Interstitial lung disease in infancy and early childhood: a clinicopathological primer

Bi-allelic LAMP3 variants in childhood interstitial lung disease: a surfactant-related disease

BACKGROUND

LAMP3 encodes a lysosomal membrane protein associated with lamellar bodies and has recently been proposed as a candidate gene for childhood interstitial lung diseases (chILD). Here, we identified two LAMP3 variants in a proband with chILD and performed functional validation of these variants as well as the previously reported variants to demonstrate the role of LAMP3 in pathology.

METHODS

LAMP3 variants were identified by exome sequencing. Ex vivo studies included mRNA analysis from nasal brushing and lung tissue and immunohistochemistry from lung biopsy. In vitro functional analyses in the A549 cell line included immunofluorescence staining and expression analysis of LAMP3. Interactions between LAMP3 and the surfactant protein (SP)-B and SP-C were evaluated by co-immunoprecipitation.

FINDINGS

Two heterozygous LAMP3 variants (Y302Qfs∗2 and T268M) were identified in a 15 year old boy with chILD. LAMP3 mRNA revealed that the frameshift variant resulted in nonsense-mediated mRNA decay. Reduced LAMP3 expression was confirmed in the patient's lung tissue. Functional studies of the T268M and the previously reported G288R variant revealed reduced levels of the mutant proteins. In addition, impaired N-glycosylation and protein instability were demonstrated with the T268M variant. Finally, we provided evidence for an interaction between LAMP3 and SP-B and SP-C, revealing a direct link between LAMP3 and surfactant metabolism.

INTERPRETATION

LAMP3 bi-allelic variants leading to LAMP3 dysfunction emerges as a cause of chILD associated with a heterogeneous phenotype that remains to be further defined. The close links between LAMP3 and surfactant metabolism could explain the pathophysiology of this genetic disease.

FUNDING

No specific funding.

Genetic underpinning of idiopathic pulmonary fibrosis: the role of mucin

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease characterized by progressive scarring and reduced survival. The development of IPF is influenced by rare and common genetic variants, cigarette smoking, aging, and environmental exposures. Among the two dozen genetic contributors, the MUC5B promoter variant (rs35705950) is the dominant risk factor, increasing the risk of both familial and sporadic IPF and accounting for nearly 50% of the genetic predisposition to the disease.

AREAS COVERED

This review provides an expert perspective on the genetic underpinnings of IPF rather than a systematic analysis, emphasizing key insights into its genetic basis. The articles referenced in this review were identified through targeted searches in PubMed, Scopus, and Web of Science for studies published between 2000 and 2023, prioritizing influential research on the genetic factors contributing to IPF. Search terms included 'idiopathic pulmonary fibrosis,' 'genetics,' 'MUC5B,' 'telomere dysfunction,' and 'surfactant proteins.' The selection of studies was guided by the authors' expertise, focusing on the most relevant publications.

EXPERT OPINION

The identification of genetic variants not only highlights the complexity of IPF but also offers potential for earlier diagnosis and personalized treatment strategies targeting specific genetic pathways, ultimately aiming to improve patient outcomes.

Pediatric Diffuse Lung Disease in Infants: Imaging Findings and Histopathologic Correlation

Childhood interstitial lung disease (chILD) encompasses a diverse group of genetic, infectious, and inflammatory conditions affecting infants and children. The recognition and understanding of these entities have highlighted the necessity for more accurate classification. This group of rare heterogeneous diseases comprises more than 200 different conditions and has a combined estimated prevalence of less than one patient per 100 000 children. Hence, a systematic diagnostic approach is crucial. This article describes a diagnostic approach for pediatric diffuse lung diseases in infancy, including an analysis of clinical presentations and imaging and histologic features to effectively distinguish among various chILD entities. Although they often have overlapping and nonspecific radiologic features, some chILD entities may exhibit typical imaging findings, resulting in a CT diagnosis or aiding in narrowing the differential diagnosis, thus guiding the clinician to the appropriate genetic tests, potentially limiting unnecessary biopsies. This approach aims to enhance the understanding and diagnosis of chILD in infants, thereby facilitating improved patient care.

