Alveolar capillary dysplasia. Report of a case of prolonged life without extracorporeal membrane oxygenation (ECMO) and review of the literature

Interstitial lung disease in the newborn

Although relatively rare, interstitial lung diseases may present with respiratory distress in the newborn period. Most commonly these include developmental and growth disorders, disorders of surfactant synthesis and homeostasis, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy. Although the diagnosis of these disorders is sometimes made based on clinical presentation and imaging, due to the significant overlap between disorders and phenotypic variability, lung biopsy or, increasingly genetic testing is needed for diagnosis. These diseases may result in significant morbidity and mortality. Effective medical treatment options are in some cases limited and/or invasive. The genetic basis for some of these disorders has been identified, and with increased utilization of exome and whole genome sequencing even before lung biopsy, further insights into their genetic etiologies should become available.

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.

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.

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.

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.

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.

Two autopsy cases of siblings with alveolar capillary dysplasia: clinical and post-mortem issues

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare but fatal lung disorder, which causes persistent pulmonary hypertension of the newborn (PPHN) and which is unresponsive to treatment. We report the case of two siblings, both of whom died a few hours after birth because of severe pulmonary failure. Post-mortem histology confirmed ACD/MPV as the cause of death in both cases, and genetic analysis identified the same 16p13.3 deletion. ACD/MPV can occur suddenly in apparently healthy newborns after a regular pregnancy, and always leads to death. Nevertheless, an autopsy is not always performed after the death of an infant. For these reasons ACD/MPV represents a challenge for diagnosis and therapeutic management with medicolegal implications. Prenatal assessment of ACD/MPV is very difficult, and it should be suspected when irreversible and persistent fetal circulation occurs rapidly in newborns. An early diagnosis during pregnancy would facilitate adequate counselling regarding treatment and prognosis. When death occurs, a complete autopsy with histological and genetic investigations is recommended in order to define the exact cause of death, and potentially inform appropriate genetic counselling of family members who could be affected by hereditary disorders.

Early onset children's interstitial lung diseases: Discrete entities or manifestations of pulmonary dysmaturity?

Interstitial lung diseases in children (chILD) are rare and diverse. The current classifications include a group of early onset chILD specific to infancy, namely neuro-endocrine cell hyperplasia of infancy (NEHI), pulmonary interstitial glycogenosis (PIG) and the alveolar capillary-congenital acinar dysplasia (ACD-CAD) spectrum, as well as alveolar growth disorders. NEHI and PIG cells are seen in the normal developing foetal lung. We hypothesise that these conditions are in fact overlapping manifestations of pulmonary dysmaturity, respectively of airway, mesenchymal and vascular elements, rather than discrete clinical conditions in their own right. Clinically, these present as respiratory distress in early life. Mild cases rightly never undergo lung biopsy, and for these the clinical description 'persistent tachypnoea of infancy' has been proposed. In terms of pathology, we reviewed current literature, which showed that NEHI cells decline with age, and are not specific to NEHI, which we confirmed by unpublished re-analysis of a second dataset. Furthermore, specific genetic disorders which affect pulmonary maturation lead to a histological picture indistinguishable from NEHI. PIG and ACD-CAD are also associated with pulmonary growth disorders, and manifestations of PIG and NEHI may be present in the same child. We conclude that, contrary to current classifications, NEHI, PIG, and ACD-CAD should be considered as overlapping manifestations of pulmonary dysmaturation, frequently associated with disorders of alveolar growth, rather than as separate conditions. Identification of one of these patterns should be the start, not the end of the diagnostic journey, and underlying in particular genetic causes should be sought.

Alveolar capillary dysplasia with left heart obstruction - rare but lethal

Alveolar capillary dysplasia (ACD) is a rare neonatal lung disease characterized anatomically by a defective and hypoplastic development of pulmonary alveoli leading to persistent pulmonary hypertension (PPHN) and finally lethal respiratory failure. It is often associated with congenital left heart obstruction. Given the fatal prognosis an early diagnosis is important. However, due to the fast onset of PPHN in neonates and lack of pathognomonic signs for its cause, safe and fast detection of ACD is challenging. Therefore, following the exclusion of cardiac and common pulmonary causes, lung biopsy becomes essential for diagnosis.We hereby report a case of ACD with atrial septal defect type one and hypoplastic aortic arch with an ante-mortem diagnosis and discuss the current state of medicine in relation to ACD.

