Pathogenetics of alveolar capillary dysplasia with misalignment of pulmonary veins

Genetic burden in neonatal and pediatric-onset pulmonary hypertension: A single-center retrospective study using exome sequencing in a Chinese population

OBJECTIVE

This single-center retrospective study aimed to investigate the genetic factors contributing to neonatal and pediatric pulmonary hypertension in a Chinese population using trio whole-exome sequencing (trio-WES).

METHOD

This retrospective analysis reviewed the clinical and genetic profiles of children under 18 years of age diagnosed with pulmonary hypertension between March 2017 and March 2022. The diagnosis of pediatric pulmonary hypertension was confirmed through echocardiography and catheterization. Trio-WES was performed on the patients and their parents after obtaining informed consent.

RESULTS

A total of 51 children with neonatal and pediatric pulmonary hypertension were included, comprising 20 with pediatric pulmonary arterial hypertension and 31 with persistent pulmonary hypertension of the newborn. Trio-WES detected 16 pathogenic or likely pathogenic variants in 14 patients across ten genes, including: BMPR2 (n = 2), CHD7 (n = 2), FOXF1 (n = 2), MED13L (n = 1), TNNI3 (n = 2), ALMS1 (n = 1), KMT2D (n = 2), NKX2-1 (n = 1), NONO (n = 1), and CACNA1E (n = 1). In addition, two patients exhibited de novo pathogenic copy number variations.

CONCLUSION

Our findings demonstrate the significant diagnostic value of trio-WES in pediatric pulmonary hypertension, supporting its recommendation for these patients.

Alveolar capillary dysplasia with misalignment of the pulmonary veins: A surgical lung biopsy and autopsy in a full-term newborn

Alveolar capillary dysplasia with misalignment of the pulmonary veins (ACD/MPV) is a rare and lethal interstitial lung disorder, caused by a congenital abnormality affecting the development of the parenchyma and pulmonary vessels. We report the case of a newborn at the end of 40 weeks of pregnancy, who showed no cardiopulmonary anomalies in prenatal control ultrasounds. However, after delivery, pulmonary hypertension and hypoxemic respiratory failure became apparent. She died after 12 days from refractory hemodynamic and respiratory failure despite intensive therapy. A surgical lung biopsy and clinical autopsy were performed, both revealing the same histopathological signs consistent with this disorder. In our case, the findings of digestive and genital malformations, together with the genetic result of the alteration in the FOXF1 gene, led us to conclude the definitive diagnosis of alveolar capillary dysplasia.

Role of Forkhead box F1 in the Pathobiology of Pulmonary Arterial Hypertension

Rationale

Approximately 80% of patients with non-familial pulmonary arterial hypertension (PAH) lack identifiable pathogenic genetic variants. While most genetic studies of PAH have focused on predicted loss-of-function variants, recent approaches have identified ultra-rare missense variants associated with the disease. FOXF1 encodes a highly conserved transcription factor, essential for angiogenesis and vasculogenesis in human and mouse lungs.

Objectives

We identified a rare FOXF1 missense coding variant in two unrelated probands with PAH. FOXF1 is an evolutionarily conserved transcription factor required for lung vascular development and vascular integrity. Our aims were to determine the frequency of FOXF1 variants in larger PAH cohorts compared to the general population, study FOXF1 expression in explanted lung tissue from PAH patients versus control (failed-donor) lungs, and define potential downstream targets linked to PAH development.

Methods

Three independent, international, multicenter cohorts were analyzed to evaluate the frequency of FOXF1 rare variants. Various composite prediction models assessed the deleteriousness of individual variants. Bulk RNA sequencing datasets from human explanted lung tissues were compared to failed-donor controls to determine FOXF1 expression. Bioinformatic tools identified putative FOXF1 binding targets, which were orthogonally validated using mouse ChIP-seq datasets.

Measurements and Main Results

Seven novel or ultra-rare missense coding variants were identified across three patient cohorts in different regions of the FOXF1 gene, including the DNA binding domain. FOXF1 expression was dysregulated in PAH lungs, correlating with disease severity. Histological analysis showed heterogeneous FOXF1 expression, with the lowest levels in phenotypically abnormal endothelial cells within complex vascular lesions in PAH samples. A hybrid bioinformatic approach identified FOXF1 downstream targets potentially involved in PAH pathogenesis, including BMPR2 .

Conclusions

Large genomic and transcriptomic datasets suggest that decreased FOXF1 expression or predicted dysfunction is associated with PAH.

Interstitial lung disease as an indication for pediatric lung transplant

Interstitial lung disease can be an indication for lung transplant at any age, but it is a particularly common indication for lung transplant in infants. Nevertheless, not all interstitial lung diseases will lead to lung transplant in childhood. Genetic testing has aided the identification of these diseases in children. In severely affected patients, however, definitive diagnosis is not always necessary to consider referral to a transplant center. At experienced transplant centers, a multidisciplinary team educates patient families and aids in the transplant evaluation of children with interstitial lung disease. Children who have undergone transplant require lifetime immunosuppression and close surveillance, but can enjoy good quality of life for years following surgery.

Practical Approach to Congenital Anomalies of the Kidneys: Focus on Anomalies With Insufficient or Abnormal Nephron Development: Renal Dysplasia, Renal Hypoplasia, and Renal Tubular Dysgenesis

Congenital anomalies of the kidney and urinary tract (CAKUT) accounts for up to 30% of antenatal congenital anomalies and is the main cause of kidney failure in children worldwide. This review focuses on practical approaches to CAKUT, particularly those with insufficient or abnormal nephron development, such as renal dysplasia, renal hypoplasia, and renal tubular dysgenesis. The review provides insights into the histological features, pathogenesis, mechanisms, etiologies, antenatal and postnatal presentation, management, and prognosis of these anomalies. Differential diagnoses are discussed as several syndromes may include CAKUT as a phenotypic component and renal dysplasia may occur in some ciliopathies, tumor predisposition syndromes, and inborn errors of metabolism. Diagnosis and genetic counseling for CAKUT are challenging, due to the extensive variability in presentation, genetic and phenotypic heterogeneity, and difficulties to assess postnatal lung and renal function on prenatal imaging. The review highlights the importance of perinatal autopsy and pathological findings in surgical specimens to establish the diagnosis and prognosis of CAKUT. The indications and the type of genetic testing are discussed. The aim is to provide essential insights into the practical approaches, diagnostic processes, and genetic considerations offering valuable guidance for pediatric and perinatal pathologists.

Lung biopsy in the diagnosis and management of chILD

Children's interstitial and diffuse lung disease (chILD) comprises a large number of diverse entities ranging from disorders of lung development, maturation and function unique in infancy to immune-mediated, environmental, vascular and other conditions overlapping with adult disease. Pathologic evaluation of the lung has played a central role in characterizing many of these disorders, resulting in revised nomenclature and classifications to help guide clinical management(1-4). Technological advancements are rapidly uncovering genetic and molecular underpinnings of these conditions, as well as widening the phenotypes which bridge adult disease, often reducing the perceived need for diagnostic lung biopsy. As such the decision to get a lung biopsy in chILD is frequently for rapid ascertainment of disease in a critically ill child or when clinical presentation, imaging and laboratory studies fail to provide a cohesive diagnosis needed for treatment. While there have been modifications in surgical procedures for lung biopsy that minimize postoperative morbidity, it remains a high-risk invasive procedure, especially in a medically complex patient(5). Thus, it is essential that the lung biopsy be handled properly to maximize diagnostic yield, including close communication between the clinician, radiologist, surgeon, and pathologist before biopsy to determine best sampling site(s) and prioritization of tissue utilization. This review provides an overview of optimal handling and evaluation of a surgical lung biopsy for suspected chILD, with emphasis on specific conditions in which pathologic features play a critical role in providing an integrated diagnosis and guiding management.

