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

Noonan syndrome (NS) is an autosomal dominant disorder characterized by clinical and genetic heterogeneity. It belongs to a wider group of pathologies, known as Rasopathies, due to the implication of genes encoding components of the Ras/MAPK signalling pathway. Recording the genetic alterations across populations helps assessing specific features to specific genes which is essential for better disease's recognition, prognosis and monitoring. Herein, we report the clinical and molecular data of a Greek cohort comprising of 86 NS or NS-like patients admitted at a single tertiary Centre in Athens, Greece. The analysis was performed using Sanger and next-generation sequencing, comprising 14 different genes. The mutational rates of the confirmed NS-associated genes in the Greek NS population are as follows: PTPN11 32.5%; RIT1 5.8%; SOS1 4.7%; BRAF 1.2%; CBL 1.2%; KRAS 1.2%; MAP2K1 1.2%; RAF1 1.2%; SHOC2 1.2%, corresponding to 50% of positivity in total NS population. The genotype-phenotype analysis showed statistically significant differences in craniofacial dysmorphisms (p = 0.005) and pulmonary valve stenosis (PS) (p < 0.001) frequencies between patients harbouring a pathogenic variant and patients without pathogenic variant in any of the tested genes. Patients with at least a pathogenic variant had 6.71 times greater odds to develop PS compared to pathogenic variant-negative patients (OR = 6.71, 95%; CI = (2.61, 17.27)). PTPN11 positive patients showed higher frequency of epicanthal folds (p = 0.004), ptosis (p = 0.001) and coarseness (p = 0.001) and lower frequency of neurological findings (p = 0.006), compared to patients carrying pathogenic variants in other genes. CONCLUSION: Craniofacial dysmorphism and PS prevail among pathogenic variant positive compared to pathogenic variant negative NS and NS-like patients while neurological defects are less common in PTPN11-affected NS patients compared to patients harbouring pathogenic variants in other genes. The significant prevalence of the Ras/MAPK pathogenic variants (17.4%), other than PTPN11, in Greek NS patients, highlights the necessity of a wider spectrum of molecular diagnosis. WHAT IS KNOWN: • Noonan syndrome (NS) has been associated with pathogenic variants in molecules-components of the Ras/MAPK pathway. • Clinical and genetic description of NS patients worldwide helps establishing personalized monitoring. WHAT IS NEW: • NS and NS-like mutational rate in Greece reaches 50% with pathogenic variants identified mostly in PTPN11 (32.5%), RIT1 (6%) and SOS1 (4.7%) genes. • The risk for pulmonary stenosis increases 6.71-fold in NS patients with a pathogenic variant compared to patients without genetic alterations.

High resolution Chromosomal Microarray Analysis (CMA) enhances the genetic profile of pediatric B-cell Acute Lymphoblastic Leukemia patients.

Acute Lymphoblastic Leukemia (ALL) is a malignancy of the immature lymphoid cells mainly associated with numerical and structural chromosomal aberrations. The current standard for profiling the diverse genetic background comprises a combination of conventional karyotype and FISH analysis for the most common translocations, albeit with many limitations. Chromosomal Microarray Analysis (CMA) is a high throughput whole genome method that is gradually implemented in routine clinical practice, but not many studies have compared the two methods. Here we aim to investigate the added benefits of utilizing the high resolution 2 x 400 K G3 CGH + SNP CMA platform in routine diagnostics of pediatric ALL. From the 29 bone marrow samples that were analyzed, CMA identified clinically relevant findings in 83%, while detecting chromosomal aberrations in 75% of the patients with normal conventional karyotype. The most common finding was hyperdiploidy (20%), and the most common submicroscopic aberration involved CDKN2A/B genes. The smallest aberration detected was a 9 kb partial NF1 gene duplication. The prognosis of the patients when combining conventional cytogenetics and CMA was either changed or enhanced in 66% of the cases. A rare duplication possibly indicative of a cryptic ABL1-NUP214 fusion gene was found in one patient. We conclude that CMA, when combined with conventional cytogenetic analysis, can significantly enhance the genetic profiling of patients with pediatric ALL in a routine clinical setting.

Position effect, cryptic complexity, and direct gene disruption as disease mechanisms in de novo apparently balanced translocation cases.