Alveolar capillary dysplasia with misalignment of the pulmonary veins: clinical, histological, and genetic aspects

Alveolar capillary dysplasia with misalignment of the pulmonary veins (ACD/MPV) is a rare and lethal disorder mainly involving the vascular development of the lungs. Since its first description, significant achievements in research have led to a better understanding of the underlying molecular mechanism of ACD/MPV and genetic studies have identified associations with genomic alterations in the locus of the transcription factor FOXF1. This in turn has increased the awareness among clinicians resulting in over 200 cases reported so far, including genotyping of patients in most recent reports. Collectively, this promoted a better stratification of the patient group, leading to new perspectives in research on the pathogenesis. Here, we provide an overview of the clinical aspects of ACD/MPV, including guidance for clinicians, and review the ongoing research into the complex molecular mechanism causing this severe lung disorder.

Neonatal Lung Disorders: Pattern Recognition Approach to Diagnosis

OBJECTIVE

Lung disease is a common indication for neonates to require medical attention, and neonatal chest radiographs are among the most common studies interpreted by pediatric radiologists. Radiographic features of many neonatal lung disorders overlap, and it may be difficult to differentiate among conditions.

CONCLUSION

This review presents an up-to-date practical approach to the radiologic diagnosis of neonatal lung disorders, with a focus on pattern recognition and consideration of clinical history, patient age, and symptoms.

Antenatal gastrointestinal anomalies in neonates subsequently found to have alveolar capillary dysplasia

Alveolar capillary dysplasia (ACD) is a rare condition with variable presentation and clinical course. Clinicians should consider this diagnosis in neonates presenting with nonlethal congenital gastrointestinal malformation, a period of well-being after birth then unremitting hypoxemia and refractory pulmonary hypertension. Lung biopsy and FOXF1 gene testing may help in diagnosis.

Pre-cannulation lung biopsy shortens ECMO course

We describe the clinical course of an infant with respiratory failure who underwent lung biopsy prior to cannulation for undergoing extracorporeal membrane oxygenation (ECMO). Pathology revealed alveolar capillary dysplasia, and ECMO was discontinued. Rapid diagnosis allowed for closure and saved resources. We recommend considering early biopsy in infants with atypical pulmonary hypertension.

Alveolar Capillary Dysplasia with Congenital Misalignment of Pulmonary Vessels

Alveolar capillary dysplasia with misalignment of pulmonary vessels is an uncommon congenital cause of persistent pulmonary hypertension of the newborn. It is universally fatal, and diagnosis is entirely dependent upon surgical lung biopsy. We present a case of alveolar capillary dysplasia with misalignment of pulmonary vessels occurring in a full-term neonate, emphasizing that early involvement of the thoracic surgeon for a histological diagnosis allows expensive and ineffective treatments to be avoided.

Genomic and Epigenetic Complexity of the FOXF1 Locus in 16q24.1: Implications for Development and Disease

The FOXF1 (Forkhead box F1) gene, located on chromosome 16q24.1 encodes a member of the FOX family of transcription factors characterized by a distinct forkhead DNA binding domain. FOXF1 plays an important role in epithelium-mesenchyme signaling, as a downstream target of Sonic hedgehog pathway. Heterozygous point mutations and genomic deletions involving FOXF1 have been reported in newborns with a lethal lung developmental disorder, Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins (ACDMPV). In addition, genomic deletions upstream to FOXF1 identified in ACDMPV patients have revealed that FOXF1 expression is tightly regulated by distal tissue-specific enhancers. Interestingly, FOXF1 has been found to be incompletely paternally imprinted in human lungs; characterized genomic deletions arose de novo exclusively on maternal chromosome 16, with most of them being Alu-Alu mediated. Regulation of FOXF1 expression likely utilizes a combination of chromosomal looping, differential methylation of an upstream CpG island overlapping GLI transcription factor binding sites, and the function of lung-specific long non-coding RNAs (lncRNAs). FOXF1 knock-out mouse models demonstrated its critical role in mesoderm differentiation and in the development of pulmonary vasculature. Additionally, epigenetic inactivation of FOXF1 has been reported in breast and colorectal cancers, whereas overexpression of FOXF1 has been associated with a number of other human cancers, e.g. medulloblastoma and rhabdomyosarcoma. Constitutional duplications of FOXF1 have recently been reported in congenital intestinal malformations. Thus, understanding the genomic and epigenetic complexity at the FOXF1 locus will improve diagnosis, prognosis, and treatment of ACDMPV and other human disorders associated with FOXF1 alterations.