Beyond Bronchopulmonary Dysplasia: A Comprehensive Review of Chronic Lung Diseases in Neonates

In neonates, pulmonary diseases such as bronchopulmonary dysplasia and other chronic lung diseases (CLDs) pose significant challenges due to their complexity and high degree of morbidity and mortality. This review discusses the etiology, pathophysiology, clinical presentation, and diagnostic criteria for these conditions, as well as current management strategies. The review also highlights recent advancements in understanding the pathophysiology of these diseases and evolving strategies for their management, including gene therapy and stem cell treatments. We emphasize how supportive care is useful in managing these diseases and underscore the importance of a multidisciplinary approach. Notably, we discuss the emerging role of personalized medicine, enabled by advances in genomics and precision therapeutics, in tailoring therapy according to an individual's genetic, biochemical, and lifestyle factors. We conclude with a discussion on future directions in research and treatment, emphasizing the importance of furthering our understanding of these conditions, improving diagnostic criteria, and exploring targeted treatment modalities. The review underscores the need for multicentric and longitudinal studies to improve preventative strategies and better understand long-term outcomes. Ultimately, a comprehensive, innovative, and patient-centered approach can enhance the quality of care and outcomes for neonates with CLDs.

Identification of endothelial and mesenchymal FOXF1 enhancers involved in alveolar capillary dysplasia

Mutations in the FOXF1 gene, a key transcriptional regulator of pulmonary vascular development, cause Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins, a lethal lung disease affecting newborns and infants. Identification of new FOXF1 upstream regulatory elements is critical to explain why frequent non-coding FOXF1 deletions are linked to the disease. Herein, we use multiome single-nuclei RNA and ATAC sequencing of mouse and human patient lungs to identify four conserved endothelial and mesenchymal FOXF1 enhancers. We demonstrate that endothelial FOXF1 enhancers are autoactivated, whereas mesenchymal FOXF1 enhancers are regulated by EBF1 and GLI1. The cell-specificity of FOXF1 enhancers is validated by disrupting these enhancers in mouse embryonic stem cells using CRISPR/Cpf1 genome editing followed by lineage-tracing of mutant embryonic stem cells in mouse embryos using blastocyst complementation. This study resolves an important clinical question why frequent non-coding FOXF1 deletions that interfere with endothelial and mesenchymal enhancers can lead to the disease.

Pulmonary Hypertension in Developmental Lung Diseases

Diverse genetic developmental lung diseases can present in the neonatal period with hypoxemic respiratory failure, often associated with with pulmonary hypertension. Intractable hypoxemia and lack of sustained response to medical management should increase the suspicion of a developmental lung disorder. Genetic diagnosis and lung biopsy are helpful in establishing the diagnosis. Early diagnosis can result in optimizing management and redirecting care if needed. This article reviews normal lung development, various developmental lung disorders that can result from genetic abnormalities at each stage of lung development, their clinical presentation, management, prognosis, and differential diagnoses.

Deciphering Endothelial and Mesenchymal Organ Specification in Vascularized Lung and Intestinal Organoids

To investigate the co-development of vasculature, mesenchyme, and epithelium crucial for organogenesis and the acquisition of organ-specific characteristics, we constructed a human pluripotent stem cell-derived organoid system comprising lung or intestinal epithelium surrounded by organotypic mesenchyme and vasculature. We demonstrated the pivotal role of co-differentiating mesoderm and endoderm via precise BMP regulation in generating multilineage organoids and gut tube patterning. Single-cell RNA-seq analysis revealed organ specificity in endothelium and mesenchyme, and uncovered key ligands driving endothelial specification in the lung (e.g., WNT2B and Semaphorins) or intestine (e.g., GDF15). Upon transplantation under the kidney capsule in mice, these organoids further matured and developed perfusable human-specific sub-epithelial capillaries. Additionally, our model recapitulated the abnormal endothelial-epithelial crosstalk in patients with FOXF1 deletion or mutations. Multilineage organoids provide a unique platform to study developmental cues guiding endothelial and mesenchymal cell fate determination, and investigate intricate cell-cell communications in human organogenesis and disease.

Highlights

BMP signaling fine-tunes the co-differentiation of mesoderm and endoderm.The cellular composition in multilineage organoids resembles that of human fetal organs.Mesenchyme and endothelium co-developed within the organoids adopt organ-specific characteristics.Multilineage organoids recapitulate abnormal endothelial-epithelial crosstalk in FOXF1-associated disorders.

Multilamellated Basement Membranes in the Capillary Network of Alveolar Capillary Dysplasia

A minimal diffusion barrier is key to the pulmonary gas exchange. In alveolar capillary dysplasia (ACD), a rare genetically driven disease of early infancy, this crucial fibrovascular interface is compromised while the underlying pathophysiology is insufficiently understood. Recent in-depth analyses of vascular alterations in adult lung disease encouraged researchers to extend these studies to ACD and compare the changes of the microvasculature. Lung tissue samples of children with ACD (n = 12), adults with non-specific interstitial pneumonia (n = 12), and controls (n = 20) were studied using transmission electron microscopy, single-gene sequencing, immunostaining, exome sequencing, and broad transcriptome profiling. In ACD, pulmonary capillary basement membranes were hypertrophied, thickened, and multilamellated. Transcriptome profiling revealed increased CDH5, COL4A1, COL15A1, PTK2B, and FN1 and decreased VIT expression, confirmed by immunohistochemistry. In contrast, non-specific interstitial pneumonia samples showed a regular basement membrane architecture with preserved VIT expression but also increased COL15A1+ vessels. This study provides insight into the ultrastructure and pathophysiology of ACD. The lack of normally developed lung capillaries appeared to cause a replacement by COL15A1+ vessels, a mechanism recently described in interstitial lung disease. The VIT loss and FN1 overexpression might contribute to the unique appearance of basement membranes in ACD. Future studies are needed to explore the therapeutic potential of down-regulating the expression of FN1 and balancing VIT deficiency.

Twins with alveolar capillary dysplasia with misalignment of pulmonary veins: Strategies for diagnosis and management

We present a case of dichorionic-diamniotic twin females who developed hypoxemic respiratory failure. They were ultimately diagnosed by lung biopsy with alveolar capillary dysplasia with misalignment of pulmonary veins. This case highlights a practical approach to reaching a diagnosis in infants with suspected developmental lung disease.

