Twin infant with lymphatic dysplasia diagnosed with Noonan syndrome by molecular genetic testing

Severe generalized edema in a premature neonate: A case report and literature review

Key Clinical Message

With no family history, and an atypical phenotype, the clinical diagnosing of Noonan syndrome (NS) can be very difficult. The present case emphasized that generalized edema in neonates may be the potential first symptom of NS.

Abstract

Severe generalized edema is a rare pathological condition with high mortality in newborns, in particular the premature infants. It is characterized by the extensive subcutaneous tissue edema and the accumulation of fluid in neonatal body fluid compartments. The etiology and pathogenesis of hydrops in neonates are quite complex. Generally speaking, hydrops can be divided into immune hydrops and non-immune hydrops according to the etiology. It is still challenging in treating severe neonatal edema. In this study, we presented a preterm newborn with severe generalized edema after birth, which was finally diagnosed with Noonan syndrome (NS). The infant clinically manifested as severe generalized edema alone, without the involvement of multiple organ malformation. Generalized edema in neonates was probably the first symptom of NS. Therefore, differential diagnosis of NS is necessary for infants developing generalized edema.

Case report: Noonan syndrome with protein-losing enteropathy

Background: Noonan syndrome (NS) is characterized by typical facial features, short stature, congenital heart defects and other comorbidities. Lymphedema and chylous pleural effusions are also common in NS, but protein-losing enteropathy (PLE) is rarely reported. Case presentation: We present the case of a 19-year-old Chinese woman presenting with PLE. Small intestine biopsy showed obvious expansion of lymphatic vessels. The gene mutation results of the patient indicated a c.184T>G missense mutation (p.Tyr62Asp) in the PTPN11 gene (NM_002834.3). Conclusion: NS accompanied by PLE is not common, but hypoproteinemia attributable to PLE may be more common in patients with NS than previously thought. It remains uncertain whether mutation of the PTPN11 gene is related to PLE, indicating that further research is needed.

PTPN11 c.853T>C (p.Phe285Leu) mutation in Noonan syndrome with chylothorax

Recent advances in molecular and genetic approaches have identified a number of genes responsible for Noonan syndrome (NS). However, there has been limited analysis of the genotype-phenotype correlation of NS patients. Here, we report the case of a Japanese patient with NS possessing a c.853T>C (p.Phe285Leu) mutation in the gene encoding protein-tyrosine phosphatase, nonreceptor-type 11 (PTPN11). To clarify genotype-phenotype correlations, the accumulation of data on the clinical course of patients with genetically confirmed NS is important. We summarized the cases with mutations at PTPN11 position 285 and found that c854T>C (p.Phe285Ser) is the most common mutation at this position. In these reports, although little is mentioned about the genotype-phenotype correlation, two patients with NS possessing the PTPN11 c854T>C (p.Phe285Ser) mutation accompanied by chylothorax are described. There is still a lack of detailed information about the phenotype associated with the c.853T>C (p.Phe285Leu) mutation observed in this case. More research is needed to better understand these cases.

Trametinib for Refractory Chylous Effusions and Systemic Complications in Children with Noonan Syndrome

OBJECTIVE

To evaluate the effect of the RAS-MAPK pathway inhibitor trametinib on medically refractory chylous effusions in 3 hospitalized patients with Noonan syndrome.

STUDY DESIGN

Pharmacologic MEK1/2 inhibition has been used to treat conditions associated with Noonan syndrome, given that activation of RAS-MAPK pathway variants leads to downstream MEK activation. We describe our experience with 3 patients with Noonan syndrome (owing to variants in 3 distinct genes) and refractory chylous effusions treated successfully with MEK inhibition. A monitoring protocol was established to standardize medication dosing and monitoring of outcome measures.

RESULTS

Subjects demonstrated improvement in lymphatic leak with additional findings of improved growth and normalization of cardiac and hematologic measurements. Trametinib was administered safely, with only moderate skin irritation in 1 subject.

CONCLUSIONS

Improvements in a variety of quantifiable measurements highlight the potential utility of MEK1/2 inhibition in patients with Noonan syndrome and life-threatening lymphatic disease. Larger, prospective studies are needed to confirm efficacy and assess long-term safety.

