Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 2 Caused by a Novel PIGA Variant Not Associated with a Skewed X-Inactivation Pattern.

Germline variants in the phosphatidylinositol glycan class A (PIGA) gene, which is involved in glycosylphosphatidylinositol (GPI) biosynthesis, cause multiple congenital anomalies-hypotonia-seizures syndrome 2 (MCAHS2) with X-linked recessive inheritance. The available literature has described a pattern of almost 100% X-chromosome inactivation in mothers carrying PIGA variants. Here, we report a male infant with MCAHS2 caused by a novel PIGA variant inherited from his mother, who has a non-skewed pattern of X inactivation. Phenotypic evidence supporting the pathogenicity of the variant was obtained by flow-cytometry tests. We propose that the assessment in neutrophils of the expression of GPI-anchored proteins (GPI-APs), especially CD16, should be considered in cases with variants of unknown significance with random X-inactivation in carrier mothers in order to clarify the pathogenic role of PIGA or other gene variants linked to the synthesis of GPI-APs.

Germline variant in Ctcf links mental retardation to Wilms tumor predisposition.

CTCF germline mutations have been related to MRD21. We report the first bilateral Wilms tumor suffered by a MRD21 patient carrying an unreported CTCF missense variant in a zinc finger domain of CTCF protein. We found that germline heterozygous variant I446K became homozygous in the tumor due to a loss of heterozygosity rearrangement affecting the whole q arm on chromosome 16. Our findings propose CTCF I446K variant as a link between MRD21 and Wilms tumor predisposition.

Germline Predisposition to Pediatric Cancer, from Next Generation Sequencing to Medical Care.

Knowledge about genetic predisposition to pediatric cancer is constantly expanding. The categorization and clinical management of the best-known syndromes has been refined over the years. Meanwhile, new genes for pediatric cancer susceptibility are discovered every year. Our current work shares the results of genetically studying the germline of 170 pediatric patients diagnosed with cancer. Patients were prospectively recruited and studied using a custom panel, OncoNano V2. The well-categorized predisposing syndromes incidence was 9.4%. Likely pathogenic variants for predisposition to the patient's tumor were identified in an additional 5.9% of cases. Additionally, a high number of pathogenic variants associated with recessive diseases was detected, which required family genetic counseling as well. The clinical utility of the Jongmans MC tool was evaluated, showing a high sensitivity for detecting the best-known predisposing syndromes. Our study confirms that the Jongmans MC tool is appropriate for a rapid assessment of patients; however, the updated version of Ripperger T criteria would be more accurate. Meaningfully, based on our findings, up to 9.4% of patients would present genetic alterations predisposing to cancer. Notably, up to 20% of all patients carry germline pathogenic or likely pathogenic variants in genes related to cancer and, thereby, they also require expert genetic counseling. The most important consideration is that the detection rate of genetic causality outside Jongmans MC et al. criteria was very low.

Retinoblastoma and mosaic 13q deletion: a case report.

BACKGROUND: Patients with 13q-syndrome are at risk of retinoblastoma when the RB1 gene, located in the chromosomal band 13q14.2, is deleted. This syndrome is frequently associated with congenital malformations and developmental delay, although these signs could be mild. Mosaic 13q-deletion patients have been previously reported in the literature; their phenotype is variable, and they may not be recognized. CASE PRESENTATION: Retinoblastoma diagnosed in a child with 13q-mosaicism confirmed in blood, oral mucosa, healthy retina and retinoblastoma. A second RB1 hit is present exclusively in the retinoblastoma sample (RB1 c.958C>T p.Arg320Ter). Other detected molecular events in retinoblastoma are 6p12.3pter gain and 6q25.3qter loss. Clinical examination is unremarkable except for clinodactyly of the right fifth finger. DISCUSSION AND CONCLUSIONS: We describe a case of mosaic 13q deletion syndrome affected by retinoblastoma. Molecular data obtained from the tumor analysis are similar to previous data available about this malignancy. High clinical suspicion is essential for an adequate diagnosis of mosaic cases.

Prevalence of pathogenic copy number variants among children conceived by donor oocyte.