The majority of apparently balanced translocation (ABT) carriers are phenotypically normal. However, several mechanisms were proposed to underlie phenotypes in affected ABT cases. In the current study, whole-genome mate-pair sequencing (WG-MPS) followed by Sanger sequencing was applied to further characterize de novo ABTs in three affected individuals. WG-MPS precisely mapped all ABT breakpoints and revealed three possible underlying molecular mechanisms. Firstly, in a t(X;1) carrier with hearing loss, a highly skewed X-inactivation pattern was observed and the der(X) breakpoint mapped ~87kb upstream an X-linked deafness gene namely POU3F4, thus suggesting an underlying long-range position effect mechanism. Secondly, cryptic complexity and a chromothripsis rearrangement was identified in a t(6;7;8;12) carrier with intellectual disability. Two translocations and a heterozygous deletion disrupted SOX5; a dominant nervous system development gene previously reported in similar patients. Finally, a direct gene disruption mechanism was proposed in a t(4;9) carrier with dysmorphic facial features and speech delay. In this case, the der(9) breakpoint directly disrupted NFIB, a gene involved in lung maturation and development of the pons with important functions in main speech processes. To conclude, in contrast to familial ABT cases with identical rearrangements and discordant phenotypes, where translocations are considered coincidental, translocations seem to be associated with phenotype presentation in affected de novo ABT cases. In addition, this study highlights the importance of investigating both coding and non-coding regions to decipher the underlying pathogenic mechanisms in these patients, and supports the potential introduction of low coverage WG-MPS in the clinical investigation of de novo ABTs.

Application of high-resolution array comparative genomic hybridization in children with unknown syndromic microcephaly.

BackroundMicrocephaly can either be isolated or it may coexist with other neurological entities and/or multiple congenital anomalies, known as syndromic microcephaly. Although many syndromic cases can be classified based on the characteristic phenotype, some others remain uncertain and require further investigation. The present study describes the application of array-comparative genomic hybridization (array-CGH) as a diagnostic tool for the study of patients with clinically unknown syndromic microcephaly.MethodsFrom a cohort of 210 unrelated patients referred with syndromic microcephaly, we applied array-CGH analysis in 53 undiagnosed cases. In all the 53 cases except one, previous standard karyotype was negative. High-resolution 4 × 180K and 1 × 244K Agilent arrays were used in this study.ResultsIn 25 out of the 53 patients with microcephaly among other phenotypic anomalies, array-CGH revealed copy number variations (CNVs) ranging in size between 15 kb and 31.6 Mb. The identified CNVs were definitely causal for microcephaly in 11/53, probably causal in 7/53, and not causal for microcephaly in 7/53 patients. Genes potentially contributing to brain deficit were revealed in 16/53 patients.ConclusionsArray-CGH contributes to the elucidation of undefined syndromic microcephalic cases by permitting the discovery of novel microdeletions and/or microduplications. It also allows a more precise genotype-phenotype correlation by the accurate definition of the breakpoints in the deleted/duplicated regions.

A boy with conduct disorder (CD), attention deficit hyperactivity disorder (ADHD), borderline intellectual disability, and 47,XXY syndrome in combination with a 7q11.23 duplication, 11p15.5 deletion, and 20q13.33 deletion.

BACKGROUND: This is a case with multiple chromosomal aberrations which are likely etiological for the observed psychiatric phenotype consisting of attention deficit hyperactivity and conduct disorders. CASE PRESENTATION: We report on an 11 year-old boy, admitted to the pediatric hospital for behavioral difficulties and a delayed neurodevelopmental trajectory. A cytogenetic analysis and high-resolution microarray comparative genomic hybridization (CGH) analysis was performed. The cytogenetic analysis revealed 47,XYY syndrome, while CGH analysis revealed an additional duplication and two deletions. The 7q11.23 duplication is associated with speech and language delay and behavioral symptoms, a 20q13.33 deletion is associated with autism and early onset schizophrenia and the 11p15.5 microdeletion is associated with developmental delay, autism, and epilepsy. The patient underwent a psychiatric history, physical examination, laboratory testing, and a detailed cognitive, psychiatric, and occupational therapy evaluation which are reported here in detail. CONCLUSIONS: In the case of psychiatric patients presenting with complex genetic aberrations and additional psychosocial problems, traditional psychiatric and psychological approaches can lead to significantly improved functioning. Genetic diagnostic testing can be highly informative in the diagnostic process and may be applied to patients in psychiatry in case of complex clinical presentations.

