are more frequent in CFC syndrome. Mutations in PTPN11 and KRAS have been identified in patients with NS and those in KRAS, BRAF and MAP2K1/2 have been identified in patients with CFC syndrome, establishing a new role of the RAS/MAPK pathway in human development. Recently, mutations in the son of sevenless gene (SOS1) have also been identified in patients with NS. To clarify the clinical spectrum of patients with SOS1 mutations, we analyzed 24 patients with NS, including 3 patients in a three-generation family, and 30 patients with CFC syndrome without PTPN11, KRAS, HRAS, BRAF, and MAP2K1/2 (MEK1/2) mutations. We identified two SOS1 mutations in four NS patients, including three patients in the above-mentioned three-generation family. In the patients with a CFC phenotype, three mutations, including a novel three amino-acid insertion, were identified in one CFC patient and two patients with both NS and CFC phenotypes. These three patients exhibited ectodermal abnormalities, such as curly hair, sparse eyebrows, and dry skin, and two of them showed mental retardation. Our results suggest that patients with SOS1 mutations range from NS to CFC syndrome.     

Neuropsychological features in RASopathies: A pilot study on parent training program involving families of children with Noonan syndrome

Noonan syndrome (NS) is a clinical variable multisystem disorder caused by mutations in genes encoding proteins involved in the RAS/mitogen-activated protein kinase signaling pathway. NS is characterized by a distinctive facies, short stature, and congenital heart defects. Psychomotor delay, learning difficulties, and social deficits are also common. Furthermore, behavioral and attention problems can be reckoned as a key symptom in NS, with functioning resembling the patterns observed in attention deficit hyperactivity disorder (ADHD). The complex behavioral phenotype has great impact on the quality of life and raises demanding management issues also for patients' families. Parent management training (PMT) is recommended as first-line treatment for ADHD; however, no study has been performed to test the efficacy of PMT in NS, thus far. The aim of this pilot study is the implementation and evaluation of a PMT dedicated to NS families. Parents of seven children with NS were recruited and underwent to a 10-session PMT. Three different questionnaires were administered to both parents: Conners Parent Rating Scales, Parenting Stress Index Short Form (PSI-SF), and Alabama Parenting Questionnaire (APQ). Our findings on this first small cohort of families indicate that positive perception and satisfaction about the child and the interaction with him increased in mothers after the intervention, as measured respectively by PSI-SF difficult child (DC) and PSI-SF parent–child dysfunctional interaction (PCDI), while mothers' level of stress decreased after the PMT, as indicated by PSI-SF total scores. Furthermore, APQ positive parenting, which measures behaviors of positive relationship with the child, increased in mothers after the intervention. Statistical analysis on fathers' questionnaires did not show significant differences after the PMT sessions. This pilot study suggests that PMT is a promising intervention for parents of NS children with behavioral and ADHD symptoms. Changes in mothers' attitudes and distress indicate that behaviorally oriented programs may help parents to manage with NS phenotype.     

Multiple giant cell lesions in patients with Noonan syndrome and cardio-facio-cutaneous syndrome

Noonan syndrome (NS) and cardio-facio-cutaneous syndrome (CFCS) are related developmental disorders caused by mutations in genes encoding various components of the RAS-MAPK signaling cascade. NS is associated with mutations in the genes PTPN11, SOS1, RAF1, or KRAS, whereas CFCS can be caused by mutations in BRAF, MEK1, MEK2, or KRAS. The NS phenotype is rarely accompanied by multiple giant cell lesions (MGCL) of the jaw (Noonan-like/MGCL syndrome (NL/MGCLS)). PTPN11 mutations are the only genetic abnormalities reported so far in some patients with NL/MGCLS and in one individual with LEOPARD syndrome and MGCL. In a cohort of 75 NS patients previously tested negative for mutations in PTPN11 and KRAS, we detected SOS1 mutations in 11 individuals, four of whom had MGCL. To explore further the relevance of aberrant RAS-MAPK signaling in syndromic MGCL, we analyzed the established genes causing CFCS in three subjects with MGCL associated with a phenotype fitting CFCS. Mutations in BRAF or MEK1 were identified in these patients. All mutations detected in these seven patients with syndromic MGCL had previously been described in NS or CFCS without apparent MGCL. This study demonstrates that MGCL may occur in NS and CFCS with various underlying genetic alterations and no obvious genotype-phenotype correlation. This suggests that dysregulation of the RAS-MAPK pathway represents the common and basic molecular event predisposing to giant cell lesion formation in patients with NS and CFCS rather than specific mutation effects.     

Clinical and molecular aspects of an informative family with neurofibromatosis type 1 and Noonan phenotype

Neurofibromatosis-Noonan syndrome (NFNS) has been described as a unique phenotype, combining manifestations of neurofibromatosis type 1 (NF1) and Noonan syndrome, which are separate syndromes. Potential etiologies of NFNS include a discrete syndrome of distinct etiology, co-segregation of two mutated common genes, variable clinical expressivity of NF1, and/or allelic heterogeneity. We present an informative family with an unusual NF1 mutation with variable features of NF1 and Noonan syndrome. We hypothesize that an NF1 mutant allele can lead to diagnostic manifestations of Noonan syndrome, supporting the hypothesis that NF1 allelic heterogeneity causes NFNS.     