Development of assisted reproductive technologies to address infertility has favored the birth of many children in the last years. The majority of children born with these treatments are healthy, but some concerns remain on the safety of these medical procedures. We have retrospectively analyzed both the fertilization method and the microarray results in all those children born between 2010 and 2019 with multiple congenital anomalies, developmental delay and/or autistic spectrum disorder (n = 486) referred for array study in our center. This analysis showed a significant excess of pathogenic copy number variants among those patients conceived after in vitro fertilization with donor oocyte with respect to those patients conceived by natural fertilization (p = 0.0001). On the other hand, no significant excess of pathogenic copy number variants was observed among patients born by autologous oocyte in vitro fertilization. Further studies are necessary to confirm these results and in order to identify the factors that may contribute to an increased risk of genomic rearrangements, as well as consider the screening for genomic alterations after oocyte donation in prenatal diagnosis.

Hidden etiology of cerebral palsy: genetic and clinical heterogeneity and efficient diagnosis by next-generation sequencing.

Cerebral palsy (CP) is a heterogeneous neurodevelopmental disorder that causes movement and postural disabilities. Recent research studies focused on genetic diagnosis in patients with CP of unknown etiology. The present study was carried out in 20 families with one family member affected with idiopathic CP. Chromosomal microarray and exome sequencing techniques were performed in all patients. Chromosomal microarray analysis did not show any pathological or probable pathological structural variant. However, the next-generation sequencing study showed a high diagnostic yield. We report 11/20 patients (55%) with different pathogenic or potentially pathogenic variants detected by exome sequencing analysis: five patients with mutations in genes related to hereditary spastic paraplegia, two with mutations in genes related to Aicardi-Goutières syndrome, three with mutations in genes related to developmental/epileptic encephalopathies, and one with a mutation in the PGK1 gene. The accurate and precise patients' selection, the use of a high-throughput genetic platform, the selection of adequate target genes, and the application of rigorous criteria for the clinical interpretation are the most important elements for a good diagnostic performance. Based on our findings, next-generation sequencing should be considered in patients with cryptogenic CP as the first line of genetic workup. IMPACT: Sequencing techniques in CP of uncertain etiology provides a diagnostic yield of 55%. The appropriate selection of cases optimizes the diagnostic yield. NGS facilitate better understanding of new phenotypes of certain genetic diseases.

Recurrent Metabolic Alkalosis in a Cystic Fibrosis Patient: Coexistence with Congenital Chloride Diarrhea.

Metabolic alkalosis is uncommon in infancy. Cystic fibrosis (CF) patients can develop dehydration because of sweat salt or gastrointestinal losses; with the correct salt supplementation, the electrolyte alterations can be reversed. Here, we present a CF patient with recurrent metabolic alkalosis, initially oriented as pseudo-Bartter's syndrome. However, despite accurate treatment, patient needed daily intravenous fluids to maintain homeostasis. An extended study was made, including a urine study that could rule out Bartter's diagnosis. Finally, after a complementary test that included electrolyte stools study and genetic analysis, congenital chloride diarrhea could be diagnosed.

Congenital bilateral absence of the vas deferens (CBAVD): do genetic disorders modify assisted reproductive technologies outcomes? / Ausencia congénita bilateral del conducto deferente: ¿Modifican las alteraciones genéticas los resultados de las tecnicas de reproducción asistida?

OBJECTIVES: To evaluate the impact of common Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene mutations, 5T polymorphism and presence of severe Cystic Fibrosis (CF) on fertility outcomes with Assisted Reproductive Techniques (ART) in patients presenting Congenital Bilateral Absence of Vas Deferens (CBAVD). METHODS: A comparative observational cohort study was performed from 2002 to 2018 with 51 patients with diagnosis of CBAVD. Presence of CFTR mutations and 5T, CF, pregnancy and newborn rates were analyzed. RESULTS: 80.4% percent had some mutation of CFTR gene being ΔF508 the most common (51%). The most frequently described genotype was the 7T/9T (31.4%) with the presence of 5T polymorphism in up to 25.5% of cases. Global newborn rates were 34% in the group using partner spermatozoa. When comparing 5T presence, we observed a decrease in newborn rates when carrying this mutation, without obtaining statistical significance (newborn rate: 5T/non-5T: 7.1/28%, p 0.45). No differences were found when comparing presence of severe CF, common CFTR gene mutations and ICSI-related parameters. CONCLUSION: The analysis of the presence of 5T polymporphism in CBAVD patients may add information when predicting the outcome of assisted reproductive techniques.