Comparative analyses of lung transcriptomes in patients with alveolar capillary dysplasia with misalignment of pulmonary veins and in foxf1 heterozygous knockout mice

Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins (ACDMPV) is a developmental disorder of the lungs, primarily affecting their vasculature. FOXF1 haploinsufficiency due to heterozygous genomic deletions and point mutations have been reported in most patients with ACDMPV. The majority of mice with heterozygous loss-of-function of Foxf1 exhibit neonatal lethality with evidence of pulmonary hemorrhage in some of them. By comparing transcriptomes of human ACDMPV lungs with control lungs using expression arrays, we found that several genes and pathways involved in lung development, angiogenesis, and in pulmonary hypertension development, were deregulated. Similar transcriptional changes were found in lungs of the postnatal day 0.5 Foxf1^+/− mice when compared to their wildtype littermate controls; 14 genes, COL15A1, COL18A1, COL6A2, ESM1, FSCN1, GRINA, IGFBP3, IL1B, MALL, NOS3, RASL11B, MATN2, PRKCDBP, and SIRPA, were found common to both ACDMPV and Foxf1 heterozygous lungs. Our results advance knowledge toward understanding of the molecular mechanism of ACDMPV, lung development, and its vasculature pathology. These data may also be useful for understanding etiologies of other lung disorders, e.g. pulmonary hypertension, bronchopulmonary dysplasia, or cancer.

Novel FOXF1 mutations in sporadic and familial cases of alveolar capillary dysplasia with misaligned pulmonary veins imply a role for its DNA binding domain

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare and lethal developmental disorder of the lung defined by a constellation of characteristic histopathological features. Nonpulmonary anomalies involving organs of gastrointestinal, cardiovascular, and genitourinary systems have been identified in approximately 80% of patients with ACD/MPV. We have collected DNA and pathological samples from more than 90 infants with ACD/MPV and their family members. Since the publication of our initial report of four point mutations and 10 deletions, we have identified an additional 38 novel nonsynonymous mutations of FOXF1 (nine nonsense, seven frameshift, one inframe deletion, 20 missense, and one no stop). This report represents an up to date list of all known FOXF1 mutations to the best of our knowledge. Majority of the cases are sporadic. We report four familial cases of which three show maternal inheritance, consistent with paternal imprinting of the gene. Twenty five mutations (60%) are located within the putative DNA-binding domain, indicating its plausible role in FOXF1 function. Five mutations map to the second exon. We identified two additional genic and eight genomic deletions upstream to FOXF1. These results corroborate and extend our previous observations and further establish involvement of FOXF1 in ACD/MPV and lung organogenesis.

Alveolar capillary dysplasia with misalignment of pulmonary [corrected] veins: concordance between pathological and molecular diagnosis

We report the case of a newborn with alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV), a rare condition of unknown etiology presenting in the neonatal period with significant persistent pulmonary hypertension. The diagnosis was made by lung biopsy and confirmed at autopsy. Specific genetic analysis demonstrated defects in the FOXF1 gene. The diagnosis of ACD/MPV requires a high level of suspicion and is made by lung biopsy or necropsy examination by a pediatric pathologist with experience in this condition. The availability of genetic testing has led to increasing diagnosis of patients with this lethal disorder and can influence their management, specifically by indicating the need for lung biopsy in a critically ill newborn.

Long survival of congenital alveolar capillary dysplasia patient with NO inhalation and epoprostenol: effect of sildenafil, beraprost and bosentan

The case is described herein of a patient with alveolar capillary dysplasia with double-outlet right ventricle and duodenal atresia who survived for a remarkably long time. The newborn girl was born at a gestational age of 36 weeks and weighed 1926 g. One min after delivery the Apgar score was 4. The patient had persistent pulmonary hypertension (PH) and needed nitric oxide inhalation and i.v. epoprostenol all through her life. Although other oral medications for PH were tried, they could not be used in practice because of gastrointestinal complications. The patient died on the 237 th day of life as a result of worsening PH associated with infection.

A familial case of alveolar capillary dysplasia with misalignment of pulmonary veins supports paternal imprinting of FOXF1 in human

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare developmental lung disorder that is uniformly lethal. Affected infants die within the first few weeks of their life despite aggressive treatment, although a few cases of late manifestation and longer survival have been reported. We have shown previously that mutations and deletions in FOXF1 are a cause of this disorder. Although most of the cases of ACD/MPV are sporadic, there have been infrequent reports of familial cases. We present a family with five out of six children affected with ACD/MPV. DNA analysis identified a missense mutation (c.416G>T; p.Arg139Leu) in the FOXF1 gene that segregated in the three affected siblings tested. The same variant is also present as a de novo mutation in the mother and arose on her paternally derived chromosome 16. The two tested affected siblings share the same chromosome 16 haplotype inherited from their maternal grandfather. Their single healthy sibling has a different chromosome 16 haplotype inherited from the maternal grandmother. The results are consistent with paternal imprinting of FOXF1 in human.