Reduced FOXF1 links unrepaired DNA damage to pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease in which pulmonary arterial (PA) endothelial cell (EC) dysfunction is associated with unrepaired DNA damage. BMPR2 is the most common genetic cause of PAH. We report that human PAEC with reduced BMPR2 have persistent DNA damage in room air after hypoxia (reoxygenation), as do mice with EC-specific deletion of Bmpr2 (EC-Bmpr2-/-) and persistent pulmonary hypertension. Similar findings are observed in PAEC with loss of the DNA damage sensor ATM, and in mice with Atm deleted in EC (EC-Atm-/-). Gene expression analysis of EC-Atm-/- and EC-Bmpr2-/- lung EC reveals reduced Foxf1, a transcription factor with selectivity for lung EC. Reducing FOXF1 in control PAEC induces DNA damage and impaired angiogenesis whereas transfection of FOXF1 in PAH PAEC repairs DNA damage and restores angiogenesis. Lung EC targeted delivery of Foxf1 to reoxygenated EC-Bmpr2-/- mice repairs DNA damage, induces angiogenesis and reverses pulmonary hypertension.

Clinical Relevance of Rapid FOXF1-Targeted Sequencing in Patients Suspected of Alveolar Capillary Dysplasia With Misalignment of Pulmonary Veins

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a lethal congenital lung disorder that presents shortly after birth with respiratory failure and therapy-resistant pulmonary hypertension. It is associated with heterozygous point mutations and genomic deletions that involve the FOXF1 gene or its upstream regulatory region. Patients are unresponsive to the intensive treatment regimens and suffer unnecessarily because ACDMPV is not always timely recognized and histologic diagnosis is invasive and time consuming. Here, we demonstrate the usefulness of a noninvasive, fast genetic test for FOXF1 variants that we previously developed to rapidly diagnose ACDMPV and reduce the time of hospitalization.

Further refinement of the differentially methylated distant lung-specific FOXF1 enhancer in a neonate with alveolar capillary dysplasia

Heterozygous SNVs or CNV deletions involving the FOXF1 gene, or its distant enhancer, are causative for 80-90% of cases of alveolar capillary dysplasia with misalignment of pulmonary veins. Recently, we proposed bimodal structure and parental functional dimorphism of the lung-specific FOXF1 enhancer, with Unit 1 having higher activity on the paternal chr16 and Unit 2 on the maternal chr16. Here, we describe a novel unusually sized pathogenic de novo copy-number variant deletion involving a portion of the FOXF1 enhancer on maternal chr16 that implies narrowing Unit 2 to an essential ~ 9-kb segment. Using a restrictase-based assay, we found that this enhancer segment is weakly methylated at ApT adenine, with about twice the frequency of methylation on the maternal versus paternal chr16. Our data provide further insight into the FOXF1 enhancer structure and function.

A Small De Novo CNV Deletion of the Paternal Copy of FOXF1, Leaving lncRNA FENDRR Intact, Provides Insight into Their Bidirectional Promoter Region

Pathogenic single-nucleotide variants (SNVs) and copy-number variant (CNV) deletions involving the FOXF1 transcription factor gene or CNV deletions of its distant lung-specific enhancer are responsible for alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), a rarely diagnosed lethal lung developmental disorder in neonates. In contrast to SNVs within FOXF1 and CNV deletions involving only the FOXF1 enhancer, larger-sized deletions involving FOXF1 and the adjacent, oppositely oriented lncRNA gene FENDRR have additionally been associated with hypoplastic left heart syndrome and single umbilical artery (SUA). Here, in an ACDMPV infant without any congenital heart defect or SUA, we identified a small 5 kb CNV deletion that removed the paternal allele of FOXF1 and its promoter, leaving FENDRR and its promoter intact. Reporter assay in the IMR-90 fetal cell line implied that the deletion may indeed not have significantly affected FENDRR expression. It also showed a polarization of the FOXF1-FENDRR inter-promoter region consisting of its ability to increase the transcription of FENDRR but not FOXF1. Interestingly, this transcription-stimulating activity was suppressed in the presence of the FOXF1 promoter. Our data shed more light on the interactions between neighboring promoters of FOXF1-FENDRR and possibly other divergently transcribed mRNA-lncRNA gene pairs.

Single Cell Multiomics Identifies Cells and Genetic Networks Underlying Alveolar Capillary Dysplasia

Rationale: Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a lethal developmental disorder of lung morphogenesis caused by insufficiency of FOXF1 (forkhead box F1) transcription factor function. The cellular and transcriptional mechanisms by which FOXF1 deficiency disrupts human lung formation are unknown. Objectives: To identify cell types, gene networks, and cell-cell interactions underlying the pathogenesis of ACDMPV. Methods: We used single-nucleus RNA and assay for transposase-accessible chromatin sequencing, immunofluorescence confocal microscopy, and RNA in situ hybridization to identify cell types and molecular networks influenced by FOXF1 in ACDMPV lungs. Measurements and Main Results: Pathogenic single-nucleotide variants and copy-number variant deletions involving the FOXF1 gene locus in all subjects with ACDMPV (n = 6) were accompanied by marked changes in lung structure, including deficient alveolar development and a paucity of pulmonary microvasculature. Single-nucleus RNA and assay for transposase-accessible chromatin sequencing identified alterations in cell number and gene expression in endothelial cells (ECs), pericytes, fibroblasts, and epithelial cells in ACDMPV lungs. Distinct cell-autonomous roles for FOXF1 in capillary ECs and pericytes were identified. Pathogenic variants involving the FOXF1 gene locus disrupt gene expression in EC progenitors, inhibiting the differentiation or survival of capillary 2 ECs and cell-cell interactions necessary for both pulmonary vasculogenesis and alveolar type 1 cell differentiation. Loss of the pulmonary microvasculature was associated with increased VEGFA (vascular endothelial growth factor A) signaling and marked expansion of systemic bronchial ECs expressing COL15A1 (collagen type XV α 1 chain). Conclusions: Distinct FOXF1 gene regulatory networks were identified in subsets of pulmonary endothelial and fibroblast progenitors, providing both cellular and molecular targets for the development of therapies for ACDMPV and other diffuse lung diseases of infancy.

Prenatal Detection of a FOXF1 Deletion in a Fetus with ACDMPV and Hydronephrosis

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a lethal lung developmental disorder caused by the arrest of fetal lung formation, resulting in neonatal death due to acute respiratory failure and pulmonary arterial hypertension. Heterozygous single-nucleotide variants or copy-number variant (CNV) deletions involving the FOXF1 gene and/or its lung-specific enhancer are found in the vast majority of ACDMPV patients. ACDMPV is often accompanied by extrapulmonary malformations, including the gastrointestinal, cardiac, or genitourinary systems. Thus far, most of the described ACDMPV patients have been diagnosed post mortem, based on histologic evaluation of the lung tissue and/or genetic testing. Here, we report a case of a prenatally detected de novo CNV deletion (~0.74 Mb) involving the FOXF1 gene in a fetus with ACDMPV and hydronephrosis. Since ACDMPV is challenging to detect by ultrasound examination, the more widespread implementation of prenatal genetic testing can facilitate early diagnosis, improve appropriate genetic counselling, and further management.

Changing populations being treated with ECMO in the neonatal period - who are the others?

