Allelic dropout in PAH affecting the results of genetic diagnosis in phenylketonuria

Objectives Phenylketonuria (PKU) is an inherited autosomal recessive disorder of phenylalanine metabolism. It is mainly caused by a deficiency in phenylalanine hydroxylase (PAH) and frequently diagnosed with Sanger sequencing. To some extent, allelic dropout can explain the inconsistency in genotype and phenotype. Methods Three families were evaluated through DNA sequence analysis, multiplex ligation-dependent probe amplification (MLPA) and prenatal diagnosis technologies. The possibility of inconsistency in phenotype and genotype with c.331C>T variant was analysed. Results Through pedigree analysis, three mothers carried a homozygous c.331C>T variant, which was a false-positive result. New primers were used, and this error was caused by allelic dropout. In this case, c.158G>A was likely a benign variant. Conclusions Sequence variants in primer-binding regions could cause allelic dropout, creating unpredictable errors in genotyping. Our results emphasised the need for careful measures to treat genotype–phenotype inconsistencies.

Steroid hormone profiles and molecular diagnostic tools in pediatric patients with non-CAH primary adrenal insufficiency

Background There is a significant challenge of attributing specific diagnoses to patients with primary adrenal insufficiency of unknown etiology other than congenital adrenal hyperplasia (non-CAH PAI). Specific diagnoses per se may guide personalized treatment or may illuminate pathophysiology. Objective Investigation of the efficacy of steroid hormone profiles and high-throughput sequencing methods in establishing the etiology in non-CAH PAI of unknown origin. Design Paediatric patients with non-CAH PAI whose etiology could not be established by clinical and biochemical characteristics were enrolled. Genetic analysis was performed using targetedgene panel sequencing (TPS) and whole-exome sequencing (WES). Plasma adrenal steroids were quantified by liquid chromatography-mass spectrometry and compared to that of controls. Setting Eighteen pediatric endocrinology clinics. Patients Forty-one patients (17 females, median age: 3 months, range: 0-8 years) with non-CAH PAI of unknown etiology. Results A genetic diagnosis was obtained in 29 (70.7%) patients by TPS. Further molecular diagnosis could not be achieved by WES. Compared to healthy control group, patients showed lower steroid concentrations, most significantly in cortisone, cortisol, and corticosterone (p<0.0001, area under the ROC curve: 0.96, 0.88, 0.87, respectively). Plasma cortisol<4 ng/mL, cortisone<11 ng/mL, and corticosterone<0.11 ng/mL had >95% specificity to ensure the diagnosis of non-CAH PAI of unknown etiology. Conclusion Steroid hormone profiles are highly sensitive for the diagnosis of non-CAH PAI of unknown etiology, while they are unlikely to point out a specific molecular diagnosis. TPS is an optimal approach in the molecular diagnosis of these patients with high efficacy, while little additional benefit is expected from WES.

Clinical and genetic diagnosis of thirteen Japanese patients with hereditary spherocytosis

Hereditary spherocytosis is the most frequent cause of hereditary hemolytic anemia and is classified into five subtypes (SPH1-5) according to OMIM. Because the clinical and laboratory features of patients with SPH1-5 are variable, it is difficult to classify these patients into the five subtypes based only on these features. We performed target capture sequencing in 51 patients with hemolytic anemia associated with/without morphological abnormalities in red blood cells. Thirteen variants were identified in five hereditary spherocytosis-related genes (six in ANK1 [SPH1]; four in SPTB [SPH2]; and one in each of SPTA1 [SPH3], SLC4A1 [SPH4], and EPB42 [SPH5]). Among these variants, seven were novel. The distribution pattern of the variants was different from that reported previously in Japan but similar to those reported in other Asian countries. Comprehensive genomic analysis would be useful and recommended, especially for patients without a detailed family history and those receiving frequent blood transfusions due to chronic hemolytic anemia.

The Application of Whole−Exome Sequencing in Patients With FUO

BackgroundFever of unknown origin (FUO) is still a challenge for clinicians. Next-generation sequencing technologies, such as whole exome sequencing (WES), can be used to identify genetic defects in patients and assist in diagnosis. In this study, we investigated the application of WES in individuals with FUO.MethodsWe performed whole-exome sequencing on 15 FUO patients. Clinical information was extracted from the hospital information system.ResultsIn 7/15 samples, we found positive results, including potentially causative mutations across eight different genes: CFTR, CD209, IRF2BP2, ADGRV 1, TYK2, MEFV, THBD and GATA2.ConclusionsOur results show that whole-exome sequencing can promote the genetic diagnosis and treatment of patients with FUO.

Proactive Variant Effect Mapping to Accelerate Genetic Diagnosis for Pediatric Cardiac Arrest

While genetic testing is becoming standard of care for patients with potentially inherited cardiovascular disease, the prevalence of uncertain results severely limits its utility. One promising approach is to generate variant effect maps that report the function of all possible variants in a gene prospectively. The proactive clinical application of these maps is nascent, and requires careful integration with current American College of Medical Genetics guidelines for variant interpretation. Here, we describe three pediatric cases of cardiac arrest or sudden cardiac death with variants of uncertain significance in calmodulin genes. We demonstrate the prospective clinical utility of a calmodulin variant effect map to inform variant interpretation, and therefore diagnosis and family care, in each case. This study was approved by the Stanford University and Vanderbilt University Medical Center IRBs. Consent was waived based on low risk of de-identified retrospective data collection per the IRB.