OBJETIVOS: Evaluar el impacto de las mutaciones del gen CFTR regulador de la conductancia transmembrana de la fibrosis quística, los polimorfismos 5T y la presencia de fibrosis quística (FQ) grave en los resultados de fertilidad de las técnicas de reproducción asistida en pacientes que presentan ausencia bilateral congénita de conductos deferentes.MÉTODOS: Estudio comparativo observacional de cohortes realizado desde 2002 hasta 2018 con 51 pacientes con el diagnóstico de ausencia bilateral congénita de conductos deferentes. Se analizaron la presencia de mutaciones del gen CFTR y 5T, fibrosis quística y tasas de embarazo y nacimientos. RESULTADOS: 80,4% tenían alguna mutación del CFTR siendo la ΔF508 la más frecuente (51%). El genotipo descrito con mayor frecuencia era 7T/9T (31,4%) con la presencia de polimorfismo 5T en hasta el 25,5% de los casos. Las tasas de nacimientos globales fueron del 34% en el grupo que utilizaba espermatozoides del marido. Cuando se compara la presencia de 5T, observamos una disminución en las tasas de nacimientos en los portadores de esta mutación, sin obtener significación estadística (Tasa de nacimientos 5T/no-5T: 7,1/28%, p=0,45). No se encontraron diferencias en la comparativa entre la presencia de FQ severa, mutaciones comunes del gen CFTR y los parámetros relacionados con la ICSI. CONCLUSIONES: El análisis de la presencia de polimorfismo 5T en los pacientes con ausencia bilateral congénita de conductos deferentes puede añadir información para la predicción de los resultados de las técnicas de reproducción asistida.

Congenital bilateral absence of the vas deferens (cbavd): do Genetic disorders modify assisted reproductive technologies Outcomes? / Ausencia congénita bilateral del conducto deferente: ¿Modifican las alteraciones genéticas los resultados de las tecnicas de reproducción asistida?

OBJECTIVES: To evaluate the impact of common Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene mutations, 5T polymorphism and presence of severe Cystic Fibrosis (CF) on fertility outcomes with Assisted Reproductive Techniques (ART) in patients presenting Congenital Bilateral Absence of Vas Deferens (CBAVD). METHODS: A comparative observational cohort study was performed from 2002 to 2018 with 51 patients with diagnosis of CBAVD. Presence of CFTR mutations and 5T, CF, pregnancy and newborn rates were analyzed. RESULTS: 80.4% percent had some mutation of CFTR gene being DeltaF508 the most common (51%). The most frequently described genotype was the 7T/9T (31.4%) with the presence of 5T polymorphism in up to 25.5% of cases. Global newborn rates were 34% in the group using partner spermatozoa. When comparing 5T presence, we observed a decrease in newborn rates when carrying this mutation, without obtaining statistical significance (newborn rate: 5T/non-5T: 7.1/28%, p 0.45). No differences were found when comparing presence of severe CF, common CFTR gene mutations and ICSI-related parameters. CONCLUSION: The analysis of the presence of 5T polymporphism in CBAVD patients may add information when predicting the outcome of assisted reproductive Techniques

OBJETIVOS: Evaluar el impacto de las mutaciones del gen CFTR regulador de la conductancia transmembrana de la fibrosis quística, los polimorfismos 5T y la presencia de fibrosis quística (FQ) grave en los resultados de fertilidad de las técnicas de reproducción asistida en pacientes que presentan ausencia bilateral congénita de conductos deferentes. MÉTODOS: Estudio comparativo observacional de cohortes realizado desde 2002 hasta 2018 con 51 pacientes con el diagnóstico de ausencia bilateral congénita de conductos deferentes. Se analizaron la presencia de mutaciones del gen CFTR y 5T, fibrosis quística y tasas de embarazo y nacimientos. RESULTADOS: 80,4% tenían alguna mutación del CFTR siendo la DeltaF508 la más frecuente (51%). El genotipo descrito con mayor frecuencia era 7T/9T (31,4%) con la presencia de polimorfismo 5T en hasta el 25,5% de los casos. Las tasas de nacimientos globales fueron del 34% en el grupo que utilizaba espermatozoides del marido. Cuando se compara la presencia de 5T, observamos una disminución en las tasas de nacimientos en los portadores de esta mutación, sin obtener significación estadística (Tasa de nacimientos 5T/no-5T: 7,1/28%, p = 0,45). No se encontraron diferencias en la comparativa entre la presencia de FQ severa, mutaciones comunes del gen CFTR y los parámetros relacionados con la ICSI. CONCLUSIONES: El análisis de la presencia de polimorfismo 5T en los pacientes con ausencia bilateral congénita de conductos deferentes puede añadir información para la predicción de los resultados de las técnicas de reproducción asistida

Implementation of massive sequencing in the genetic diagnosis of hereditary cancer syndromes: diagnostic performance in the Hereditary Cancer Programme of the Valencia Community (FamCan-NGS).

