The utility of exome sequencing for fetal pleural effusions

RASopathies are the most common set of monogenic syndromes identified by exome sequencing for nonimmune hydrops fetalis: A systematic review and meta-analysis

RASopathies are a group of malformation syndromes known to lead to nonimmune hydrops fetalis (NIHF) in severe presentations. Pathogenic variants can be de novo or parentally inherited. Despite being a known frequent presentation, the fraction of monogenic NIHF cases due to RASopathies is limited in the literature. Also, the specific parental contribution of RASopathies to NIHF is not well described. Our objective was to review pooled exome sequencing (ES) diagnostic yield of RASopathies for NIHF and to determine the parental contribution of RASopathy to NIHF. We performed a systematic review of prenatal ES studies from January 1, 2000 to August 1, 2022. Thirty-six studies met inclusion criteria. Cases with RASopathy gene variants were reviewed. NIHF cases were further classified as isolated or non-isolated. Thirty-six ES studies including 46 pregnancies with NIHF and a diagnosed RASopathy were reviewed. Forty-four diagnostic variants and 2 variants of uncertain significance in 12 RASopathy genes were identified. Expanding on what was previously published, a total of 506 NIHF cases were extracted with 191 cases yielding a positive diagnosis by ES. The overall rate of RASopathy diagnosis in clinically diagnosed NIHF cases was 9% (44/506). The rate of RASopathy diagnosis among NIHF cases with positive genetic diagnosis by ES was 23% (44/191). Of the 46 cases identified, 13 (28%) variants were parentally inherited; specifically, 5/13 (38%) maternal, 3/13 (23%) paternal, 2/13 (15%) biparental, and 3/13 (23%) unspecified. Majority of NIHF cases 29/46 (63%) were isolated. Among NIHF cases with positive ES diagnoses, RASopathy diagnostic yield by ES was 23%. NIHF secondary to RASopathies was parentally inherited in 28% of cases. Most cases of NIHF due to RASopathy were isolated, with no prenatal detection of associated anomalies.

Syndromic and single gene disorders associated with fetal pleural effusion (I): Noonan syndrome, RASopathy and congenital lymphatic anomalies

Fetal pleural effusion has been reported to be associated with chromosomal abnormalities, genetic syndromes, obstructive uropathy, lymphatic vessel abnormalities such as Noonan syndrome, RASopathy and congenital lymphatic anomalies, thoracic cavity defects, Rh or ABO incompatibility, non-immune hydrops fetalis, infections, congenital cardiac anomalies, metabolic diseases and hematologic diseases such as α-thalassemia. This review provides an overview of syndromic and single gene disorders associated with fetal pleural effusion that is useful for genetic counseling and fetal therapy at prenatal diagnosis of fetal pleural effusion.

Chromosomal abnormalities associated with fetal pleural effusion (I): General overview

Fetal pleural effusion has been reported to be associated with chromosomal abnormalities, genetic syndromes, obstructive uropathy, lymphatic vessel abnormalities such as Noonan syndrome, RASopathy and congenital lymphatic anomalies, thoracic cavity defects, Rh or ABO incompatibility, non-immune hydrops fetalis, infections, congenital cardiac anomalies, metabolic diseases and hematologic diseases such as α-thalassemia. This review provides an overview of chromosomal abnormalities associated with fetal pleural effusion which is useful for genetic counseling and fetal therapy at prenatal diagnosis of fetal pleural effusion.

Chromosomal abnormalities associated with fetal pleural effusion (II): Specific and non-specific chromosome aberrations

Fetal pleural effusion has been reported to be associated with chromosomal abnormalities, genetic syndromes, obstructive uropathy, lymphatic vessel abnormalities such as Noonan syndrome, RASopathy and congenital lymphatic anomalies, thoracic cavity defects, Rh or ABO incompatibility, non-immune hydrops fetalis, infections, congenital cardiac anomalies, metabolic diseases and hematologic diseases such as α-thalassemia. This review provides a comprehensive view of specific and non-specific chromosome aberrations associated with fetal pleural effusion which is useful for genetic counseling and fetal therapy at prenatal diagnosis of fetal pleural effusion.

