Fetal pleural effusion: Contemporary methods of genetic evaluation

Risk of Genetic Abnormality in Fetuses With Unilateral Versus Bilateral Pleural Effusions

OBJECTIVE

Fetal pleural effusions are often associated with underlying genetic etiologies; however, data describing the incidence of genetic abnormalities are limited. We evaluated the rate of genetic abnormalities in pregnancies affected by primary unilateral and bilateral fetal pleural effusion.

METHODS

This study is a retrospective cohort study of all patients evaluated at our center with a prenatal diagnosis of primary fetal pleural effusion from 2010 to 2022. All patients with a singleton pregnancy and diagnostic genetic testing were included. Patients were separated into two groups: those with unilateral or bilateral effusions at initial diagnosis. Genetic diagnoses, fetal interventions, and pregnancy outcomes were evaluated.

RESULTS

Among 229 cases of fetal pleural effusion, 30 met the inclusion criteria. Unilateral effusion was seen in 14/30 cases (47%) and bilateral effusion in 16/30 cases (53%). Genetic abnormalities were present in 7/14 (50%) unilateral and 2/14 (14%) bilateral effusions (p = 0.046). Cases of bilateral effusion had higher rates of fetal intervention with thoracoamniotic shunt (69% vs. 14%; p = 0.004) and earlier delivery (33 vs. 36 weeks, p = 0.002). Bilateral effusions were found to have higher rates of respiratory distress syndrome and neonatal death (p = 0.03 and 0.04), respectively.

CONCLUSION

Pregnancies affected by primary fetal pleural effusion have a high rate of genetic abnormalities. Although bilateral fetal pleural effusions have worse perinatal outcomes, unilateral fetal pleural effusions have a high rate of genetic diagnosis and both unilateral and bilateral fetal pleural effusions warrant comprehensive prenatal genetic testing.

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.

LZTR1 molecular genetic overlap with clinical implications for Noonan syndrome and schwannomatosis

Background

Noonan syndrome (NS) is a genetic disorder characterized by developmental delays, typical facial gestalt and cardiovascular defects. LZTR1 variants have been recently described in patients with NS and schwannomatosis, but the association, inheritance pattern and management strategy has not been fully elucidated. Here, we review the contribution of LZTR1 in NS and describe a patient with a novel, likely pathogenic variant in LZTR1.

Case presentation

A female patient was diagnosed with clinical NS at 8 months of age. She presented in adulthood when a brain and spine MRI identified plexiform neurofibromas; however, she did not meet the clinical criteria for Neurofibromatosis type 1. No pathogenic variants were identified through molecular genetic analysis of NF1, SPRED1 and a multigene NS panel. Whole exome sequencing at age 23 identified a novel de novo likely pathogenic heterozygous variant in the LZTR1 gene denoted as c.743G>A (p.Gly248Glu). Serial MRIs have shown stable imaging findings and the patient is being followed clinically by cardiology, neurology and medical genetics.

Conclusions

We identified a novel mutation in the LZTR1 gene, not previously reported in association with NS. This report provides additional evidence to support for the assessment of schwannomatosis in patients with LZTR1-NS and may have overlap with Neurofibromatosis type 1.

Prenatal phenotype of Kabuki syndrome: A case series and literature review

OBJECTIVES

Kabuki syndrome (KS) is a genetic disorder characterized by intellectual disability, facial dysmorphism and congenital anomalies. We aim to investigate the prenatal features of fetuses with KS and to provide a comprehensive review of the literature on prenatal sonographic abnormalities associated with KS.

METHODS

We retrospectively reviewed the prenatal ultrasound findings of all mothers of children with molecularly confirmed KS in Hong Kong, between 1991 and 2019. We also performed systematic review of the literature to identify studies on the prenatal findings in KS.

RESULTS

We identified 11 cases with KS with detectable fetal ultrasound findings ranging from no detectable abnormalities to a variety of non-specific findings including increased nuchal translucency, pleural effusion, cardiac anomalies, renal anomalies, intrauterine growth restriction, polyhydramnios, oligohydramnios and single umbilical artery. In combining our cases with the 77 cases published, 42 (50.6%) of them had more than one abnormal antenatal ultrasound finding. The most frequent ultrasound features observed were cardiac anomalies (49.4%), followed by polyhydramnios (28.9%), genitourinary anomalies (26.5%), single umbilical artery (15.7%), intrauterine growth restriction (14.5%) and hydrops fetalis/pleural effusion/ascites (12.0%).

CONCLUSIONS

These cases demonstrate the prenatal phenotypic heterogeneity associated with KS. Although the ultrasound abnormalities are non-specific, KS should be considered in the differential diagnosis when these fetal findings following normal microarray analysis/karyotyping.

A homozygous variant in growth and differentiation factor 2 (GDF2) may cause lymphatic dysplasia with hydrothorax and nonimmune hydrops fetalis

The etiology of nonimmune hydrops fetalis is extensive and includes genetic disorders. We describe a term-born female neonate with late onset extensive nonimmune hydrops, that is, polyhydramnios, edema, and congenital bilateral chylothorax. This newborn was successfully treated with repetitive thoracocentesis, total parenteral feeding, octreotide intravenously and finally surgical pleurodesis and corticosteroids. A genetic cause seemed plausible as the maternal history revealed a fatal nonimmune hydrops fetalis. A homozygous truncating variant in GDF2 (c.451C>T, p.(Arg151*)) was detected with exome sequencing. Genetic analysis of tissue obtained from the deceased fetal sibling revealed the same homozygous variant. The parents and two healthy siblings were heterozygous for the GDF2 variant. Skin and lung biopsies in the index patient, as well as the revised lung biopsy of the deceased fetal sibling, showed lymphatic dysplasia and lymphangiectasia. To the best of our knowledge, this is the first report of an association between a homozygous variant in GDF2 with lymphatic dysplasia, hydrothorax and nonimmune hydrops fetalis.

The utility of exome sequencing for fetal pleural effusions

OBJECTIVE

We sought to evaluate the performance of exome sequencing (ES) in determining an underlying genetic etiology for cases of fetal pleural effusions.

STUDY DESIGN

We examined a prospective cohort series of fetal pleural effusions visualized sonographically between 1 April 2016 and 31 August 2017. Fetal pleural effusions attributed to twin sharing, anemia, or structural anomalies were excluded, as were all cases with a genetic diagnosis established by karyotype or chromosomal microarray analysis. The remaining cases with pleural effusions of unclear etiology were offered ES. ES was performed by clinical sequencing and/or sequencing under the Baylor-Hopkins Center for Mendelian Genomics' (BHCMG) research platform. All cases were evaluated for novel genes or phenotypic expansion of disease-causing genes.

RESULTS

ES was performed on six probands affected by pleural effusions. A pathogenic variant was identified in one case (16.7%). Four additional cases had variants of uncertain significance (VUS) in candidate genes of pathological interest. Neither clinical nor candidate genes were evident in the final case.

CONCLUSION

ES should be considered in the evaluation of prenatally detected idiopathic pleural effusions when other diagnostic workup for a genetic etiology has failed.