Increased NADPH oxidase-derived superoxide is involved in the neuronal cell death induced by hypoxia-ischemia in neonatal hippocampal slice cultures

Neonatal brain hypoxia-ischemia (HI) results in neuronal cell death. Previous studies indicate that reactive oxygen species, such as superoxide, play a key role in this process. However, the cellular sources have not been established. In this study we examine the role of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex in neonatal HI brain injury and elucidate its mechanism of activation. Rat hippocampal slices were exposed to oxygen glucose deprivation (OGD) to mimic the conditions seen in HI. Initial studies confirmed an important role for NADPH oxidase-derived superoxide in the oxidative stress associated with OGD. Further, the OGD-mediated increase in apoptotic cell death was inhibited by the NADPH oxidase inhibitor apocynin. The activation of NADPH oxidase was found to be dependent on the p38 mitogen-activated protein kinase-mediated phosphorylation and activation of the p47(phox) subunit. Using an adeno-associated virus antisense construct to selectively decrease p47(phox) expression in neurons showed that this led to inhibition of both the increase in superoxide and the neuronal cell death associated with OGD. We also found that NADPH oxidase inhibition in a neonatal rat model of HI or scavenging hydrogen peroxide reduced brain injury. Thus, we conclude that activation of the NADPH oxidase complex contributes to the oxidative stress during HI and that therapies targeted against this complex could provide neuroprotection against the brain injury associated with neonatal HI.

16q24.1 microdeletion in a premature newborn: usefulness of array-based comparative genomic hybridization in persistent pulmonary hypertension of the newborn

OBJECTIVE

Report of a 16q24.1 deletion in a premature newborn, demonstrating the usefulness of array-based comparative genomic hybridization in persistent pulmonary hypertension of the newborn and multiple congenital malformations.

DESIGN

Descriptive case report.

SETTING

Genetic department and neonatal intensive care unit of a tertiary care children's hospital.

INTERVENTIONS

None.

PATIENT

We report the case of a preterm male infant, born at 26 wks of gestation. A cardiac malformation and bilateral hydronephrosis were diagnosed at 19 wks of gestation. Karyotype analysis was normal, and a 22q11.2 microdeletion was excluded by fluorescence in situ hybridization analysis. A cesarean section was performed due to fetal distress. The patient developed persistent pulmonary hypertension unresponsive to mechanical ventilation and nitric oxide treatment and expired at 16 hrs of life.

MEASUREMENTS AND MAIN RESULTS

An autopsy revealed partial atrioventricular canal malformation and showed bilateral dilation of the renal pelvocaliceal system with bilateral ureteral stenosis and annular pancreas. Array-based comparative genomic hybridization analysis (Agilent oligoNT 44K, Agilent Technologies, Santa Clara, CA) showed an interstitial microdeletion encompassing the forkhead box gene cluster in 16q24.1. Review of the pulmonary microscopic examination showed the characteristic features of alveolar capillary dysplasia with misalignment of pulmonary veins. Some features were less prominent due to the gestational age.

CONCLUSIONS

Our review of the literature shows that alveolar capillary dysplasia with misalignment of pulmonary veins is rare but probably underreported. Prematurity is not a usual presentation, and histologic features are difficult to interpret. In our case, array-based comparative genomic hybridization revealed a 16q24.1 deletion, leading to the final diagnosis of alveolar capillary dysplasia with misalignment of pulmonary veins. It emphasizes the usefulness of array-based comparative genomic hybridization analysis as a diagnostic tool with implications for both prognosis and management decisions in newborns with refractory persistent pulmonary hypertension and multiple congenital malformations.