An interdisciplinary consensus approach to pulmonary hypertension in developmental lung disease

It is increasingly recognised that diverse genetic respiratory disorders present as severe pulmonary hypertension (PH) in the neonate and young infant, but many controversies and uncertainties persist regarding optimal strategies for diagnosis and management to maximise long-term outcomes. To better define the nature of PH in the setting of developmental lung disease (DEVLD), in addition to the common diagnoses of bronchopulmonary dysplasia and congenital diaphragmatic hernia, we established a multidisciplinary group of expert clinicians from stakeholder paediatric specialties to highlight current challenges and recommendations for clinical approaches, as well as counselling and support of families. In this review, we characterise clinical features of infants with DEVLD/DEVLD-PH and identify decision-making challenges including genetic evaluations, the role of lung biopsies, the use of imaging modalities and treatment approaches. The importance of working with team members from multiple disciplines, enhancing communication and providing sufficient counselling services for families is emphasised to create an interdisciplinary consensus.

The Clinical Approach to Interstitial Lung Disease in Childhood: A Narrative Review Article

Interstitial lung disease (ILD) comprises a group of respiratory diseases affecting the interstitium of the lungs, which occur when a lung injury triggers an abnormal healing response, and an inflammatory process leads to altered diffusion and restrictive respiratory dysfunction. The term "interstitial" may be misleading, as other components of the lungs are usually also involved (epithelium, airways, endothelium, and so on). Pediatric conditions (childhood interstitial lung disease, chILD) are different from adult forms, as growing and developing lungs are affected and more diverse and less prevalent diseases are seen in childhood. Diffuse parenchymal lung disease (DPLD) and diffuse lung disease (DLD) can be used interchangeably with ILD. Known etiologies of chILD include chronic infections, bronchopulmonary dysplasia, aspiration, genetic mutations leading to surfactant dysfunction, and hypersensitivity pneumonitis due to drugs or environmental exposures. Many forms are seen in disorders with pulmonary involvement (connective tissue disorders, storage diseases, malignancies, and so on), but several conditions have unknown origins (desquamative pneumonitis, pulmonary interstitial glycogenosis, neuroendocrine cell hyperplasia in infancy, and so on). Currently, there is no consensus on pediatric classification; however, age grouping is proposed as some specific forms are more prevalent in infancy (developmental and growth abnormalities, surfactant dysfunction mutations, etc.) and others are usually seen in older cohorts (disorders in normal or immunocompromised hosts, systemic diseases, etc.). Clinical manifestations vary from mild nonspecific symptoms (recurrent respiratory infections, exercise intolerance, failure to thrive, dry cough, etc.) to a severe clinical picture (respiratory distress) and presentation related to the child's age. The diagnostic approach relies on imaging techniques (CT), but further investigations including genetic tests, BAL, and lung biopsy (VATS) are needed in uncertain cases. Pharmacological treatment is mostly empiric and based on anti-inflammatory and immunomodulatory drugs. Lung transplantation for selected cases in a pediatric transplantation center could be an option; however, limited data and evidence are available regarding long-term survival. International collaboration is warranted to understand chILD entities better and improve the outcomes of these patients.

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.

Descriptive and Functional Genomics in Neonatal Respiratory Distress Syndrome: From Lung Development to Targeted Therapies

In this up-to-date study, we first aimed to highlight the genetic and non-genetic factors associated with respiratory distress syndrome (RDS) while also focusing on the genomic aspect of this condition. Secondly, we discuss the treatment options and the progressing therapies based on RNAs or gene therapy. To fulfill this, our study commences with lung organogenesis, a highly orchestrated procedure guided by an intricate network of conserved signaling pathways that ultimately oversee the processes of patterning, growth, and differentiation. Then, our review focuses on the molecular mechanisms contributing to both normal and abnormal lung growth and development and underscores the connections between genetic and non-genetic factors linked to neonatal RDS, with a particular emphasis on the genomic aspects of this condition and their implications for treatment choices and the advancing therapeutic approaches centered around RNAs or gene therapy.