Extracorporeal life support via extracorporeal membrane oxygenation (ECMO) has served the sickest of neonates for almost 50 years. Naturally, the characteristics of neonates receiving ECMO have changed. Advances in care have averted the need for ECMO for some, while complex cases with uncertain outcomes, previously not eligible for ECMO, are now considered. Characterizing the disease states and outcomes for neonates on ECMO is challenging as many infants do not fall into classic categories, i.e. meconium aspiration syndrome (MAS), respiratory distress syndrome (RDS), or congenital diaphragmatic hernia (CDH). Since 2017, over one third of neonatal respiratory ECMO runs reported to the Extracorporeal Life Support Organization Registry are grouped as Other, a catch-all that encompasses those with a diagnosis not included in the classic categories. This review summarizes the historical neonatal ECMO population, reviews advances in therapy and technology impacting neonatal care, and addresses the unknowns in the ever-growing category of Other.

Haploinsufficiencies of FOXF1, FOXC2 and FOXL1 genes originated from deleted 16q24.1q24.2 fragment related with alveolar capillary dysplasia with misalignment of pulmonary veins and lymphedema-distichiasis syndrome: relationship to phenotype

Objective

We describe a fetus with a 2.12-Mb terminal deleted fragment in 16q associated with alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) and lymphedema-distichiasis syndrome (LDS) and intend to provide a comprehensive prenatal management strategy for the fetuses with ACDMPV and LDS through reviewing other similar published studies.

Methods

The fetus presented a series of diverse structural malformations including congenital cardiovascular, genitourinary and gastro-intestinal anomalies in ultrasound at 23 + 5 weeks of gestation (GA). Amniocentesis was conducted for karyotype analysis and copy number variation sequencing (CNV-seq) after informed consent.

Results

The fetal karyotype was 46,XX, however the result of CNV-seq showed an approximately 2.12-Mb deletion in 16q24.1q24.2 (85220000-87340000) × 1 indicating pathogenicity.

Conclusion

Genomic testing should be recommend as a first line diagnostic tool for suspected ACDMPV and/or LDS or other genetic syndromes for the fetuses with structural abnormalities in clinical practice.

Variable expressivity in a four-generation ACDMPV family with a non-coding hypermorphic SNV in trans to the frameshifting FOXF1 variant

Heterozygous single nucleotide variants (SNVs) or copy-number variant deletions involving FOXF1 or its distant lung-specific enhancer on chromosome 16q24.1 have been identified in 80-90% of patients with Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), a lethal neonatal lung developmental disorder. We describe a four-generation family with a deceased ACDMPV neonate, her sibling from the electively terminated pregnancy, healthy mother with a history of pulmonary arterial hypertension (PAH), an unaffected aunt, an aunt deceased due to findings consistent with ACDMPV, and a reportedly unaffected grandmother, all with the frameshifting variant c.881_902dup (p.Gly302Profs*46) in FOXF1, and a deceased great-grandmother with a history of PAH. Genome sequencing analyses in the proband's unaffected mother revealed a non-coding putative regulatory SNV rs560517434-A within the lung-specific distant FOXF1 enhancer in trans to the FOXF1 frameshift mutation. Functional testing of this variant using an in vitro luciferase reporter assay showed that it increased FOXF1 promoter activity 10-fold. Our studies further demonstrate that non-coding SNVs in the FOXF1 enhancer region can rescue the lethal ACDMPV phenotype and support the compound inheritance gene dosage model.

High-level gonosomal mosaicism for a pathogenic non-coding CNV deletion of the lung-specific FOXF1 enhancer in an unaffected mother of an infant with ACDMPV

BACKGROUND

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) results from haploinsufficiency of the mesenchymal transcription factor FOXF1 gene. To date, only one case of an ACDMPV-causative CNV deletion inherited from a very-low level somatic mosaic mother has been reported.

METHODS

Clinical, histopathological, and molecular studies, including whole genome sequencing, chromosomal microarray analysis, qPCR, and Sanger sequencing, followed by in vitro fertilization (IVF) with preimplantation genetic testing (PGT) were used to study a family with a deceased neonate with ACDMPV.

RESULTS

A pathogenic CNV deletion of the lung-specific FOXF1 enhancer in the proband was found to be inherited from an unaffected mother, 36% mosaic for this deletion in her peripheral blood cells. The qPCR analyses of saliva, buccal cells, urine, nail, and hair samples revealed 19%, 18%, 15%, 19%, and 27% variant allele fraction, respectively, indicating a high recurrence risk. Grandparental studies revealed that the deletion arose on the mother's paternal chromosome 16. PGT studies revealed 44% embryos with the deletion, reflecting high-level germline mosaicism.

CONCLUSION

Our data further demonstrate the importance of parental testing in ACDMPV families and reproductive usefulness of IVF with PGT in families with high-level parental gonosomal mosaicism.

Ultrasound findings in neonates with alveolar capillary dysplasia with misalignment of the pulmonary veins: report of two cases

Alveolar capillary dysplasia with misalignment of the pulmonary veins (ACDMPV) is a rare congenital pulmonary disease that affects newborns. Most patients with ACDMPV are born at full term and are healthy. The main clinical manifestations are refractory pulmonary hypertension and pulmonary failure with gastrointestinal, urinary, or cardiac malformations. ACDMPV often progresses rapidly, but no conventional biological or imaging tests other than genetic testing are available for its diagnosis. Lung biopsy is currently the gold standard for diagnosis. We herein report two cases of ACDMPV confirmed by pathological examination and discuss their ultrasonographic findings.

A Morphomolecular Approach to Alveolar Capillary Dysplasia

Alveolar capillary dysplasia (ACD) is a rare lung developmental disorder leading to persistent pulmonary arterial hypertension and fatal outcomes in newborns. The current study analyzed the microvascular morphology and the underlying molecular background of ACD. One ACD group (n = 7), one pulmonary arterial hypertension group (n = 20), and one healthy con1trol group (n = 16) were generated. Samples of histologically confirmed ACD were examined by exome sequencing and array-based comparative genomic hybridization. Vascular morphology was analyzed using scanning electron microscopy of microvascular corrosion casts. Gene expression and biological pathways were analyzed using two panels on inflammation/kinase-specific genes and a comparison analysis tool. Compartment-specific protein expression was analyzed using immunostaining. In ACD, there was an altered capillary network, a high prevalence of intussusceptive angiogenesis, and increased activity of C-X-C motif chemokine receptor 4 (CXCR4), hypoxia-inducible factor 1α (HIF1A), and angiopoietin signaling pathways compared with pulmonary arterial hypertension/healthy controls. Histologically, there was a markedly increased prevalence of endothelial tyrosine kinase receptor (TEK/TIE2)⁺ macrophages in ACD, compared with the other groups, whereas the CXCR4 ligand CXCL12 and HIF1A showed high expression in all groups. ACD is characterized by dysfunctional capillaries and a high prevalence of intussusceptive angiogenesis. The results indicate that endothelial CXCR4, HIF1A, and angiopoietin signaling as well as TIE2⁺ macrophages are crucial for the induction of intussusceptive angiogenesis and vascular remodeling. Future studies should address the use of anti-angiogenic agents in ACD, where TIE2 appears as a promising target.

Do paternal deletions involving the FOXF1 locus on chromosome 16q24.1 manifest with more severe non-lung anomalies?