A novel RYR1 variant in an infant with a unique fetal presentation of central core disease

Ryanodine receptor type 1-related disorder (RYR1-RD) is the most common subgroup of congenital myopathies with a wide phenotypic spectrum ranging from mild hypotonia to lethal fetal akinesia. Genetic testing for myopathies is imperative as the diagnosis informs counseling regarding prognosis and recurrence risk, treatment options, monitoring, and clinical management. However, diagnostic challenges exist as current options are limited to clinical suspicion prompting testing including: single gene sequencing or familial variant testing, multi-gene panels, exome, genome sequencing, and invasive testing including muscle biopsy. The timing of diagnosis is of great importance due to the association of RYR1-RD with malignant hyperthermia (MH). MH is a hypermetabolic crisis that occurs secondary to excessive calcium release in muscles, leading to systemic effects that can progress to shock and death if unrecognized. Given the association of MH with pathogenic variants in RYR1, a diagnosis of RYR1-RD necessitates an awareness of medical team to avoid potentially triggering agents. We describe a case of a unique fetal presentation with bilateral diaphragmatic eventrations who had respiratory failure, dysmorphic facial features, and profound global hypotonia in the neonatal period. The diagnosis was made at several months of age, had direct implications on her clinical care related to anticipated need to long-term ventilator support, and ultimately death secondary an arrhythmia as a result of suspected MH. Our report reinforces the importance of having high suspicion for a genetic syndrome and pursuing early, rapid exome or genome sequencing as first line testing in critically ill neonatal intensive care unit patients and further evaluating the pathogenicity of a variant of uncertain significance in the setting of a myopathic phenotype.

Diagnostic yield from prenatal exome sequencing for non-immune hydrops fetalis: A systematic review and meta-analysis

Non-immune hydrops fetalis (NIHF) has multiple genetic etiologies diagnosable by exome sequencing (ES). We evaluated the yield of prenatal ES for NIHF, and the contribution of additional clinical findings and history. Systematic review was performed with PROSPERO tag 232951 using CINAHL, PubMed, and Ovid MEDLINE from January 1, 2000 through December 1, 2021. Selected studies performed ES to augment standard prenatal diagnostic approaches. Cases meeting a strict NIHF phenotype were tabulated with structured data imputed from papers or requested from authors. Genetic variants and diagnostic outcomes were harmonized across studies using current ACMG and ClinGen variant classification guidelines. Thirty-one studies reporting 445 NIHF cases had a 37% (95% CI: 32%-41%) diagnostic rate. There was no significant difference between isolated NIHF and NIHF with fetal malformations or between recurrent and simplex cases. Diagnostic rate was higher for consanguineous than non-consanguineous cases. Disease categories included RASopathies (24%), neuromuscular (21%), metabolic (17%), lymphatic (13%), other syndromes (9%), cardiovascular (5%), hematologic (2%), skeletal (2%), and other categories (7%). Inheritance patterns included recessive (55%), dominant (41%), and X-linked (4%). ES should be considered in the diagnostic workup of NIHF with and without associated ultrasound findings regardless of history of recurrence or consanguinity.

Mutation update for the ACTN2 gene

ACTN2 encodes alpha-actinin-2, a protein expressed in human cardiac and skeletal muscle. The protein, located in the sarcomere Z-disk, functions as a link between the anti-parallel actin filaments. This important structural protein also binds N-terminal titins, and thus contributes to sarcomere stability. Previously, ACTN2 mutations have been solely associated with cardiomyopathy, without skeletal muscle disease. Recently, however, ACTN2 mutations have been associated with novel congenital and distal myopathy. Previously reported variants are in varying locations across the gene, but the potential clustering effect of pathogenic locations is not clearly understood. Further, the genotype-phenotype correlations of these variants remain unclear. Here we review the previously reported ACTN2-related molecular and clinical findings and present an additional variant, c.1840-2A>T, that further expands the mutation and phenotypic spectrum. Our results show a growing body of clinical, genetic, and functional evidence, which underlines the central role of ACTN2 in the muscle tissue and myopathy. However, limited segregation and functional data are available to support the pathogenicity of most previously reported missense variants and clear-cut genotype-phenotype correlations are currently only demonstrated for some ACTN2-related myopathies.