Developmental lung disease in a cat associated with high probability of severe pulmonary hypertension: natural history, histopathology and genetic analysis

Case summary

This report describes the diagnostic findings, natural history and genetic analysis of the candidate gene Forkhead Box F1 (FOXF1) in a young cat with developmental lung disease and high probability of pulmonary hypertension. A 1-year-old male entire Chartreux cat was referred for cardiac murmur investigation and exercise intolerance. Echocardiography identified a high-velocity tricuspid regurgitant jet with right-sided cardiac changes, supporting a high probability of pulmonary hypertension. No congenital cardiac shunts or left-sided cardiac changes were found to support a primary cardiac cause of pulmonary hypertension. Extensive laboratory work, thoracic radiographs and CT were performed. Histopathological characterisation (lung biopsy and later post mortem) was necessary to reach the final diagnosis. Eight months after diagnosis, the cat developed right-sided congestive heart failure, eventually leading to euthanasia. Survival from diagnosis to death was 12 months.

Relevance and novel information

Developmental lung disease belongs to a group of diffuse lung diseases in humans associated with pulmonary hypertension. The veterinary literature describing lung growth disorders in cats is sparse, and the present report provides information on clinical presentation and progression alongside a thorough diagnostic workup, which may aid clinicians in identifying this condition. Lung biopsy was pivotal in reaching the final diagnosis. No causal variants in FOXF1 were identified.

Clinical nomogram assisting in discrimination of juvenile dermatomyositis-associated interstitial lung disease

OBJECTIVE

To establish a prediction model using non-invasive clinical features for early discrimination of DM-ILD in clinical practice.

METHOD

Clinical data of pediatric patients with JDM were retrospectively analyzed using machine learning techniques. The early discrimination model for JDM-ILD was established within a patient cohort diagnosed with JDM at a children's hospital between June 2015 and October 2022.

RESULTS

A total of 93 children were included in the study, with the cohort divided into a discovery cohort (n = 58) and a validation cohort (n = 35). Univariate and multivariate analyses identified factors associated with JDM-ILD, including higher ESR (OR, 3.58; 95% CI 1.21-11.19, P = 0.023), higher IL-10 levels (OR, 1.19; 95% CI, 1.02-1.41, P = 0.038), positivity for MDA-5 antibodies (OR, 5.47; 95% CI, 1.11-33.43, P = 0.045). A nomogram was developed for risk prediction, demonstrating favorable discrimination in both the discovery cohort (AUC, 0.736; 95% CI, 0.582-0.868) and the validation cohort (AUC, 0.792; 95% CI, 0.585-0.930). Higher nomogram scores were significantly associated with an elevated risk of disease progression in both the discovery cohort (P = 0.045) and the validation cohort (P = 0.017).

CONCLUSION

The nomogram based on the ESIM predictive model provides valuable guidance for the clinical evaluation and long-term prognosis prediction of JDM-ILD.

A rare presentation of childhood interstitial lung disease attributed to KDM3B gene mutation: a case report

Childhood Interstitial Lung Disease (chILD) encompasses various respiratory conditions affecting children's lung airspaces and tissues, with diverse causes. One rare cause involves structural vascular changes. We describe a case of a 10-year-old boy diagnosed with chILD who exhibited specific dysmorphic features, developmental delay, and intellectual disability. He was diagnosed with severe pulmonary arterial hypertension (PAH) due to venous thromboembolic disease, an unusual underlying condition for chILD. A Whole Exome Sequence showed mutations in KDM3B and SIN3A genes, respectively responsible for Diets-Jongmans syndrome (DIJOS) and Witteveen-Kolk syndrome (WITKOS). Both syndromes can explain our patient´s phenotype and KDM3B mutation has been previously described to be associated with PAH. Our case suggests a potential association between KDM3B mutation and PAH leading to chILD. It also enriches the knowledge of genotypic diversity in KDM3B and SIN3A genes as well as the spectrum of clinical associations with DIJOS and WITKOS syndromes.