Activating Mutations Affecting the Dbl Homology Domain of SOS2 Cause Noonan Syndrome

The RASopathies constitute a family of autosomal‐dominant disorders whose major features include facial dysmorphism, cardiac defects, reduced postnatal growth, variable cognitive deficits, ectodermal and skeletal anomalies, and susceptibility to certain malignancies. Noonan syndrome (NS), the commonest RASopathy, is genetically heterogeneous and caused by functional dysregulation of signal transducers and regulatory proteins with roles in the RAS/extracellular signal‐regulated kinase (ERK) signal transduction pathway. Mutations in known disease genes account for approximately 80% of affected individuals. Here, we report that missense mutations altering Son of Sevenless, Drosophila, homolog 2 (SOS2), which encodes a RAS guanine nucleotide exchange factor, occur in a small percentage of subjects with NS. Four missense mutations were identified in five unrelated sporadic cases and families transmitting NS. Disease‐causing mutations affected three conserved residues located in the Dbl homology (DH) domain, of which two are directly involved in the intramolecular binding network maintaining SOS2 in its autoinhibited conformation. All mutations were found to promote enhanced signaling from RAS to ERK. Similar to NS‐causing SOS1 mutations, the phenotype associated with SOS2 defects is characterized by normal development and growth, as well as marked ectodermal involvement. Unlike SOS1 mutations, however, those in SOS2 are restricted to the DH domain.     

Cardio–facio–cutaneous syndrome phenotype in an individual with an interstitial deletion of 12q: Identification of a candidate region for CFC syndrome

We report on a 19‐month‐old girl who presented with the phenotype of cardio–facio–cutaneous (CFC) syndrome including characteristic minor facial anomalies, cardiac defect, ectodermal anomalies, and developmental delay. Cytogenetic analysis showed the presence of an interstitial deletion of one chromosome 12, del(12)(q21.2q22), confirmed by fluorescence in situ hybridization with chromosome band specific probes. Controversy exists as to whether CFC and Noonan syndrome (NS) are distinct disorders, a contiguous gene syndrome, or allelic variants. The identification of the del(12) in this patient, in a region distinct from the putative NS locus, supports the view that CFC is a genetically distinct condition from NS. In addition, this implicates the region 12q21.2→q22 as a candidate region for the gene(s) causing CFC syndrome. Am. J. Med. Genet. 93:219–222, 2000. © 2000 Wiley‐Liss, Inc.     

Noonan syndrome and aortic coarctation

Congenital heart defect (CHD) is present in half of the propositi with Noonan syndrome (NS). Aortic coarctation (AC) is rarely seen in NS, since only three male patients with NS and AC have been previously reported. On the other hand, AC is common in the Ullrich-Turner syndrome, an aneuploidy disorder and not a mendelian syndrome. In order to evaluate if AC is truly rare in patients with NS, we reviewed our series of 184 propositi with NS and CHD. AC was diagnosed in 16 (8.7%) patients. There were 11 males and 5 females. All had normal chromosomes. Clinical characteristics of the patients are described. Familial occurrence was detected in one girl with NS and AC whose mother and sibs also had NS, but different form of CHDs. Thus, AC is more frequent in NS than previously reported. Am. J. Med. Genet. 80:160–162, 1998. © 1998 Wiley-Liss, Inc.     

6例Noonan综合征患者临床特点及重组人生长激素治疗效果分析

目的 本研究将总结6例Noonan综合征(NS)患者的临床特点、基因诊断结果及对重组人生长激素(rh GH)治疗的反应。方法 回顾性总结2009年5月至2015年8月在北京协和医院内分泌科矮小门诊的6例NS患者的临床特点。5例以0.1 IU/(kg·d)为起始剂量应用rh GH,进行定期随访,并与年龄/性别相匹配的同期应用rh GH的10例特纳综合征(TS)和10例生长激素缺乏症(GHD)患者进行比较。结果 6例患者均存在NS的典型临床表现;5例经rh GH治疗后,年生长速度显著增加(P0.01);NS与TS患者rh GH疗效相似,随访各点均无显著性差异;但GHD患者相比,在应用rh GH后疗效欠佳;不良事件:2例NS在随访期出现亚临床甲状腺功能减低。结论 NS患者具有典型的临床表现,基因检查有助于明确诊断,rh GH治疗有显著疗效及较高的安全性。     