Lymphatic Abnormalities in Noonan Syndrome Spectrum Disorders: A Systematic Review

Noonan syndrome spectrum disorders are a group of phenotypically related conditions, resembling Noonan syndrome, caused by germline pathogenic variants in genes within the Ras/mitogen-activated protein kinase (Ras/MAPK) signalling pathway. Lymphatic dysplasia with a clinical lymphatic abnormality is one of the major features. We performed a systematic review to get more insight in (1) the prevalence of clinically lymphatic abnormalities in patients with a genetically proven Noonan syndrome spectrum disorder, (2) if a genotype-lymphatic phenotype relation can be found and describe the clinical presentation and course of the lymphatic abnormality. Most studies report patients with Noonan syndrome. Prenatally, the prevalence of increased nuchal translucency differs from 7% in patients with pathogenic PTPN11 variants to 38% in patients with pathogenic RIT1 variants, and the prevalence of pleural effusions differed from 7% in patients with pathogenic SOS1 to 29% in patients with pathogenic RIT1 variants. Postnatally, the prevalence of lymphedema differs from 16% in patients with pathogenic PTPN11 variants to 44% in patients with pathogenic SOS1 variants, and the prevalence of acquired chylothorax is 4% in patients with pathogenic RIT1 variants. Lymphatic abnormalities do occur in patients with cardiofaciocutaneous syndrome and Costello syndrome. In conclusion, Noonan syndrome spectrum disorders, Noonan syndrome in particular, are associated with lymphatic abnormalities. Combining the available published literature about genetically proven Noonan syndrome spectrum disorders, it appears likely that the lifetime prevalence of these abnormalities in Noonan syndrome is higher than the 20% that were generally accepted so far. This is increasingly important, because the activation of the RAS/MAPK pathway can be inhibited by RAS/MAPK inhibitors, and clinically severe lymphatic abnormalities may improve.

A PTPN11 mutation in a woman with Noonan syndrome and protein-losing enteropathy

Background

Noonan syndrome is an autosomal dominant, variably expressed multisystem disorder characterized by specific facial and cardiac defects, delayed growth, ectodermal abnormalities, and lymphatic dysplasias. Lymphedema and chylous pleural effusions are common in Noonan syndrome, but protein-losing enteropathy (PLE) has only rarely been described in the condition and little is known about its genetic associations.

Case presentation

We report the case of a 30-year-old Chinese woman who developed severe recurrent edema and hypoproteinemia. Gastroduodenoscopy showed a “snowflake” appearance of lymphangiectasia in the duodenum, and CT reconstruction of the small intestine showed segmental thickening of the intestinal wall with localized stenosis. Whole exome sequencing revealed that the patient harbored a pathogenic variant of PTPN11 (c.A922G p.N308D), which was unfortunately inherited by her 2.5-year-old daughter who had short stature and atrial septal defect but no hypoproteinemia.

Conclusions

This case of Noonan syndrome with PLE was associated with a PTPN11 mutation. A comprehensive review of PLE in Noonan syndrome revealed that PLE often presents late in this context but there is no clear genotype-phenotype correlation. Genetic evaluation with next-generation sequencing can be useful for securing the diagnosis and planning early intervention and management.

Cardiac transplantation in children with Noonan syndrome

NS and related RAS/MAPK pathway (RASopathy) disorders are the leading genetic cause of HCM presenting in infancy. HCM is a major cause of morbidity and mortality in children with Noonan spectrum disorders, especially in the first year of life. Previously, there have been only isolated reports of heart transplantation as a treatment for heart failure in NS. We report on 18 patients with NS disorders who underwent heart transplantation at seven US pediatric heart transplant centers. All patients carried a NS diagnosis: 15 were diagnosed with NS and three with NSML. Sixteen of eighteen patients had comprehensive molecular genetic testing for RAS pathway mutations, with 15 having confirmed pathogenic mutations in PTPN11, RAF1, and RIT1 genes. Medical aspects of transplantation are reported as well as NS-specific medical issues. Twelve of eighteen patients described in this series were surviving at the time of data collection. Three patients died following transplantation prior to discharge from the hospital, and another three died post-discharge. Heart transplantation in NS may be a more frequent occurrence than is evident from the literature or registry data. A mortality rate of 33% is consistent with previous reports of patients with HCM transplanted in infancy and early childhood. Specific considerations may be important in evaluation of this population for heart transplant, including a potentially increased risk for malignancies as well as lymphatic, bleeding, and coagulopathy complications.

Prevalence of Noonan spectrum disorders in a pediatric population with valvar pulmonary stenosis

OBJECTIVE

To evaluate the prevalence of Noonan spectrum disorders (NSD) in a pediatric population with valvar pulmonary stenosis (vPS) and identify the clinical characteristics that differentiate those with NSD from those without NSD.