BACKGROUND: Approximately 5 to 10% of all cancers are caused by inherited germline mutations, many of which are associated with different Hereditary Cancer Syndromes (HCS). In the context of the Program of Hereditary Cancer of the Valencia Community, individuals belonging to specific HCS and their families receive genetic counselling and genetic testing according to internationally established guidelines. The current diagnostic approach is based on sequencing a few high-risk genes related to each HCS; however, this method is time-consuming, expensive and does not achieve a confirmatory genetic diagnosis in many cases. This study aims to test the level of improvement offered by a Next Generation Sequencing (NGS) gene-panel compared to the standard approach in a diagnostic reference laboratory setting. METHODS: A multi-gene NGS panel was used to test a total of 91 probands, previously classified as non-informative by analysing the high-risk genes defined in our guidelines. RESULTS: Nineteen deleterious mutations were detected in 16% of patients, some mutations were found in already-tested high-risk genes (BRCA1, BRCA2, MSH2) and others in non-prevalent genes (RAD51D, PALB2, ATM, TP53, MUTYH, BRIP1). CONCLUSIONS: Overall, our findings reclassify several index cases into different HCS, and change the mutational status of 14 cases from non-informative to gene mutation carriers. In conclusion, we highlight the necessity of incorporating validated multi-gene NGS panels into the HCSs diagnostic routine to increase the performance of genetic diagnosis.

Chimeric Genes in Deletions and Duplications Associated with Intellectual Disability.

We report on three nonrelated patients with intellectual disability and CNVs that give rise to three new chimeric genes. All the genes forming these fusion transcripts may have an important role in central nervous system development and/or in gene expression regulation, and therefore not only their deletion or duplication but also the resulting chimeric gene may contribute to the phenotype of the patients. Deletions and duplications are usually pathogenic when affecting dose-sensitive genes. Alternatively, a chimeric gene may also be pathogenic by different gain-of-function mechanisms that are not restricted to dose-sensitive genes: the emergence of a new polypeptide that combines functional domains from two different genes, the deregulated expression of any coding sequence by the promoter region of a neighboring gene, and/or a putative dominant-negative effect due to the preservation of functional domains of partially truncated proteins. Fusion oncogenes are well known, but in other pathologies, the search for chimeric genes is disregarded. According to our findings, we hypothesize that the frequency of fusion transcripts may be much higher than suspected, and it should be taken into account in the array-CGH analyses of patients with intellectual disability.

High diagnostic yield of syndromic intellectual disability by targeted next-generation sequencing.

BACKGROUND: Intellectual disability is a very complex condition where more than 600 genes have been reported. Due to this extraordinary heterogeneity, a large proportion of patients remain without a specific diagnosis and genetic counselling. The need for new methodological strategies in order to detect a greater number of mutations in multiple genes is therefore crucial. METHODS: In this work, we screened a large panel of 1256 genes (646 pathogenic, 610 candidate) by next-generation sequencing to determine the molecular aetiology of syndromic intellectual disability. A total of 92 patients, negative for previous genetic analyses, were studied together with their parents. Clinically relevant variants were validated by conventional sequencing. RESULTS: A definitive diagnosis was achieved in 29 families by testing the 646 known pathogenic genes. Mutations were found in 25 different genes, where only the genes KMT2D, KMT2A and MED13L were found mutated in more than one patient. A preponderance of de novo mutations was noted even among the X linked conditions. Additionally, seven de novo probably pathogenic mutations were found in the candidate genes AGO1, JARID2, SIN3B, FBXO11, MAP3K7, HDAC2 and SMARCC2. Altogether, this means a diagnostic yield of 39% of the cases (95% CI 30% to 49%). CONCLUSIONS: The developed panel proved to be efficient and suitable for the genetic diagnosis of syndromic intellectual disability in a clinical setting. Next-generation sequencing has the potential for high-throughput identification of genetic variations, although the challenges of an adequate clinical interpretation of these variants and the knowledge on further unknown genes causing intellectual disability remain to be solved.