Misalignment of lung vessels and alveolar capillary dysplasia: a case report with autopsy

Misalignment of lung vessels (MLV) with or without alveolar capillary dysplasia (ACD) is a rare cause of idiopathic persistent pulmonary hypertension of the neonate. This report describes a full-term infant with severe and intractable pulmonary hypertension. The patient's condition progressively deteriorated despite high-frequency oscillatory ventilation, infusion of magnesium sulfate, dopamine, and dobutamine to control blood pressure, and nitric oxide inhalation therapy. The infant died at 5 days of age. The diagnosis of MLV with ACD was established by autopsy. Histopathologic analysis revealed a failure of formation and an ingrowth of alveolar capillaries, thickening of the alveolar walls, poor contact of capillaries with alveolar epithelium, small intra-acinar muscularized arterioles, and anomalous pulmonary veins within bronchovascular bundles. The low rate of diagnosis of MLV with or without ACD may be because of the early high mortality rate or patchy involvement in some cases. Increasing awareness of this clinical entity may prevent the use of costly, invasive, and probably ineffective procedures. Short-term improvement after inhalation of nitric oxide does not lead to long-term survival but merely provides time for potential lung transplantation.

Alveolar capillary dysplasia

Alveolar capillary dysplasia with misalignment of the pulmonary veins (ACD/MPV) is a rare, fatal developmental lung disorder of neonates and infants. This review aims to address recent findings in the etiology and genetics of ACD/MPV and to raise awareness of this poorly known disease, which may also present as milder, unclassified forms. Successively discussed are what is known about the epidemiology, pathogenesis, pathophysiology, diagnostic indicators and approaches, genetic testing, treatment, and cases of delayed onset. The review concludes with suggestions for future directions to answer the many unknowns about this disorder.

A novel association of alveolar capillary dysplasia, atypical duodenal atresia, and subglottic stenosis

Alveolar capillary dysplasia (ACD), which is a rare and lethal congenital pulmonary anomaly found in newborns, begins its onset or causes deterioration of the infant's condition some time after birth. Various congenital anomalies in combination with ACD have been reported, except for subglottic stenosis. Therefore, we aim to report a novel association in a case of ACD with the combination of atypical duodenal atresia and subglottic stenosis. The male infant was scheduled for duodeno-duodenostomy because a double-bubble sign was observed on a chest radiograph. He arrived at the operating theater without any symptoms. After induction of general anesthesia, although mask ventilation was performed without difficulties throughout the entire procedure, oxygen saturation values of the upper and lower extremities dissociated after several attempts of intubation. Surgery was canceled because of instability of the respiratory condition. Respiratory insufficiency worsened progressively, and the infant died at 5 days of age. An autopsy confirmed ACD and revealed cartilaginous subglottic stenosis, which had made intubation difficult. This report highlights the hazards of the onset and worsening of ACD, and the importance of thorough echocardiography before surgery when atypical duodenal atresia is suspected. Anesthesiologists should also be prepared for the difficulty of intubation.

New Entities and Diagnostic Challenges in Pediatric Lung Disease

The differential diagnosis of diffuse lung disease in children differs considerably from adults, and analysis of pediatric lung biopsies may prove challenging for pathologists with more extensive exposure to adult lung biopsies. Biopsy diagnosis of pediatric lung disease continues to evolve as new pathologic entities are recognized and new genetic determinants of disease are discovered. This article describes the clinical characteristics, pathologic features, and differential diagnosis of challenging and recently described entities in pediatric lung disease. The specific entities discussed include alveolar capillary dysplasia, genetic disorders of surfactant metabolism, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy.

Expression of angiogenic and vasculogenic proteins in the lung in alveolar capillary dysplasia/misalignment of pulmonary veins: an immunohistochemical study

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare, universally fatal developmental disorder of the lung affecting both the parenchyma and the vasculature. Its cause remains incompletely understood; the occurrence of familial cases has suggested a genetic abnormality. While several candidate genes have been studied previously, the affected pathway(s) have not yet been fully defined. The expression patterns of 8 gene products (endothelial nitric oxide synthase-3, fetal liver kinase-1, hypoxia inducible factor 1α, Von Hippel Lindau protein, 3 vascular endothelial growth factors [VEGF147, VEGFC1, and VEGFA20], and activin receptor-like kinase 1), all known to have a role in vascular development in the lung, were studied in 13 ACD/MPV and 17 control lungs by immunohistochemistry to further address the underlying molecular abnormality. Expression was graded with regard to degree and extent for multiple components of the lung parenchyma and pulmonary vasculature for each antibody. Statistical analyses of the data using the Mann-Whitney test revealed only a few significant differences (P ≤ 0.05) in degree of expression between ACD/MPV and control lung samples and do not clearly implicate one of these genes in ACD/MPV.