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal lung developmental disorder in neonates due to heterozygous loss-of-function of the mesenchymal transcription factor gene, FOXF1. Interestingly, unlike ACDMPV-causing point mutations in FOXF1 that can be inherited from the mother or father, causative copy-number variant (CNV) deletions arise de novo and almost exclusively on chromosome 16 inherited from the mother (n = 50 vs. n = 3). Here, we describe a fourth case of a de novo paternal CNV deletion encompassing FOXF1, its neighboring long non-coding RNA gene FENDRR, and their distant lung-specific enhancer, identified in a 21-week-old fetus with tetralogy of Fallot, gastrointestinal and genitourinary abnormalities, a single umbilical artery, and patchy histopathological findings of ACDMPV in autopsy lung. We also review the ACDMPV-causative CNV deletions detected prenatally and propose that the majority of paternal deletions manifest with more severe additional non-lung abnormalities.

Microdeletion of 16q24.1-q24.2-A unique etiology of Lymphedema-Distichiasis syndrome and neurodevelopmental disorder

Interstitial deletions of 16q24.1–q24.2 are associated with alveolar capillary dysplasia, congenital renal malformations, neurodevelopmental disorders, and congenital abnormalities. Lymphedema–Distichiasis syndrome (LDS; OMIM # 153400) is a dominant condition caused by heterozygous pathogenic variants in FOXC2. Usually, lymphedema and distichiasis occur in puberty or later on, and affected individuals typically achieve normal developmental milestones. Here, we describe a boy with congenital lymphedema, distichiasis, bilateral hydronephrosis, and global developmental delay, with a de novo microdeletion of 894 kb at 16q24.1–q24.2. This report extends the phenotype of both 16q24.1–q24.2 microdeletion syndrome and of LDS. Interestingly, the deletion involves only the 3′‐UTR part of FOXC2.

Strategies for the Neonatal Lung Biopsy: Histology to Genetics

Neonatal lung biopsy guides important medical decisions when the diagnosis is not clear from prior clinical assessment, imaging, or genetic testing. Common scenarios that lead to biopsy include severe acute respiratory distress in a term neonate, pulmonary hypertension disproportionate to that expected for gestational age or known cardiac anomalies, and assessment of suspected genetic disorder based on clinical features or genetic variant of unknown significance. The differential diagnosis includes genetic developmental disorders, genetic surfactant disorders, vascular disorders, acquired infection, and meconium aspiration. This article describes pathologic patterns in the neonatal lung and correlation with molecular abnormalities, where appropriate.

Two cases of different genetic variants of alveolar capillary dysplasia associated with left-sided obstructive CHDs

Alveolar capillary dysplasia with misalignment of the pulmonary veins is an uncommon disorder that affects the lung vasculature development in the neonatal period and leads to pulmonary hypertension. We describe two patients with alveolar capillary dysplasia associated with left-sided obstructive heart defects with two different genetic variants. Our cases highlight the importance of early recognition of this disease in the setting of persistent and supra-systemic pulmonary hypertension despite surgical correction of the associated lesions. Identification of these cases will facilitate the development of a multidisciplinary approach and provide guidance to the affected families.

Genome wide DNA methylation analysis of alveolar capillary dysplasia lung tissue reveals aberrant methylation of genes involved in development including the FOXF1 locus

Background

Alveolar capillary dysplasia with or without misalignment of the pulmonary veins (ACD/MPV) is a lethal congenital lung disorder associated with a variety of heterozygous genomic alterations in the FOXF1 gene or its 60 kb enhancer. Cases without a genomic alteration in the FOXF1 locus have been described as well. The mechanisms responsible for FOXF1 haploinsufficiency and the cause of ACD/MPV in patients without a genomic FOXF1 variant are poorly understood, complicating the search for potential therapeutic targets for ACD/MPV. To investigate the contribution of aberrant DNA methylation, genome wide methylation patterns of ACD/MPV lung tissues were compared with methylation patterns of control lung tissues using the recently developed technique Methylated DNA sequencing (MeD-seq).

Results

Eight ACD/MPV lung tissue samples and three control samples were sequenced and their mutual comparison resulted in identification of 319 differentially methylated regions (DMRs) genome wide, involving 115 protein coding genes. The potentially upregulated genes were significantly enriched in developmental signalling pathways, whereas potentially downregulated genes were mainly enriched in O-linked glycosylation. In patients with a large maternal deletion encompassing the 60 kb FOXF1 enhancer, DNA methylation patterns in this FOXF1 enhancer were not significantly different compared to controls. However, two hypermethylated regions were detected in the 60 kb FOXF1 enhancer of patients harbouring a FOXF1 point mutation. Lastly, a large hypermethylated region overlapping the first FOXF1 exon was found in one of the ACD/MPV patients without a known pathogenic FOXF1 variation.

Conclusion

This is the first study providing genome wide methylation data on lung tissue of ACD/MPV patients. DNA methylation analyses in the FOXF1 locus excludes maternal imprinting of the 60 kb FOXF1 enhancer. Hypermethylation at the 60 kb FOXF1 enhancer might contribute to FOXF1 haploinsufficiency caused by heterozygous mutations in the FOXF1 coding region. Interestingly, DNA methylation analyses of patients without a genomic FOXF1 variant suggest that abnormal hypermethylation of exon 1 might play a role in some ACD/MPV in patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01134-1.

Perturbation of semaphorin and VEGF signaling in ACDMPV lungs due to FOXF1 deficiency

BACKGROUND

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal congenital lung disorder in neonates characterized by severe progressive respiratory failure and refractory pulmonary hypertension, resulting from underdevelopment of the peripheral pulmonary tree. Causative heterozygous single nucleotide variants (SNVs) or copy-number variant (CNV) deletions involving FOXF1 or its distant lung-specific enhancer on chromosome 16q24.1 have been identified in 80-90% of ACDMPV patients. FOXF1 maps closely to and regulates the oppositely oriented FENDRR, with which it also shares regulatory elements.

METHODS

To better understand the transcriptional networks downstream of FOXF1 that are relevant for lung organogenesis, using RNA-seq, we have examined lung transcriptomes in 12 histopathologically verified ACDMPV patients with or without pathogenic variants in the FOXF1 locus and analyzed gene expression profile in FENDRR-depleted fetal lung fibroblasts, IMR-90.

RESULTS

RNA-seq analyses in ACDMPV neonates revealed changes in the expression of several genes, including semaphorins (SEMAs), neuropilin 1 (NRP1), and plexins (PLXNs), essential for both epithelial branching and vascular patterning. In addition, we have found deregulation of the vascular endothelial growth factor (VEGF) signaling that also controls pulmonary vasculogenesis and a lung-specific endothelial gene TMEM100 known to be essential in vascular morphogenesis. Interestingly, we have observed a substantial difference in gene expression profiles between the ACDMPV samples with different types of FOXF1 defect. Moreover, partial overlap between transcriptome profiles of ACDMPV lungs with FOXF1 SNVs and FENDRR-depleted IMR-90 cells suggests contribution of FENDRR to ACDMPV etiology.