Negative impact on clinical outcome of the mutational co-occurrence of SF3B1 and DNMT3A in refractory anemia with ring sideroblasts (RARS).

The incidence of SF3B1 mutations in patients with RARS is high. Recently, it has been shown that SF3B1 and DNMT3A mutations overlap more often than expected, although it is not clear how this could affect the disease. We studied SF3B1 and DNMT3A in 123 RARS patients: 101 out of 123 samples (82%) had somatic mutations in SF3B1, and 13 of them (13%) showed a co-mutation (SF3B1mutDNMT3Amut). All co-mutated patients had a normal karyotype, and 12 of them (92%) were lower-risk patients (IPSS and IPSS-R). Despite their favorable profile, SF3B1mutDNMT3Amut patients showed a higher RBC transfusion dependency (92% versus 48%, p = .007), a shorter overall survival (OS) (median, 30 versus 97 months, p = .034), and a higher risk of progression to acute myeloid leukemia (AML) at 5 years (25% versus 2%, p = .023) than SF3B1mutDNMT3Awt patients. In conclusion, DNMT3A mutations are present in a significant proportion of SF3B1mut patients with a negative clinical impact.

De novo mutations in genes of mediator complex causing syndromic intellectual disability: mediatorpathy or transcriptomopathy?

BACKGROUND: Mutations in the X-linked gene MED12 cause at least three different, but closely related, entities of syndromic intellectual disability. Recently, a new syndrome caused by MED13L deleterious variants has been described, which shows similar clinical manifestations including intellectual disability, hypotonia, and other congenital anomalies. METHODS: Genotyping of 1,256 genes related with neurodevelopment was performed by next-generation sequencing in three unrelated patients and their healthy parents. Clinically relevant findings were confirmed by conventional sequencing. RESULTS: Each patient showed one de novo variant not previously reported in the literature or databases. Two different missense variants were found in the MED12 or MED13L genes and one nonsense mutation was found in the MED13L gene. CONCLUSION: The phenotypic consequences of these mutations are closely related and/or have been previously reported in one or other gene. Additionally, MED12 and MED13L code for two closely related partners of the mediator kinase module. Consequently, we propose the concept of a common MED12/MED13L clinical spectrum, encompassing Opitz-Kaveggia syndrome, Lujan-Fryns syndrome, Ohdo syndrome, MED13L haploinsufficiency syndrome, and others.

TH and DCX mRNAs in peripheral blood and bone marrow predict outcome in metastatic neuroblastoma patients.

PURPOSE: In metastatic neuroblastoma (NB) patients, accurate risk stratification and disease monitoring would reduce relapse probabilities. This study aims to evaluate the independent prognostic significance of detecting tyrosine hydroxylase (TH) and doublecortin (DCX) mRNAs by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) in peripheral blood (PB) and bone marrow (BM) samples from metastatic NB patients. PROCEDURES: RT-qPCR was performed on PB and BM samples from metastatic NB patients at diagnosis, post-induction therapy and at the end of treatment for TH and DCX mRNAs detection. RESULTS: High levels of TH and DCX mRNAs when detected in PB and BM at diagnosis independently predicted worse outcome in a cohort of 162 metastatic NB. In the subgroup of high-risk metastatic NB, TH mRNA detected in PB remained as independent predictor of EFS and OS at diagnosis. After the induction therapy, high levels of TH mRNA in PB and DCX mRNA in BM independently predicted poor EFS and OS. Furthermore TH mRNA when detected in BM predicted worse EFS. TH mRNA in PB samples at the end of treatment is an independent predictor of worse outcome. CONCLUSION: TH and DCX mRNAs levels in PB and BM assessed by RT-qPCR should be considered in new pre-treatment risk stratification strategies to reliable estimate outcome differences in metastatic NB patients. In those high-risk metastatic NB, TH and DCX mRNA quantification could be used for the assessment of response to treatment and for early detection of progressive disease or relapses.

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.

Novel mutations of NFIX gene causing Marshall-Smith syndrome or Sotos-like syndrome: one gene, two phenotypes.