A genomic autopsy identifies causes of perinatal death and provides options to prevent recurrence

Perinatal death, of a fetus or newborn, is a devastating event for families. Following nationwide multicentre recruitment, we assessed ‘genomic autopsy’ as an adjunct to standard autopsy for 200 families who experienced perinatal death, and provided a definite or candidate genetic diagnosis in 105 families. From this understudied cohort, half of the (candidate) diagnoses were phenotype expansions or novel disease genes, revealing previously unknown in-utero presentations of existing developmental disorders, and genomic disorders that are likely incompatible with life. Among the definite diagnoses, 43% were recessively or dominantly inherited, posing a 25% or 50% recurrence risk for future pregnancies. Ten families used their diagnosis for preimplantation or prenatal diagnosis of 12 pregnancies, facilitating the delivery of ten healthy newborns and management of two affected pregnancies. We emphasize the clinical importance of genomic investigations of perinatal death, with short turn-around times, enabling accurate counselling and options for families to prevent recurrence.

MEN1 Surveillance Guidelines: Time to (re)Think?

Clinical Practice Guidelines for patients with Multiple Endocrine Neoplasia type 1 (MEN1) recommend a variety of surveillance options. Given progress over the past decade in this area, it is timely to evaluate their ongoing utility. MEN1 is characterized by the development of synchronous or asynchronous tumors affecting a multitude of endocrine and non-endocrine tissues, resulting in premature morbidity and mortality, such that the rationale for undertaking surveillance screening in at-risk individuals appears robust. Current guidelines recommend an intensive regimen of clinical, biochemical and radiological surveillance commencing in early childhood for those with a clinical or genetic diagnosis of MEN1, with the aim of early tumor detection and treatment. Although it is tempting to assume that such screening results in patient benefits and improved outcomes, the lack of a strong evidence base for several aspects of MEN1 care, and the potential for iatrogenic harms related to screening tests or interventions of unproven benefit, make such assumptions potentially unsound. Furthermore, the psychological, as well as economic burdens of intensive screening remain largely unstudied. Although screening undoubtedly constitutes an important component of MEN1 patient care, this perspective aims to highlight some of the current uncertainties and challenges related to existing MEN1 guidelines with a particular focus on the role of screening for pre-symptomatic tumors. Looking forward, a screening approach that acknowledges these limitations and uncertainties and places the patient at the heart of the decision-making process, is advocated.

Comprehensive Genetic Analysis of RASopathy in the Era of Next-Generation Sequencing and Definition of a Novel Likely Pathogenic KRAS Variation

<b><i>Introduction:</i></b> Germline pathogenic variations of the genes encoding the components of the Ras-MAPK pathway are found to be responsible for RASopathies, a clinically and genetically heterogeneous group of diseases. In this study, we aimed to present the results of patients genetically investigated for RASopathy-related mutations in our Genetic Diagnosis Center. <b><i>Methods:</i></b> The results of 51 unrelated probands with RASopathy and 4 affected relatives (31 male, 24 female; mean age: 9.327 ± 8.214) were included in this study. Mutation screening was performed on DNA samples from peripheral blood of the patients either by Sanger sequencing of <i>PTPN11</i> hotspot regions (10/51 probands), or by a targeted amplicon next-generation sequencing panel (41/51 probands) covering the exonic regions of <i>BRAF</i>, <i>CBL</i>, <i>HRAS</i>, <i>KRAS</i>, <i>LZTR1</i>, <i>MAP2K1</i>, <i>MAP2K2</i>, <i>NF1</i>, <i>NRAS</i>, <i>PTPN11</i>, <i>RAF1</i>, <i>RASA2</i>, <i>RIT1</i>, <i>SHOC2</i>, <i>SOS1</i>, <i>SOS2</i>, <i>SPRED1</i>, and <i>KAT6B</i> genes. <b><i>Results:</i></b> Pathogenic/likely pathogenic variations found in 22 out of 51 probands (43.13%) and their 4 affected family members were located in <i>PTPN11</i>, <i>BRAF</i>, <i>KRAS</i>, <i>NF1</i>, <i>RAF1</i>, <i>SOS1</i>, and <i>SHOC2</i> genes. The c.148A&#x3e;C (p.Thr50Pro) variation in the <i>KRAS</i> gene was a novel variant detected in a sibling in our patient cohort. We found supportive evidence for the pathogenicity of the <i>NF1</i> gene c.5606G&#x3e;T (p.Gly1869Val) variation which we defined in an affected boy who inherited the mutation from his affected father. <b><i>Conclusion:</i></b> Although <i>PTPN11</i> is the most frequently mutated gene in our patient cohort, as in most previous reports, different mutation distribution among the other genes studied motivates the use of a next-generation sequencing gene panel including the possible responsible genes.

Clinical Genetics of Inherited Arrhythmogenic Disease in the Pediatric Population

Sudden death is a rare event in the pediatric population but with a social shock due to its presentation as the first symptom in previously healthy children. Comprehensive autopsy in pediatric cases identify an inconclusive cause in 40–50% of cases. In such cases, a diagnosis of sudden arrhythmic death syndrome is suggested as the main potential cause of death. Molecular autopsy identifies nearly 30% of cases under 16 years of age carrying a pathogenic/potentially pathogenic alteration in genes associated with any inherited arrhythmogenic disease. In the last few years, despite the increasing rate of post-mortem genetic diagnosis, many families still remain without a conclusive genetic cause of the unexpected death. Current challenges in genetic diagnosis are the establishment of a correct genotype–phenotype association between genes and inherited arrhythmogenic disease, as well as the classification of variants of uncertain significance. In this review, we provide an update on the state of the art in the genetic diagnosis of inherited arrhythmogenic disease in the pediatric population. We focus on emerging publications on gene curation for genotype–phenotype associations, cases of genetic overlap and advances in the classification of variants of uncertain significance. Our goal is to facilitate the translation of genetic diagnosis to the clinical area, helping risk stratification, treatment and the genetic counselling of families.