CONCLUSIONS

Our transcriptomic data imply potential crosstalk between several lung developmental pathways, including interactions between FOXF1-SHH and SEMA-NRP or VEGF/VEGFR2 signaling, and provide further insight into complexity of lung organogenesis in humans.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

FOXF1 as an Immunohistochemical Marker of Hilar Cholangiocarcinoma or Metastatic Pancreatic Ductal Adenocarcinoma. Single Institution Experience

Cholangiocarcinoma (CCA) is a liver malignancy associated with a poor prognosis. Its main subtypes are peripheral/intrahepatic and hilar/extrahepatic CCA. Several molecular, morphological and clinical similarities between hilar/extrahepatic CCA and pancreatic ductal adenocarcinoma (PDAC) have been described. FOXF1 is a transcription factor which has been described to have prognostic significance in various tumors and it is involved in the development of bile ducts. The aim of this study is to determine occurrence of nuclear expression of FOXF1 in both subtypes of CCA and metastatic PDAC and assess its potential usefulness as a diagnostic marker. Secondary aims were to investigate the use of C-reactive protein (CRP) immunohistochemistry for diagnosing intrahepatic peripheral CCA and the significance of histological features in CCA subtypes. 32 archive specimens of CCA, combined hepatocellular carcinoma-CCA (HCC-CCA) and liver metastasis of PDAC were stained by FOXF1 and CRP immunohistochemistry and evaluated to determine histological pattern. The CCAs were classified radiologically into peripheral/intrahepatic and hilar subtype. Using Fisher exact test, we identified nuclear FOXF1 as a fairly specific (87%) but insensitive (65%) marker of hilar and extrahepatic CCA and metastatic PDAC (p = 0.005). CRP immunohistochemistry was characterized by a high sensitivity and specificity, of 79% and 88%, respectively (p = 0.001). We did not identify any histomorphological features associated with either types of CCA or metastatic PDAC. As a conclusion of novel finding, FOXF1 immunohistochemistry may be regarded as a specific but insensitive marker of hilar/extrahepatic CCA and metastatic PDAC and it may help distinguish them from peripheral CCA.

Lung-specific distant enhancer cis regulates expression of FOXF1 and lncRNA FENDRR

The FOXF1 gene, causative for a neonatal lethal lung developmental disorder alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), maps 1.7 kb away from the long noncoding RNA gene FENDRR on the opposite strand, suggesting they may be coregulated. Using RNA sequencing in lung tissue from ACDMPV patients with heterozygous deletions of the FOXF1 distant enhancer located 286 kb upstream, leaving FOXF1 and FENDRR intact, we have found that the FENDRR and FOXF1 expressions were reduced by approximately 75% and 50%, respectively, and were monoallelic from the intact chromosome 16q24.1. In contrast, ACDMPV patients with FOXF1 SNVs had biallelic FENDRR expression reduced by 66%-82%. Corroboratively, depletion of FOXF1 by small interfering RNA in lung fibroblasts resulted in a 50% decrease of FENDRR expression. These data indicate that FENDRR expression in the lungs is regulated both in cis by the FOXF1 distant enhancer and in trans by FOXF1. Our findings are compatible with the involvement of FENDRR in FOXF1-related disorders, including ACDMPV.

Incidence of alveolar capillary dysplasia with misalignment of pulmonary veins in infants with unexplained severe pulmonary hypertension: The roles of clinical, pathological, and genetic testing

BACKGROUND

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare and fatal disorder that occurs in the developing fetal lungs; at birth, infants exhibit an oxygenation disorder accompanied by severe pulmonary hypertension (PH) and have a very short life span. ACDMPV is definitively diagnosed by pathological findings, and infants born with unexplained severe PH may not be properly diagnosed without a biopsy or autopsy.

METHODS

Japanese infants with unexplained severe PH were enrolled in this study. Genetic analyses were performed on DNA extracted from peripheral blood leukocytes. Sanger sequencing or next-generation sequencing was performed by coding exons and introns for FOXF1 in all samples. For individuals without pathogenic exonic variants, multiplex ligation-dependent probe amplification was performed to identify copy number variations (CNVs) in exons, introns, and in the upstream region of FOXF1.

RESULTS

This study included 30 infants who were diagnosed over the course of nine years. Four individuals had the pathogenic variations on the exon 1 of FOXF1, including two frameshift and two missense variations. Pathogenic CNVs were found in another five individuals.

CONCLUSION

In the pathologically proven ACDMPV patients, the ratios of cases with exonic variations, CNVs, and no genetic findings were reported as 45%, 45% and 10%, respectively. We estimate that about 30% (10 (9 + 1) out of 30) of individuals with unexplained severe PH had ACDMPV.

Alveolar capillary dysplasia without misalignment of pulmonary veins, hyperinflammation, megalocornea and overgrowth - Association with a homozygous 2bp-insertion in LTBP2?

We present a male infant with alveolar capillary dysplasia without misalignment of pulmonary veins, hyperinflammation, megalocornea and macrosomia/macrocephaly at birth. Whole-exome sequencing revealed a homozygous 2bp-insertion in the latent transforming growth factor-beta binding protein 2 (LTBP2) (c.278_279dup, p.(Ser94Glyfs*187)). So far, LTBP2-variants have been frequently reported with an eye-restricted phenotype including primary congenital glaucoma and megalocornea/microspherphakia and ectopia lentis with/without secondary glaucoma. Hitherto reported systemic phenotypes showed, among others, features as tall stature, finger anomalies, high-arched palate and cardiovascular anomalies. The main pathophysiological finding of our patient was an alveolar capillary dysplasia (with pulmonary arterial hypertension and right ventricular impairment but without misalignment of pulmonary veins) resulting in almost continuous oxygen demand and prolonged dependence on mechanical ventilation. He died of respiratory failure at the age of seven months. This patient may extend the LTBP2-related phenotype with resulting diagnostic implications.

Genetic Testing for Neonatal Respiratory Disease

Genetic mechanisms are now recognized as rare causes of neonatal lung disease. Genes potentially responsible for neonatal lung disease include those encoding proteins important in surfactant function and metabolism, transcription factors important in lung development, proteins involved in ciliary assembly and function, and various other structural and immune regulation genes. The phenotypes of infants with genetic causes of neonatal lung disease may have some features that are difficult to distinguish clinically from more common, reversible causes of lung disease, and from each other. Multigene panels are now available that can allow for a specific diagnosis, providing important information for treatment and prognosis. This review discusses genes in which abnormalities are known to cause neonatal lung disease and their associated phenotypes, and advantages and limitations of genetic testing.

Fast detection of FOXF1 variants in patients with alveolar capillary dysplasia with misalignment of pulmonary veins using targeted sequencing

BACKGROUND

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a lethal congenital lung disorder associated with heterozygous variants in the FOXF1 gene or its regulatory region. Patients with ACD/MPV unnecessarily undergo invasive and expensive treatments while awaiting a diagnosis. The aim of this study was to reduce the time to diagnose ACD/MPV by developing a targeted next-generation sequencing (NGS) panel that detects FOXF1 variants.

METHODS

A FOXF1-targeted NGS panel was developed for detection of mutations and large genomic alterations and used for retrospective testing of ACD/MPV patients and controls. Results were confirmed with Sanger sequencing and SNP array analysis.

RESULTS

Each amplicon of the FOXF1-targeted NGS panel was efficiently sequenced using DNA isolated from blood or cell lines of 15 ACD/MPV patients and 8 controls. Moreover, testing of ACD/MPV patients revealed six novel and six previously described pathogenic or likely pathogenic FOXF1 alterations.