BACKGROUND: Only 15 point mutations in NFIX gene have been reported so far, nine of them cause the Marshall-Smith syndrome (MSS) and the remaining mutations lead to an overgrowth disorder with a less severe phenotype, defined as Sotos-like. METHODS: The clinical findings in three patients with MSS and two patients with a Sotos-like phenotype are presented. Analysis of the NFIX gene was performed both by conventional or next-generation sequencing. RESULTS: Five de novo mutations in NFIX gene were identified, four of them not previously reported. Two frameshift mutations and a donor-splice one caused MSS, while two missense mutations in the DNA binding/dimerisation domain entailed an overgrowth syndrome with some clinical features resembling Sotos syndrome, accompanied by a marfanoid habitus, very low BMI, long narrow face, or arachnodactyly. CONCLUSION: Marshall-Smith mutations are scattered through exons 6-10 of NFIX gene, while most point mutations causing an overgrowth syndrome are clustered in exon 2. Clinical features of this overgrowth syndrome may well be considered an intermediate phenotype between Sotos and Marfan syndromes.

In Pursuit of New Imprinting Syndromes by Epimutation Screening in Idiopathic Neurodevelopmental Disorder Patients.

Alterations of epigenetic mechanisms, and more specifically imprinting modifications, could be responsible of neurodevelopmental disorders such as intellectual disability (ID) or autism together with other associated clinical features in many cases. Currently only eight imprinting syndromes are defined in spite of the fact that more than 200 genes are known or predicted to be imprinted. Recent publications point out that some epimutations which cause imprinting disorders may affect simultaneously different imprinted loci, suggesting that DNA-methylation may have been altered more globally. Therefore, we hypothesised that the detection of altered methylation patterns in known imprinting loci will indirectly allow identifying new syndromes due to epimutations among patients with unexplained ID. In a screening for imprinting alterations in 412 patients with syndromic ID/autism we found five patients with altered methylation in the four genes studied: MEG3, H19, KCNQ1OT1, and SNRPN. Remarkably, the cases with partial loss of methylation in KCNQ1OT1 and SNRPN present clinical features different to those associated with the corresponding imprinting syndromes, suggesting a multilocus methylation defect in accordance with our initial hypothesis. Consequently, our results are a proof of concept that the identification of epimutations in known loci in patients with clinical features different from those associated with known syndromes will eventually lead to the definition of new imprinting disorders.

Malformación de Arnold-Chiari en el síndrome de Noonan y otros síndromes de la vía RAS/MAPK / Arnold-Chiari malformation in Noonan syndrome and other syndromes of the RAS/MAPK pathway

Introducción. El síndrome de Noonan (SN) y otros síndromes con fenotipo similar, como LEOPARD, cardiofaciocutáneo, Costello y Legius, están asociados a mutaciones en genes incluidos en la vía RAS/MAPK (rasopatías), una importante vía de señalización relacionada con la proliferación celular. El descenso de las amígdalas cerebelares dentro del canal medular cervical, conocido como malformación de Arnold-Chiari (MAC), se ha descrito en pacientes afectos de SN, lo que ha llevado a sugerir que la MAC podría formar parte del espectro fenotípico del SN. Presentamos dos casos con SN y MAC. Casos clínicos. Caso 1: mujer de 29 años con fenotipo de Noonan. Fue intervenida a los 9 años de estenosis valvular pulmonar. A los 27 años, presentó MAC sintomática que precisó descompresión quirúrgica. Presentaba mutación c.922A>G (N308D) en el gen PTPN perteneciente a la vía RAS/MAPK. Caso 2: niña de 10 años con fenotipo de Noonan y MAC asintomática detectada en resonancia magnética cerebral. Era portadora de la mutación c.923A>G (N308S) en el gen PTPN11. Conclusiones. Hemos encontrado en la bibliografía seis pacientes con esta asociación, cuatro con fenotipo Noonan y dos con LEOPARD. Nuestros dos pacientes aportan evidencia suplementaria a la hipótesis de que la MAC formaría parte del espectro fenotípico del SN. El escaso número de pacientes publicados con esta asociación no permite extraer recomendaciones sobre el momento y la frecuencia de estudio de neuroimagen; no obstante, una exploración neurológica cuidadosa debería incluirse en la guía anticipatoria de salud en los síndromes de la vía RAS/MAPK (AU)

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-yearold 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 (AU)