Delineation of dominant and recessive forms of LZTR1-associated Noonan syndrome

Noonan syndrome (NS) is characterised by distinctive facial features, heart defects, variable degrees of intellectual disability and other phenotypic manifestations. Although the mode of inheritance is typically dominant, recent studies indicate LZTR1 may be associated with both dominant and recessive forms. Seeking to describe the phenotypic characteristics of LZTR1-associated NS, we searched for likely pathogenic variants using two approaches. First, scrutiny of exomes from 9624 patients recruited by the Deciphering Developmental Disorders (DDDs) study uncovered six dominantly-acting mutations (p.R97L; p.Y136C; p.Y136H, p.N145I, p.S244C; p.G248R) of which five arose de novo, and three patients with compound-heterozygous variants (p.R210*/p.V579M; p.R210*/p.D531N; c.1149+1G>T/p.R688C). One patient also had biallelic loss-of-function mutations in NEB, consistent with a composite phenotype. After removing this complex case, analysis of human phenotype ontology terms indicated significant phenotypic similarities (P = 0.0005), supporting a causal role for LZTR1. Second, targeted sequencing of eight unsolved NS-like cases identified biallelic LZTR1 variants in three further subjects (p.W469*/p.Y749C, p.W437*/c.-38T>A and p.A461D/p.I462T). Our study strengthens the association of LZTR1 with NS, with de novo mutations clustering around the KT1-4 domains. Although LZTR1 variants explain ~0.1% of cases across the DDD cohort, the gene is a relatively common cause of unsolved NS cases where recessive inheritance is suspected.     

Congenital heart defects in Noonan syndrome: Diagnosis,management, and treatment

Noonan syndrome is a pleomorphic genetic disorder, in which a high percentage of affected individuals have cardiovascular involvement, most prevalently various forms of congenital heart disease (i.e., pulmonary valve stenosis, septal defects, left‐sided lesions, and complex forms with multiple anomalies). Care includes attentiveness to several comorbidities, some directly impacting cardiac management (bleeding diatheses and lymphatic anomalies). More than 50% of patients with Noonan syndrome harbor PTPN11 pathogenic variation, which results in hyperactivation of RAS/mitogen‐activated protein kinase signaling. Several other disease genes with similar biological effects have been uncovered for NS and phenotypically related disorders, collectively called the RASopathies. Molecular diagnosis with gene resequencing panels is now widely available, but phenotype variability and in some cases, subtlety, continues to make identification of Noonan syndrome difficult. Until genetic testing becomes universal for patients with congenital heart disease, alertness to Noonan syndrome's broad clinical presentations remains crucial. Genotype–phenotype associations for Noonan syndrome enable better prognostication for affected patients when a molecular diagnosis is established. We still lack Noonan syndrome‐specific treatment; however, newly developed anticancer RAS pathway inhibitors could fill that gap if safety and efficacy can be established for indications such as pulmonary valve stenosis.     

The RRAS2 pathogenic variant p.Q72L produces severe Noonan syndrome with hydrocephalus: A case report

Noonan syndrome (NS) is the most common disease among RASopathies, characterized by short stature, distinctive facial features, congenital cardiac defects, and variable developmental delay. NS rarely presents with overt neurologic manifestations, in particular hydrocephalus. Recent evidence suggests that pathogenic variants in the gene RRAS2 are a rare cause of NS. Specifically, an RRAS2 pathogenic variant, p.Q72L, may be particularly severe, manifesting with lethal neurologic findings. Here, we report a NS patient with documented p.Q72L variant in RRAS2. The patient was identified in utero to have hydrocephalus and a Dandy Walker malformation. Postnatal examination revealed multiple dysmorphic features, some reminiscent of NS including low-set posteriorly rotated ears, redundant nuchal skin, widely spaced nipples, and cryptorchidism. Despite suspicion of NS, results of a 14-gene Noonan syndrome panel (Invitae) were negative. Follow-up rapid whole exome sequencing revealed a de novo p.Q72L variant in RRAS2, a poorly studied gene recently identified as a cause of NS. The patient herein reported brings to three the total number of cases reported with the RRAS2 p.Q72L pathogenic variant. All three documented patients presented with a particularly fulminant course of NS, which included hydrocephalus. RRAS2, specifically p.Q72L, should be considered in severe NS cases with neurologic manifestations.     

Novel BRAF mutation in a patient with LEOPARD syndrome and normal intelligence

Noonan syndrome (NS) and related disorders are caused by mutations in various genes encoding molecules involved in the RAS–MAPK signalling cascade. There are strong genotype–phenotype correlations. BRAF is the major gene for cardio-facio-cutaneous syndrome (CFCS), and usually patients with a BRAF mutation have significant cognitive impairment. We report on a patient with LEOPARD syndrome and normal intelligence who was found to carry a novel sequence change in BRAF. The mutation p.L245F was demonstrated to be de novo with no evidence of somatic mosaicism. This observation illustrates that the phenotypic spectrum caused by BRAF mutations is broader than previously assumed and that mental retardation is not necessarily associated. We speculate that the impact of p.L245F on BRAF protein function differs either qualitatively or quantitatively from those mutations associated with CFCS.