CONCLUSION

We successfully designed a fast and reliable targeted genetic test to detect variants in the FOXF1 gene and its regulatory region in one run. This relatively noninvasive test potentially prevents unnecessary suffering for patients and reduces the use of futile and expensive treatments like extra-corporeal membrane oxygenation.

IMPACT

FOXF1-targeted NGS potentially prevents ACD/MPV patients from unnecessary suffering and expensive treatments. FOXF1-targeted NGS potentially reduces the number of misdiagnosis in ACD/MPV patients. Retrospective testing of ACD/MPV patients using FOXF1-targeted NGS revealed six novel pathogenic or likely pathogenic variants.

Potential interactions between the TBX4-FGF10 and SHH-FOXF1 signaling during human lung development revealed using ChIP-seq

Background

The epithelial-mesenchymal signaling involving SHH-FOXF1, TBX4-FGF10, and TBX2 pathways is an essential transcriptional network operating during early lung organogenesis. However, precise regulatory interactions between different genes and proteins in this pathway are incompletely understood.

Methods

To identify TBX2 and TBX4 genome-wide binding sites, we performed chromatin immunoprecipitation followed by next-generation sequencing (ChIP-seq) in human fetal lung fibroblasts IMR-90.

Results

We identified 14,322 and 1,862 sites strongly-enriched for binding of TBX2 and TBX4, respectively, 43.95% and 18.79% of which are located in the gene promoter regions. Gene Ontology, pathway enrichment, and DNA binding motif analyses revealed a number of overrepresented cues and transcription factor binding motifs relevant for lung branching that can be transcriptionally regulated by TBX2 and/or TBX4. In addition, TBX2 and TBX4 binding sites were found enriched around and within FOXF1 and its antisense long noncoding RNA FENDRR, indicating that the TBX4-FGF10 cascade may directly interact with the SHH-FOXF1 signaling.

Conclusions

We highlight the complexity of transcriptional network driven by TBX2 and TBX4 and show that disruption of this crosstalk during morphogenesis can play a substantial role in etiology of lung developmental disorders.

miR-574-5p Targets FOXN3 to Regulate the Invasion of Nasopharyngeal Carcinoma Cells via Wnt/β-Catenin Pathway

MicroRNAs (miR) are a class of non-coding endogenous RNA molecules that suppress the translation of protein-coding genes by destabilizing target mRNAs. The MiR-574-5p has been reported to be involved in the several types of cancer. However, the expression of miR-574-5p and its mechanism in nasopharyngeal carcinoma (NPC) remain unclear. We found that the expression level of miR-574-5p was significantly increased in the NPC cell lines. We further demonstrated that Forkhead box N3 (FOXN3) was a target gene of miR-574-5p. FOXN3 overexpression and inhibition reversed the promoting or suppressing effect, respectively, of NPC cell proliferation, migration and invasion caused by miR-574-5p. Furthermore, miR-574-5p enhanced the β-catenin and TCF4 protein expression by repressing FOXN3 expression, resulting in the activation of the Wnt/β-catenin signaling pathway, but the activity of the Wnt/β-catenin signaling pathway was inhibited by a miR-574-5p inhibitor or FOXN3 overexpression, which reversed the effect of miR-574-5p. Wound-healing and Transwell assays also showed that miR-574-5p promotes the cell migration and invasion of NPC cells, whereas the promoting effect of miR-574-5p was also reversed by a miR-574-5p inhibitor or FOXN3 overexpression. Collectively, these data suggested that miR-574-5p promotes NPC cell proliferation, migration, and invasion at least partly by targeting the FOXN3/Wnt/β-Catenin signaling pathway.

Interstitial lung disease in infancy

There is a wide differential diagnosis of early onset respiratory distress especially in term babies, and interstitial lung disease (chILD) is a rare but important consideration in this context. chILD manifesting immediately after birth is usually related to mutations in surfactant protein genes, or conditions related to the Congenital Acinar Dysplasia -Alveolar capillary dysplasia - Congenital Alveolar Dysplasia (CAD-ACD) spectrum. There is currently no specific treatment for these conditions, and management is supportive. Prognosis is very poor in most of these babies if onset is early, with relentless respiratory deterioration unless transplanted. Ideally, the diagnosis is made on genetic analysis, but this may be time-consuming and complex in CAD-ACD spectrum, so lung biopsy may be needed to avoid prolonged and futile treatment being instituted. Milder forms with prolonged survival have been reported. Early onset, less severe chILD is usually related to neuroendocrine cell hyperplasia of infancy (NEHI), pulmonary interstitial glycogenosis (PIG) and less severe disorders of surfactant proteins. PIG and NEHI are not specific entities, but are pulmonary dysmaturity syndromes, and there may be a number of underlying genetic and other cause. If the child is stable and thriving, many will not be subject to lung biopsy, and slow improvement and weaning of supplemental oxygen can be anticipated. Where possible, a precise genetic diagnosis should be made in early onset cHILD allow for genetic counselling. chILD survivors and their families have complex respiratory and other needs, and co-ordinated, multi-disciplinary support in the community is essential.

Histopathologic features of alveolar capillary dysplasia with misalignment of pulmonary veins with atypical clinical presentation

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare neonatal lung disease with fatal outcome. Typically, respiratory symptoms present in the first 24 hours of life and patients die within the neonatal period. Atypical, delayed clinical presentations and/or longer survival have also been reported. Here, we studied the clinicopathologic relationship of ACD/MPV by examining 16 cases of ACD/MPV, focusing on atypical features. Based on the presence of diffuse vs. focal/patchy ACD/MPV histopathologic changes, we divided the cases into classic and nonclassic pathology groups. MPV was found in all ACD/MPV. Ten of 16 cases exhibited classic diffuse abnormalities, while 6 of 16 had a nonclassic focal/patchy distribution. However, among 7 patients with atypical clinical features, only 2 had nonclassic pathology, while 4 out of 9 clinically typical cases had nonclassic ACD/MPV pathology. Marked intrapulmonary aberrant arteriovenous vessels were present in all atypical cases. In conclusion, clinical presentation is not always correlated with histopathology in ACD/MPV. Atypical ACD/MPV should be suspected in any infants with fulminant pulmonary hypertension. Abnormal pulmonary veins and aberrant intraseptal vessels are the most important clues for diagnosis. Additional studies are needed for further elucidation of diagnostic histological criteria of atypical ACD/MPV and to explore its pathogenesis.

Phenotypic and genetic spectrum of alveolar capillary dysplasia: a retrospective cohort study

OBJECTIVE

Alveolar capillary dysplasia (ACD) is one of the causes of pulmonary hypertension. Its diagnosis is histological but new pathogenetic data have emerged. The aim of this study was to describe a French cohort of patients with ACD to improve the comprehension and the diagnosis of this pathology which is probably underdiagnosed.

METHODS

A retrospective observational study was conducted in French hospitals. Patients born between 2005 and 2017, whose biological samples were sent to the French genetic reference centres, were included. Clinical, histological and genetic data were retrospectively collected.