Misplaced pulmonary arteries in an adult patient with pulmonary hypertension

Misalignment of pulmonary vessels, with or without alveolar capillary dysplasia, is a rare cause of persistent pulmonary hypertension in the newborn. The prognosis is poor, with virtually all patients succumbing to unremitting hypoxaemic respiratory failure and death during the newborn period. We report the CT and histological findings of misplaced pulmonary arteries in a previously healthy young adult patient who presented with pulmonary arterial hypertension. Contiguous high-resolution spiral CT angiography showed small pulmonary arteries coursing within the interlobular septa and enlarged central pulmonary arteries. Surgical lung biopsy demonstrated anomalous muscularised pulmonary arteries in the interlobular septa. This is, to our knowledge, the first report of misplaced pulmonary arteries presenting in an adult patient and may represent a forme fruste of the neonatal vascular anomaly. A possible association with pulmonary arterial hypertension is also suggested in this case.

Genetic Basis of Children's Interstitial Lung Disease

Specific genetic causes for children's interstitial lung disease (chILD) have been identified within the past decade. These include deletions of or mutations in genes encoding proteins important in surfactant production and function (SP-B, SP-C, and ABCA3), surfactant catabolism (GM-CSF receptor), as well as transcription factors important for surfactant production (TTF1) or lung development (Fox F1), with heterozygous deletions or loss-of-function mutations of the latter resulting in alveolar capillary dysplasia (ACD) with misalignment of the pulmonary veins. Familial pulmonary fibrosis in adults may result from mutations in genes encoding components of telomerase and SP-A2. While not yet reported in children, the expression of these genes in alveolar type II epithelial cells supports a key role for the disruption of normal homeostasis in this cell type in the pathogenesis of interstitial lung disease. The identification of specific genetic causes for chILD now allows for the possibility of non-invasive diagnosis, and provides insight into basic cellular mechanisms that may allow the development of novel therapies.

Diagnostic Pathology of Diffuse Lung Disease in Children

The pathologic classification of diffuse lung disease in children and adolescents has undergone revision in recent years in response to rapid developments and new discoveries in the field. A number of important advancements have been made in the last 10 years including the description of new genetic mutations causing severe lung disease in infants and children, as well as the description of new pathologic entities in infants. These recently described entities, including ABCA3 surfactant disorders, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy, are being recognized with increasing frequency. This review will include brief discussion of the etiology and pathogenesis of the major groups of diffuse lung disease in children. Histopathologic features are discussed for each of the major categories of diffuse lung disease in children, beginning with the genetic, developmental, and alveolar growth disorders common in infancy, followed by brief discussion of airway diseases, immunologic diseases, and pulmonary vascular diseases seen more commonly in older children. A protocol for handling pediatric wedge lung biopsies is also discussed, which optimizes the diagnostic yield of lung biopsies in this population.

Diffuse lung disease in infancy: a proposed classification applied to 259 diagnostic biopsies

Thoracoscopic and open lung biopsies are being performed with increasing frequency in neonates and infants and are an important component of the diagnostic evaluation of respiratory compromise in these very young children. Diffuse lung disease in infancy includes a wide spectrum of developmental, genetic, inflammatory, infectious, and reactive disorders. The majority of the entities diagnosed in infancy (68%) in this retrospective lung biopsy series are seen almost exclusively in this age group and not in older children and adults. These include primary disorders of pulmonary and pulmonary vascular development, secondary disorders affecting prenatal and/or postnatal lung growth, genetic disorders of surfactant function, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy. Although the diagnostic approach to infant lung biopsies is guided primarily by the clinical history and imaging findings, all cases require careful assessment of alveolar growth, vascular architecture, interstitial cellularity, and histologic patterns associated with genetic abnormalities of surfactant metabolism. Recognition of one or more of these processes assists not only in treatment planning but also in further diagnostic evaluation and prognostication and may have implications for subsequent siblings and other family members. In this study, we have applied a classification system developed by a North American multicenter multidisciplinary group to lung biopsies seen at our institution and have used this material to describe and illustrate the spectrum of diffuse lung disease in infancy.