Intrauterine Thoracoamniotic Shunting of Fetal Hydrothorax with the Somatex Intrauterine Shunt: Intrauterine Course and Postnatal Outcome

(1) Background: Severe fetal hydrothorax can be treated by intrauterine thoracoamniotic shunting (TAS). The aim of this study was to assess perinatal outcome and complication rates of TAS with a novel Somatex intrauterine shunt. (2) Methods: This is a single-center retrospective study of all fetuses with hydrothorax treated with TAS using a Somatex shunt between 2014 and 2020. (3) Results: A total of 39 fetuses were included in the study. Mean gestational age at first intervention was 27.4 weeks (range 19–33). Of these, 51% (n = 20) of fetuses had fetal hydrops, which resolved in 65% (13/20) before delivery. The live birth rate was 97% (n = 38), and 74% (n = 29) survived the neonatal period. The rate of postnatal pulmonary complications was high, with 88% of neonates requiring any kind of ventilatory support. There were 23% (n = 9) genetic abnormalities (trisomy 21 and Noonan syndrome). (4) Conclusions: TAS with a Somatex shunt has a high technical success rate, leading to high neonatal survival rates. Pregnancy and neonatal outcome is comparable to TAS for fetal hydrothorax using different shunt types.

Fetal hydrops and the Incremental yield of Next-generation sequencing over standard prenatal Diagnostic testing (FIND) study: prospective cohort study and meta-analysis

OBJECTIVE

To determine the incremental yield of exome sequencing (ES) over chromosomal microarray analysis (CMA) or karyotyping in prenatally diagnosed non-immune hydrops fetalis (NIHF).

METHODS

A prospective cohort study (comprising an extended group of the Prenatal Assessment of Genomes and Exomes (PAGE) study) was performed which included 28 cases of prenatally diagnosed NIHF undergoing trio ES following negative CMA or karyotyping. These cases were combined with data from a systematic review of the literature. MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov databases were searched electronically (January 2000 to October 2020) for studies reporting on the incremental yield of ES over CMA or karyotyping in fetuses with prenatally detected NIHF. Inclusion criteria for the systematic review were: (i) at least two cases of NIHF undergoing sequencing; (ii) testing initiated based on prenatal ultrasound-based phenotype; and (iii) negative CMA or karyotyping result. The incremental diagnostic yield of ES was assessed in: (i) all cases of NIHF; (ii) isolated NIHF; (iii) NIHF associated with an additional fetal structural anomaly; and (iv) NIHF according to severity (i.e. two vs three or more cavities affected).

RESULTS

In the extended PAGE study cohort, the additional diagnostic yield of ES over CMA or karyotyping was 25.0% (7/28) in all NIHF cases, 21.4% (3/14) in those with isolated NIHF and 28.6% (4/14) in those with non-isolated NIHF. In the meta-analysis, the pooled incremental yield based on 21 studies (306 cases) was 29% (95% CI, 24-34%; P < 0.00001; I²  = 0%) in all NIHF, 21% (95% CI, 13-30%; P < 0.00001; I²  = 0%) in isolated NIHF and 39% (95% CI, 30-49%; P < 0.00001; I²  = 1%) in NIHF associated with an additional fetal structural anomaly. In the latter group, congenital limb contractures were the most prevalent additional structural anomaly associated with a causative pathogenic variant, occurring in 17.3% (19/110) of cases. The incremental yield did not differ significantly according to hydrops severity. The most common genetic disorders identified were RASopathies, occurring in 30.3% (27/89) of cases with a causative pathogenic variant, most frequently due to a PTPN11 variant (44.4%; 12/27). The predominant inheritance pattern in causative pathogenic variants was autosomal dominant in monoallelic disease genes (57.3%; 51/89), with most being de novo (86.3%; 44/51).

CONCLUSIONS

Use of prenatal next-generation sequencing in both isolated and non-isolated NIHF should be considered in the development of clinical pathways. Given the wide range of potential syndromic diagnoses and heterogeneity in the prenatal phenotype of NIHF, exome or whole-genome sequencing may prove to be a more appropriate testing approach than a targeted gene panel testing strategy. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.