A dynamic trinucleotide repeat (TNR) expansion in the DMD gene.

Dystrophinopathies are allelic X-linked myopathies caused by large deletions/duplications or small lesions along the DMD gene. An unexpected dynamic trinucleotide (GAA) expansion, ranging from ∼59 to 82 pure GAA repeats, within the DMD intron 62, was revealed to segregate through three family generations. From the pedigree, two female patients were referred for DMD investigation due to chronic myopathy and a muscle biopsy compatible with dystrophinopathy. As the size of the GAA repeat is limited to 11-33 within the general population our findings may provide a novel insight towards a Trinucleotide Repeat Expansion. Whether this TNR has an impact on the reported phenotype remains to be resolved.

Complex preimplantation genetic diagnosis for beta-thalassaemia, sideroblastic anaemia, and human leukocyte antigen (HLA)-typing.

Preimplantation genetic diagnosis (PGD) to select histocompatible siblings to facilitate curative haematopoeitic stem-cell transplantation (HSCT) is now an acceptable option in the absence of an available human leukocyte antigen (HLA) compatible donor. We describe a case where the couple who requested HLA-PGD, were both carriers of two serious haematological diseases, beta-thalassaemia and sideroblastic anaemia. Their daughter, affected with sideroblastic anaemia, was programmed to have HSCT. A multiplex-fluorescent-touchdown-PCR protocol was optimized for the simultaneous amplification of: the two HBB-gene mutated regions (c.118C> T, c.25-26delAA), four short tandem repeats (STRs) in chr11p15.5 linked to the HBB gene, the SLC25A38 gene mutation (c.726C > T), two STRs in chr3p22.1 linked to the SLC25A38 gene, plus eleven informative STRs for HLA-haplotyping (chr6p22.1-21.3). This was followed by real-time nested PCR and high-resolution melting analysis (HRMA) for the detection of HBB and SLC25A38 gene mutations, as well as the analysis of all STRs on an automatic genetic analyzer (sequencer). The couple completed four clinical in vitro fertilization (IVF)/PGD cycles. At least one matched unaffected embryo was identified and transferred in each cycle. A twin pregnancy was established in the fourth PGD cycle and genotyping results at all loci were confirmed by prenatal diagnosis. Two healthy baby girls were delivered at week 38 of pregnancy. The need to exclude two familial disorders for HLA-PGD is rarely encountered. The methodological approach described here is fast, accurate, clinically-validated, and of relatively low cost.

TAF1 Variants Are Associated with Dysmorphic Features, Intellectual Disability, and Neurological Manifestations.

We describe an X-linked genetic syndrome associated with mutations in TAF1 and manifesting with global developmental delay, intellectual disability (ID), characteristic facial dysmorphology, generalized hypotonia, and variable neurologic features, all in male individuals. Simultaneous studies using diverse strategies led to the identification of nine families with overlapping clinical presentations and affected by de novo or maternally inherited single-nucleotide changes. Two additional families harboring large duplications involving TAF1 were also found to share phenotypic overlap with the probands harboring single-nucleotide changes, but they also demonstrated a severe neurodegeneration phenotype. Functional analysis with RNA-seq for one of the families suggested that the phenotype is associated with downregulation of a set of genes notably enriched with genes regulated by E-box proteins. In addition, knockdown and mutant studies of this gene in zebrafish have shown a quantifiable, albeit small, effect on a neuronal phenotype. Our results suggest that mutations in TAF1 play a critical role in the development of this X-linked ID syndrome.

Are ALOX5AP gene SNPs a risk or protective factor for stroke?

ALOX5AP (5-lipoxygenase) has been recognized as a susceptibility gene for stroke. Using a case-control design, the whole coding and adjoining intronic regions of ALOX5AP were sequenced to study the role of SNPs and their interplay with other risk factors in Greek patients with stroke. Patients (n=213) were classified by the Trial of Org 10172 in Acute Stroke Treatment (TOAST). Their mean age of was 58.9 ± 14.64, comprising 145 males. The control group consisted of 210 subjects, ethnicity, sex and age matched, with no stroke history. Risk factors (hyperlipidemia, hypertension, atrial fibrillation, migraine, CAD, diabetes, smoking and alcohol consumption) were assessed as confounding factors and comparisons were done using logistic regression analysis. SNPs rs4769055, rs202068154 and rs3803277 located in intronic regions of the gene and according to in silico programs EX_SKIP and HSF possibly affecting splicing of exons 1 and 2 of ALOX5AP, showed significantly different frequencies between patients and controls. The genotype frequencies of rs4769055: AA, of rs202068154: AC and of rs3803277: CA were significantly higher (p<0.001, 0.058) in controls than in patients. The results were indicative of a protective role of the three SNPs either in homozygosity or heterozygosity for MAF and more specifically rs3803277: CA/AA genotypes were protective against SVO stroke subtype.