Genomic and genic deletions of the FOX gene cluster on 16q24.1 and inactivating mutations of FOXF1 cause alveolar capillary dysplasia and other malformations

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare, neonatally lethal developmental disorder of the lung with defining histologic abnormalities typically associated with multiple congenital anomalies (MCA). Using array CGH analysis, we have identified six overlapping microdeletions encompassing the FOX transcription factor gene cluster in chromosome 16q24.1q24.2 in patients with ACD/MPV and MCA. Subsequently, we have identified four different heterozygous mutations (frameshift, nonsense, and no-stop) in the candidate FOXF1 gene in unrelated patients with sporadic ACD/MPV and MCA. Custom-designed, high-resolution microarray analysis of additional ACD/MPV samples revealed one microdeletion harboring FOXF1 and two distinct microdeletions upstream of FOXF1, implicating a position effect. DNA sequence analysis revealed that in six of nine deletions, both breakpoints occurred in the portions of Alu elements showing eight to 43 base pairs of perfect microhomology, suggesting replication error Microhomology-Mediated Break-Induced Replication (MMBIR)/Fork Stalling and Template Switching (FoSTeS) as a mechanism of their formation. In contrast to the association of point mutations in FOXF1 with bowel malrotation, microdeletions of FOXF1 were associated with hypoplastic left heart syndrome and gastrointestinal atresias, probably due to haploinsufficiency for the neighboring FOXC2 and FOXL1 genes. These differences reveal the phenotypic consequences of gene alterations in cis.

Aortic coarctation associated with alveolar capillary dysplasia and misalignment of the pulmonary veins

After surgical repair of an aortic coarctation a term infant presented with severe pulmonary hypertension and cyanosis unresponsive to treatment including extracorporeal membrane oxygenation. The atypical clinical course became apparent once the accompanying diagnosis of congenital alveolar capillary dysplasia with misalignment of the pulmonary veins had been established at autopsy. In infants with congenital heart defects and with refractory pulmonary hypertension unexplainable on anatomic findings, a lung biopsy at the time of cardiac repair should be considered to avoid further therapies that would not alter the uniformly fatal course of this rare lung disorder.

Alveolar capillary dysplasia presenting as pneumothorax: a case report and review of literature

Alveolar capillary dysplasia, although rare, is a universally fatal form of persistent pulmonary hypertension of the newborn. We report a case of a newborn male baby who developed respiratory distress and pneumothorax 11 h after an uncomplicated delivery. He deteriorated despite full ventilatory support and extracorporeal membrane oxygenation (ECMO). Open lung biopsy provided a diagnosis of alveolar capillary dysplasia and decision was made to withdraw treatment.

Congenital alveolar capillary dysplasia and associated gastrointestinal anomalies

Congenital alveolar capillary dysplasia is a rare cause of irreversible pulmonary hypertension with 100% mortality. We present three cases of congenital alveolar capillary dysplasia with associated gastrointestinal abnormalities. Three full-term neonates presented with pulmonary hypertension needing ventilatory support by oscillation. Of the three, two neonates subsequently needed extracorporeal membrane oxygenation. Abdominal distension associated with bilious aspirates was the gastrointestinal manifestation. One child had duodenal atresia and anorectal anomaly, one with intestinal malrotation and the other with a rare combination of intestinal malrotaion and total colonic Hirschsprung's disease. All three infants succumbed to pulmonary hypertension at mean age 34 days. The etiopathogenesis and pathology of this condition are discussed with a comprehensive review of the literature.

Late presentation of alveolar capillary dysplasia in an infant

OBJECTIVE

To report a case of late presentation of alveolar capillary dysplasia and misalignment of pulmonary veins.

DESIGN

Descriptive case report.

SETTING

Pediatric intensive care unit of a tertiary care children's hospital.

PATIENT

Seven-week-old female infant with severe hypoxemic respiratory failure.

CONCLUSION

Alveolar capillary dysplasia with misalignment of pulmonary veins is a cause of primary pulmonary hypertension in newborns that can rarely present past the newborn period. Early lung biopsy can be helpful in establishing the diagnosis and avoiding ineffective, futile, and expensive therapeutic interventions.

Persistent pulmonary hypertension of newborn due to congenital capillary alveolar dysplasia

Congenital alveolar capillary dysplasia is a rare and fatal cause of pulmonary hypertension in neonates. We report on a term baby with severe pulmonary hypertension unresponsive to high-frequency ventilation and nitric oxide. A diagnosis of alveolar capillary dysplasia was established on autopsy. We review the literature regarding pathophysiology, clinical presentations, associated malformations, and treatment trials.