DESIGN

A retrospective chart review of 204 patients diagnosed with vPS between 9/1/2012 and 12/1/2016 at a pediatric medical center was performed. The quantitative features of vPS, genetic diagnosis information, and phenotypic characteristics of Noonan syndrome were collected. Chi-square test, Fisher's exact test, t test, Wilcoxon rank-sum test, and ANOVA were used for comparisons among the groups. Logistic regression was used to test for the association between the clinical characteristics and the presence of NSD.

RESULTS

Syndromic diagnoses were made in 10% of the children with vPS, with NSD accounting for 6%. Hypertrophic cardiomyopathy (P < .0001), short stature (P < .0001), developmental delay (P < .0001), ophthalmological abnormalities (P < .0001), pectus carinatum/excavatum (P = .01), neurological abnormalities (P = .022), and aortic stenosis (P = .031) were present more often in individuals with NSD compared to nonsyndromic vPS. A logistic regression analysis showed a 4.8-fold increase in odds for NSD for each additional characteristic (P < .0001).

CONCLUSIONS

At least 6% of the children with vPS have an underlying NSD. Individuals with vPS and NSD were significantly more likely to have additional features known to be associated with NSD than those with vPS without NSD. We conclude that vPS in the presence of one or more significant characteristics should prompt referral for genetic evaluation as a guide to ascertain patients at risk for NSD while optimizing the use of clinical genetics evaluation and potential genetic testing.

Noonan syndrome: Severe phenotype and PTPN11 mutations

INTRODUCTION AND OBJECTIVE

Noonan syndrome (NS) is a genetic disorder characterized by a wide range of distinctive features and health problems. It caused in 50% of cases by missense mutations in PTPN11 gene. It has been postulated that it is possible to predict the disease course based into the impact of mutations on the protein.

PATIENTS AND METHODS

We report two cases of severe NS phenotype including hydrops fetalis. PTPN11 gene was studied in germinal cells of both patients by sequencing.

RESULTS

Two different mutations (p.Gly503Arg and p.Met504Val) was detected in PTPN11 gene.

DISCUSSION

These mutations have been reported previously, and when they were germinal variants, patients presented classic NS, NS with other malignancies and recently, p.Gly503Arg has been also observed in a patient with severe NS and hydrops fetalis, as our cases. Therefore, these observations shade light on that it is not always possibly to determine the genotype-phenotype relation based into the impact of mutations on the protein in NS patients with PTPN11 mutations.

Mutational landscape, clonal evolution patterns, and role of RAS mutations in relapsed acute lymphoblastic leukemia

Although multiagent combination chemotherapy is curative in a significant fraction of childhood acute lymphoblastic leukemia (ALL) patients, 20% of cases relapse and most die because of chemorefractory disease. Here we used whole-exome and whole-genome sequencing to analyze the mutational landscape at relapse in pediatric ALL cases. These analyses identified numerous relapse-associated mutated genes intertwined in chemotherapy resistance-related protein complexes. In this context, RAS-MAPK pathway-activating mutations in the neuroblastoma RAS viral oncogene homolog (NRAS), kirsten rat sarcoma viral oncogene homolog (KRAS), and protein tyrosine phosphatase, nonreceptor type 11 (PTPN11) genes were present in 24 of 55 (44%) cases in our series. Interestingly, some leukemias showed retention or emergence of RAS mutant clones at relapse, whereas in others RAS mutant clones present at diagnosis were replaced by RAS wild-type populations, supporting a role for both positive and negative selection evolutionary pressures in clonal evolution of RAS-mutant leukemia. Consistently, functional dissection of mouse and human wild-type and mutant RAS isogenic leukemia cells demonstrated induction of methotrexate resistance but also improved the response to vincristine in mutant RAS-expressing lymphoblasts. These results highlight the central role of chemotherapy-driven selection as a central mechanism of leukemia clonal evolution in relapsed ALL, and demonstrate a previously unrecognized dual role of RAS mutations as drivers of both sensitivity and resistance to chemotherapy.

Recognizable syndromes in the newborn period

Making the diagnosis of genetic syndromes in the neonatal period can be challenging, as limited information concerning growth and development is available. The pattern of dysmorphic features and malformations is, therefore, correspondingly more important in syndrome recognition. The authors provide specific examples of the differences in the presentation for selected syndromes between the newborn period and later childhood. The purpose is to describe the variation in presentation that can occur with chronologic age and to aid in the early diagnosis of these conditions.