Mutation screening in the Greek population and evaluation of NLGN3 and NLGN4X genes causal factors for autism.

Molecular and neurobiological evidence for the involvement of neuroligins (particularly NLGN3 and NLGN4X genes) in autistic disorder is accumulating. However, previous mutation screening studies on these two genes have yielded controversial results. The present study explores, for the first time, the contribution of NLGN3 and NLGN4X genetic variants in Greek patients with autistic disorder. We analyzed the full exonic sequence of NLGN3 and NLGN4X genes in 40 patients strictly fulfilling the Diagnostic and Statistical Manual of Mental Disorders, 4th ed. criteria for autistic disorder. We identified nine nucleotide changes in NLGN4X--one probable causative mutation (p.K378R) previously reported by our research group, one novel variant (c.-206G>C), one nonvalidated single nucleotide polymorphism (SNP, rs111953947), and six known human SNPs reported in the SNP database--and one known human SNP in NLGN3 also reported in the SNP database. The variants identified are expected to be benign. However, they should be investigated in the context of variants in interacting cellular pathways to assess their contribution to the etiology of autism.

Array comparative genomic hybridization as a clinical diagnostic tool in syndromic and nonsyndromic congenital heart disease.

BACKGROUND: Congenital heart diseases (CHDs) are often associated with other congenital anomalies, dysmorphic features, and developmental delay, and only a few cases of chromosomal abnormalities are detected by conventional cytogenetic techniques. The microarray comparative genomic hybridization (CGH) analysis allows the identification of submicroscopic genomic rearrangements. METHODS: During the past 3 y, 55 of 330 patients referred for array CGH had CHD of unknown etiology plus at least one additional indication of abnormal chromosomal phenotype. High-resolution 1 × 244 K or 4 × 180 K Agilent arrays were used in this study (average resolution 7-13 kb). RESULTS: Copy-number variations were detected in 37 of 55 patients, and in 29 of 37 patients there were genes that have been associated with CHD. All 37 patients had at least one additional phenotypic abnormality: 30 of 37 had one or more other congenital anomalies, 23 of 37 had dysmorphic features, 16 of 37 had intellectual disability, 13 of 37 had abnormal magnetic resonance imaging, 10 of 37 had hypotonia, and 7 of 37 had seizures. In 9 of 55 patients, unexpected genomic rearrangements in relation to their phenotype were identified. CONCLUSION: In patients with CHD and at least one additional indication of abnormal chromosomal phenotype, array CGH analysis could detect possible submicroscopic chromosomal abnormalities and provide proper genetic counseling.

Psychomotor development of children born after preimplantation genetic diagnosis and parental stress evaluation.

BACKGROUND: The increasing number of children conceived following preimplantation genetic diagnosis (PGD) necessitates the evaluation of their motor and cognitive development. The primary study objective was to evaluate the physical, developmental, and neurological outcome of children born after PGD in Greece. In addition, the secondary study objective was to compare the stress levels regarding parental roles between parents of PGD children and those of naturally conceived children. METHODS: A cross-sectional study design was applied. The study population consisted of 31 children (aged 2 months to 7.5 years) born after PGD analysis and their parents. The developmental evaluation of children included a detailed physical evaluation and cognitive assessment with the Bayley Scales of Infant Development. The parent stress index was applied to evaluate comparative parental stress levels between those parents of PGD children and those of naturally conceived healthy children. RESULTS: High rates of caesarean deliveries, increased incidence of prematurity, multiples and low-birth weight were observed among the 31 PGD children. Overall, 24 of the 31 PGD children had cognitive skills within normal range [general developmental quotient (GDQ): 86-115], while 6 children had lower levels of cognitive skills (GDQ<85). With regard to parental stress, PGD parents reported lower levels of parenting stress as compared to parents of naturally conceived children (P<0.01). CONCLUSIONS: The enhanced frequency of poor cognitive and motor skills as well as low parental stress necessitates early detection and intervention for developmental delays among PGD children.