Distal angiogenesis: a new concept for lung vascular morphogenesis

Although several molecular players have been described that play a role during the early phases of lung development, it is still unknown how the vasculature develops in relation to the airways. Two opposing models describe development of lung vasculature: one suggests that both vasculogenesis and angiogenesis are involved, whereas the second describes vasculogenesis as the primary mechanism. Therefore, we examined the development of the murine pulmonary vasculature through a morphological analysis from the onset of lung development [9.5 days postcoital (dpc)] until the pseudoglandular stage (13.5 dpc). We analyzed fetal lungs of Tie2-LacZ transgenic mice as well as serial sections of wild-type lungs stained with endothelial-specific antibodies (Flk-1, Fli-1, and PECAM-1). Embryos were processed with intact blood circulation to maintain the integrity of the vasculature; hence individual vessels could be identified with accuracy through serial section analysis. Furthermore, circulating primitive erythrocytes, formed exclusively by the blood islands in the yolk sac, are trapped in vessels during fixation, which proves the connection with the embryonic circulation. We report that from the first morphological sign of lung development, a clear vascular network exists that is in contact with the embryonic circulation. We propose distal angiogenesis as a new concept for early pulmonary vascular morphogenesis. In this model, capillary networks surround the terminal buds and expand by formation of new capillaries from preexisting vessels as the lung bud grows. The fact that at an early embryonic stage a complete vascular network exists may be important for the general understanding of embryonic development.

Pulmonary pathology

Common causes of neonatal respiratory distress include meconium aspiration, pneumonia, persistent pulmonary hypertension of the newborn, pneumothorax and cystic adenomatoid malformation. Genomics and proteomics have enabled the recent recognition of several additional disorders that lead to neonatal death from respiratory disease. These are broadly classified as disorders of lung homeostasis and have pathological features of proteinosis, interstitial pneumonitis or lipidosis. These pathological changes result from inherited disorders of surfactant proteins or granulocyte-macrophage colony stimulating factor. Abnormal lung vascular development is the basis for another cause of fatal neonatal respiratory distress, alveolar capillary dysplasia with or without associated misalignment of veins. Diagnosis of these genetically transmitted disorders is important because of the serious implications for future siblings. There is also a critical need for establishing an archival tissue bank to permit future molecular biological studies.

Dysplasie alvéolo-capillaire avec défaut d’alignement des vaisseaux pulmonaires

Alveolar capillary dysplasia (ACD), with or without pulmonary vein misalignment is a uniformly fatal cause of persistent pulmonary hypertension and respiratory failure, first described in 1981. We report the case of ACD in a full term newborn with post mortem pathologic confirmation. Sixty five cases have been reported in the literature, most are sporadic, but a few cases of familial ACD suggest an autosomal recessive inheritance. In 55% of the reported cases of ACD other cardiovascular, digestive or urogenital anomalies were associated. ACD is presumed to be a primary capillary disorder. It affects full-term neonates who exhibit respiratory distress during the early post natal period due to pulmonary hypertension and die within 3 weeks of birth. Histologic findings include a decrease in the number of alveolar capillaries, which are placed centrally within the intralobular septa, ectatic veins accompany the bronchovascular bundles instead of being in their normal position in the interlobular septum, and muscularized pulmonary arteries extend to the distal level. Prognosis is very poor, intravenous prostacyclin with inhaled nitric oxide have been reported in the cases with the best survival.

Open lung biopsy in neonatal and paediatric patients referred for extracorporeal membrane oxygenation (ECMO)

BACKGROUND

This study was undertaken to determine the usefulness, safety, and most appropriate timing of open lung biopsy in infants and children considered for and on extracorporeal membrane oxygenation (ECMO) for respiratory failure.

METHODS

A retrospective review of children referred for consideration of and placed on ECMO in our institution in the period 1996-2002.

RESULTS

506 patients were referred, 15 (3%) of whom underwent antemortem open lung biopsy (eight neonatal, four paediatric, and three cardiac patients). In the neonatal group open lung biopsy contributed to clinical decision making in all patients. Four neonates had a fatal lung dysplasia (three alveolar capillary dysplasia and one surfactant protein B deficiency) and treatment was withdrawn. Of the other four neonates, two had pulmonary hypoplasia, one had pulmonary lymphangiectasia, and one had meconium aspiration with mild barotrauma. Treatment was continued in these four patients and two survived. In the paediatric group the biopsies were of clinical relevance in two infants with pertussis who had lung infarction on biopsy in whom treatment was withdrawn. In the other two paediatric patients the biopsies were equivocal, treatment was continued, but both patients died. In the cardiac group, who presented perioperatively with pulmonary hypertension, the biopsies excluded a fatal lung dysplasia and severe pulmonary vascular disease but all three infants died. One patient had non-fatal bleeding complications.

CONCLUSION

Open lung biopsy is clinically most useful when performed to diagnose fatal lung dysplasias in neonates and to confirm the presence of viable lung tissue in patients with acute lung injury due to pertussis infection.