RESULTS

We presented a series of 21 patients. The mean of postmenstrual age at birth was 37.6 weeks. The first symptoms appeared on the median of 2.5 hours. Pulmonary hypertension was diagnosed in 20 patients out of 21. Two cases had prolonged survival (3.3 and 14 months). Histological analysis was done on lung tissue from autopsy (57.1% of cases) or from percutaneous biopsy (28.6%). FOXF1 was found abnormal in 15 patients (71.4%): 8 deletions and 7 point mutations. Two deletions were found by chromosomal microarray.

CONCLUSION

This study is one of the largest clinically described series in literature. It seems crucial to integrate genetics early into diagnostic support. We propose a diagnostic algorithm for helping medical teams to improve diagnosis of this pathology.

Genotype-phenotype correlation in two Polish neonates with alveolar capillary dysplasia

BACKGROUND

Alveolar capillary dysplasia (ACD) is a rare cause of severe pulmonary hypertension and respiratory failure in neonates. The onset of ACD is usually preceded by a short asymptomatic period. The condition is refractory to all available therapies as it irreversibly affects development of the capillary bed in the lungs. The diagnosis of ACD is based on histopathological evaluation of lung biopsy or autopsy tissue or genetic testing of FOXF1 on chromosome 16q24.1. Here, we describe the first two Polish patients with ACD confirmed by histopathological and genetic examination.

CASE PRESENTATION

The patients were term neonates with high Apgar scores in the first minutes of life. They both were diagnosed prenatally with heart defects. Additionally, the first patient presented with omphalocele. The neonate slightly deteriorated around 12th hour of life, but underwent surgical repair of omphalocele followed by mechanical ventilation. Due to further deterioration, therapy included inhaled nitric oxide (iNO), inotropes and surfactant administration. The second patient was treated with prostaglandin E1 since birth due to suspicion of aortic coarctation (CoA). After ruling out CoA in the 3rd day of life, infusion of prostaglandin E1 was discountinued and immediately patient's condition worsened. Subsequent treatment included re-administration of prostaglandin E1, iNO and mechanical ventilation. Both patients presented with transient improvement after application of iNO, but died despite maximized therapy. They were histopathologically diagnosed post-mortem with ACD. Array comparative genomic hybridization in patient one and patient two revealed copy-number variant (CNV) deletions, respectively, ~ 1.45 Mb in size involving FOXF1 and an ~ 0.7 Mb in size involving FOXF1 enhancer and leaving FOXF1 intact.

CONCLUSIONS

Both patients presented with a distinct course of ACD, extra-pulmonary manifestations and response to medications. Surgery and ceasing of prostaglandin E1 infusion should be considered as potential causes of this variability. We further highlight the necessity of thorough genetic testing and histopathological examination and propose immunostaining for CD31 and CD34 to facilitate the diagnostic process for better management of infants with ACD.

Successful Management of an Infant with Atypical Presentation of Alveolar Capillary Dysplasia with Misalignment of the Pulmonary Veins

A newborn infant patient presented with persistent pulmonary hypertension. For right ventricular decompression, the ductus arteriosus was kept open by prostaglandin E ₁ infusion and was stented at the age of 4 weeks during heart catheterization. The child was weaned from mechanical ventilation, since pulmonary functions were adequate. A small atrial septal defect was identified and closed in cardiac catheterization laboratory to decrease preductal hypoxemia. Diagnostic workup led to the diagnosis of alveolar capillary dysplasia with misalignment of the pulmonary veins. Suprasystemic pulmonary arterial hypertension with persisting nitric oxide dependency remained the leading symptoms. The child underwent bilateral lung transplantation at the age of 28 months. He is well at the age of 44 months.

A familial case of alveolar capillary dysplasia with misalignment of the pulmonary veins: the clinicopathological features and unusual glomeruloid endothelial proliferation

Background

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare disorder of pulmonary vascular abnormality with persistent pulmonary hypertension of the newborn. The symptom usually presents within hours after birth, leading to an early demise. Heterozygous de novo point mutations and genomic deletions of the FOXF1 (forkhead box F1) gene or its upstream enhancer have been identified in most patients with ACD/MPV. Most cases of ACD/MPV are sporadic; however, familial cases are also reported in 10% of patients.

Case presentation

We herein report a case of familial ACD/MPV that showed unusual glomeruloid proliferation of endothelial cells. In this family, three of the four siblings died within two to 3 days after birth because of persistent pulmonary hypertension and respiratory failure. Only the second child remains alive and healthy. An autopsy was performed for the third and fourth children, resulting in a diagnosis of ACD/MPV based on the characteristic features, including misalignment of smaller pulmonary veins and lymphangiectasis. In both of these children, glomeruloid endothelial proliferation of vessels was noted in the interlobular septa. The vessels were immunohistochemically positive for D2–40, CD31, Factor VIII, and ERG, suggestive of differentiation for both lymphatic and blood vessels.

Conclusions

Unusual glomeruloid endothelial proliferation was observed in a familial ACD/MPV case. This histologic feature has not been described previously in ACD/MPV or any other pulmonary disease. Although the histogenesis of this histologic feature is unclear, this finding may suggest that ACD/MPV is a compound vascular and lymphovascular system disorder that exhibits various histologic features.

ChILD: A Pictorial Review of Pulmonary Imaging Findings in Childhood Interstitial Lung Diseases

Childhood interstitial lung disease (chILD) is a group of lung disorders characterized by lung remodeling leading to abnormal gas exchange. ChILD is classified differently from adult interstitial lung disease and encompasses 2 broad categories: "disorders more prevalent in infancy" (<2 years) and "disorders not specific to infancy" (>2 years). High-resolution computed tomography can play an important role in the evaluation of chILD by narrowing the differential diagnosis and preventing unnecessary invasive procedures if typical imaging patterns are recognized. Thus, the pediatric radiologist should consider chILD in children with respiratory distress and identify the imaging patterns to suggest the diagnosis.

Clinical, Histopathological, and Molecular Diagnostics in Lethal Lung Developmental Disorders

Lethal lung developmental disorders are a rare but important group of pediatric diffuse lung diseases presenting with neonatal respiratory failure. On the basis of histopathological appearance at lung biopsy or autopsy, they have been termed: alveolar capillary dysplasia with misalignment of the pulmonary veins, acinar dysplasia, congenital alveolar dysplasia, and other unspecified primary pulmonary hypoplasias. However, the histopathological continuum in these lethal developmental disorders has made accurate diagnosis challenging, which has implications for recurrence risk. Over the past decade, genetic studies in infants with alveolar capillary dysplasia with misalignment of the pulmonary veins have revealed the causative role of the dosage-sensitive FOXF1 gene and its noncoding regulatory variants in the distant lung-specific enhancer at chromosome 16q24.1. In contrast, the molecular bases of acinar dysplasia and congenital alveolar dysplasia have remained poorly understood. Most recently, disruption of the TBX4-FGF10-FGFR2 epithelial-mesenchymal signaling pathway has been reported in patients with these lethal pulmonary dysplasias. Application of next-generation sequencing techniques, including exome sequencing and whole-genome sequencing, has demonstrated their complex compound inheritance. These data indicate that noncoding regulatory elements play a critical role in lung development in humans. We propose that for more precise lethal lung developmental disorder diagnosis, a diagnostic pathway including whole-genome sequencing should be implemented.