Sertoli cell tumor and gonadoblastoma in an untreated 29-year-old 46,XY phenotypic male with Frasier syndrome carrying a WT1 IVS9+4C>T mutation.

OBJECTIVE: Frasier syndrome (FS) phenotype in 46,XY patients usually consists of female external genitalia, gonadal dysgenesis, high risk of gonadoblastoma and the development of end stage renal failure usually in the second decade of life. FS is caused by heterozygous de novo intronic splice site mutations of the Wilms' tumor suppressor gene 1 (WT1), although a few cases with typical exonic WT1 Denys-Drash mutations that resemble an FS phenotype have been described. The aim of this study was to present further data on the spectrum of FS phenotypes through the evaluation of a 29-year-old patient with a predominantly male phenotype and coexistence of Sertoli cell tumor and gonadoblastoma. RESULTS: Genetic analysis using standard methods for DNA sequencing confirmed FS due to a WT1 gene mutation, IVS9+4C>T. CONCLUSIONS: This very rare case illustrates the natural course of FS over many years due to the neglect by the patient to address his need for follow-up, while adding further data on the spectrum of FS phenotypes associated with IVS9+4 C>T mutations. The coexistence of the rare Sertoli cell tumor and gonadoblastoma emphasizes that early clinical recognition and molecular identification facilitates appropriate patient management, especially with respect to the high risk of gonadal malignancy.

An unusual case of Cat-Eye syndrome phenotype and extragonadal mature teratoma: review of the literature.

BACKGROUND Cat-Eye syndrome (CES) with teratoma has not been previously reported. We present the clinical and molecular findings of a 9-month-old girl with features of CES and also a palpable midline neck mass proved to be an extragonadal mature teratoma, additionally characterized by array comparative genomic hybridization (aCGH). RESULTS High resolution oligonucleotide-based aCGH confirmed that the supernumerary marker chromosome (SMC) derived from chromosome 22, as was indicated by molecular cytogenetic analysis with fluorescence in situ hybridization (FISH). Additionally, aCGH clarified the size, breakpoints, and gene content of the duplication (dup 22q11.1q11.21; size:1.6 Mb; breakpoints: 15,438,946-17,041,773; hg18). The teratoma tissue was also tested with aCGH, in which the CES duplication was not found, but the analysis revealed three aberrations: del Xp22.3 (108,864-2788,689; 2.7 Mb hg18), dup Yp11.2 (6688,491-7340,982; 0.65 Mb, hg18), and dup Yq11.2q11.23 (12,570,853-27,177,133; 14.61 Mb, hg18). These results indicated 46 XY (male) karyotype of the teratoma tissue, making this the second report of mature extragonadal teratoma in a female neonate, probably deriving from an included dizygotic twin of opposite sex (fetus in fetu). CONCLUSIONS Our findings extend the phenotypic spectrum of CES syndrome, a disorder with clinical variability, pointing out specific dosage-sensitive genes that might contribute to specific phenotypic features.

Familial Pelizaeus-Merzbacher disease caused by a 320.6-kb Xq22.2 duplication and the pathological findings of a male fetus.

BACKGROUND: Pelizaeus-Merzbacher disease (PMD) is a recessive, X-linked leukoencephalopathy attributed to impaired myelination during central nervous system development, caused by defects in the proteolipid protein 1 (PLP1) gene. PMD presents clinical variability, ranging from the severe connatal form to the classic form. CASES: We report the clinical and molecular findings of two affected males, three carrier females, and an aborted male fetus with familial PMD. The two male probands presented with severe PMD phenotype and intellectual disability. High-resolution oligonucleotide-based array comparative genomic hybridization (aCGH) identified an Xq22.2 duplication of 320.6 kb (102641391-102961998, hg18), including the PLP1 gene and surrounding chromosomal region. Postmortem examination of the aborted fetus at 25 weeks' gestation showed focal subcortical white matter degeneration, focal gliosis, and cerebellar atrophy. CONCLUSIONS: Genotype-phenotype correlation is provided. In the connatal form of PMD, leukodystrophy and cerebellar atrophy can occur antenatally and be established at 25 weeks' gestation. The observation of degenerative brain lesions occurring before the onset of subcortical myelination suggests that the PLP1 gene has a more complex role in human brain development, exceeding its structural function in myelin formation.

MECP2 mutations and clinical correlations in Greek children with Rett syndrome and associated neurodevelopmental disorders.

BACKGROUND: Mutations in the MECP2 gene (methyl-CpG-binding protein-2) are responsible for 60-95% of cases of Rett syndrome (RTT), an X-linked dominant neurodevelopmental disorder affecting mostly girls. Classic RTT is characterized by normal early development followed by psychomotor regression and onset of microcephaly, although variant forms are also observed. MECP2 has also been implicated in variable mental retardation (MR) phenotypes, including X-linked Mental Retardation (XLMR), Fragile-X-like Syndrome (FXS) and Angelman-like (AS) phenotypes. AIM: The aim of the study was: (a) to evaluate the incidence and spectrum of MECP2 mutations in children with RTT and variant MR; (b) to evaluate phenotype-genotype correlations. METHODS: Exons 3-4 were analyzed for mutations in 281 MR patients (aged 13 months-27 years old, 144 males-137 females) consisting of 88 patients referred for RTT and 193 patients referred for AS-like and FXS-like types of MR. Statistical analysis included correlation between classic MECP2-positive and MECP2-negative and variant RTT patients, and frequency of MECP2 mutations in the various categories. RESULTS: Mutations were detected in ≈ 70% of classic and ≈ 21% of variant RTT, respectively. Amongst MR cases, 2.1% carried MECP2 mutations. MECP2-positive females had more problems in ambulation, muscle tone, tremor and ataxia, respiratory disturbances, head growth, hand use and stereotypies. Classic RTT-positive versus negative had significant respiratory and sitting problems and versus variant RTT-positive females ambulatory, hand and stereotypies problems. CONCLUSION: The analysis of the MECP2 gene could provide a diagnostic tool for RTT and non-specific MR research.

Microdeletion and microduplication 17q21.31 plus an additional CNV, in patients with intellectual disability, identified by array-CGH.

The recognition of the 17q21.31 microdeletion and microduplication syndrome has been facilitated by high resolution oligonucleotide array comparative genome hybridization technology (aCGH). Molecular analysis of the 17q21.31 microdeletion/duplication syndrome demonstrated a critical region involving at least six genes, including STH and MAPT. The 17q21.31 microdeletion syndrome has an incidence of 1 in 16,000 births, while the microduplication 17q21.31 has been reported so far in only five patients. In general, phenotypes associated with 17q21.31 microduplication seem to be milder than those associated with the microdeletion. Here, we present four patients who have been referred for genetic evaluation by clinical geneticists due to developmental delay and minor congenital abnormalities. Previous standard karyotypes were negative, while aCGH analysis revealed three patients with 17q21.31 microdeletion and one with the respective microduplication, being the sixth reported case so far. Most importantly one of the microdeletion cases involves only partial MAPT gene deletion while leaving the STH gene intact. Two of our patients, one with the 17q21.31 microdeletion and another with the respective microduplication, carried additional clinically relevant microdeletions (del Xq21.31 and del 15q11.2, respectively), possibly modifying their phenotype.

Phenotypic spectrum of 80 Greek patients referred as Noonan syndrome and PTPN11 mutation analysis: the value of initial clinical assessment.

Noonan syndrome (NS) is a common multiple congenital anomaly entity, the diagnosis of which, on clinical grounds, is based on a comprehensive scoring system in order to select patients for molecular confirmation. Our aim was to evaluate the phenotypic characteristics in the light of PTPN11 mutations. The study revealed 80 patients who were referred with initial indication of NS or Noonan-like syndrome (NLS) and further assessed by a clinical geneticist; 60/80 index patients, mean age 5.9 ± 5.3 years, fulfilled the NS criteria. Molecular analysis of PTPN11 gene (exons and their flanking regions) of the total population revealed mutations in 17/80 patients, all belonging in the group of the patients screened with the scoring system. All mutations were heterozygous missense changes, mostly clustering in exon 3 (8/17), followed by exons 13 (3/17), 8 (2/17), 7 (2/17), 2 (1/17) and 4 (1/17). We conclude that (a) most of our clinically diagnosed NS cases were sporadic (b) PTPN11 analysis should be limited to those fulfilling the relevant NS criteria (c) Cardiovascular evaluation should comprise all NS patients, while pulmonary stenosis, short stature, and thorax deformities prevailed among those with PTPN11 mutations.