Variants in FGF10 cause early onset of severe childhood interstitial lung disease: A detailed description of four affected children

INTRODUCTION

Fibroblast growth factor 10 (FGF10) is a signaling molecule with a well-established role for lung branching morphogenesis. Rare heterozygous, deleterious variants in the FGF10 gene are known causes of the lacrimo-auriculo-dento-digital (LADD) syndrome and aplasia of lacrimal and salivary glands. Previous studies indicate that pathogenic variants in FGF10 can cause childhood Interstitial Lung Disease (chILD) due to severe diffuse developmental disorders of the lung, but detailed reports on clinical presentation and follow-up of affected children are lacking.

METHODS

We describe four children with postnatal onset of chILD and heterozygous variants in FGF10, each detected by exome or whole genome sequencing.

RESULTS

All children presented with postnatal respiratory failure. Two children died within the first 2 days of life, one patient died at age of 12 years due to right heart failure related to severe pulmonary hypertension (PH) and one patient is alive at age of 6 years, but still symptomatic. Histopathological analysis of lung biopsies from the two children with early postpartum demise revealed diffuse developmental disorder representing acinar dysplasia and interstitial fibrosis. Sequential biopsies of the child with survival until the age of 12 years revealed alveolar simplification and progressive interstitial fibrosis.

DISCUSSION

Our report extends the phenotype of FGF10-related disorders to early onset chILD with progressive interstitial lung fibrosis and PH. Therefore, FGF10-related disorder should be considered even without previously described syndromic stigmata in children with postnatal respiratory distress, not only when leading to death in the neonatal period but also in case of persistent respiratory complaints and PH.

Genetics of bronchopulmonary dysplasia: An update

Bronchopulmonary dysplasia (BPD) is a multi-factorial disease that results from multiple clinical factors, including lung immaturity, mechanical ventilation, oxidative stress, pulmonary congestion due to increasing cardiac blood shunting, nutritional and immunological factors. Twin studies have indicated that susceptibility to BPD can be strongly inherited in some settings. Studies have reported associations between common genetic variants and BPD in preterm infants. Recent genomic studies have highlighted a potential role for molecular pathways involved in inflammation and lung development in affected infants. Rare mutations in genes encoding the lipid transporter ATP-binding cassette, sub-family A, member 3 (ABCA3 gene) which is involved in surfactant synthesis in alveolar type II cells, as well as surfactant protein B (SFTPB) and C (SFTPC) can also result in severe form of neonatal-onset interstitial lung diseases and may also potentially affect the course of BPD. This chapter summarizes the current state of knowledge on the genetics of BPD.

Defining and Promoting Pediatric Pulmonary Health: Developing Biomarkers for Pulmonary Health

Children with inherited and/or acquired respiratory disorders often arrive in adolescence and adulthood with diminished lung function that might have been detected and prevented had better mechanisms been available to identify and to assess progression of disease. Fortunately, advances in genetic assessments, low-cost diagnostics, and minimally- invasive novel biomarkers are being developed to detect and to treat respiratory diseases before they give rise to loss of life or lung function. This paper summarizes the Developing Biomarkers for Pulmonary Health sessions of the National Heart, Lung, and Blood Institute- sponsored 2021 Defining and Promoting Pediatric Pulmonary Health workshop. These sessions discussed genetic testing, pulse oximetry, exhaled nitric oxide, and novel biomarkers related to childhood lung diseases.

Out of the box diagnosis in a child treated as childhood interstitial lung disease- William-Campbell syndrome

A 9-year-old school-going boy was referred to us for evaluation of childhood interstitial lung disease (chILD), with complaints of persisting dry cough, since the newborn period, tachypnea at rest, and failure to gain weight. Upon evaluation his findings were consistent with William-Campbell syndrome (WCS). He was advised for airway clearance technique (ACT) and was started on Bipap at night for splinting of the airways.

Genetics in Idiopathic Pulmonary Fibrosis: A Clinical Perspective

BACKGROUND

Unraveling the genetic background in a significant proportion of patients with both sporadic and familial IPF provided new insights into the pathogenic pathways of pulmonary fibrosis.

AIM

The aim of the present study is to overview the clinical significance of genetics in IPF.

PERSPECTIVE

It is fascinating to realize the so-far underestimated but dynamically increasing impact that genetics has on aspects related to the pathophysiology, accurate and early diagnosis, and treatment and prevention of this devastating disease. Genetics in IPF have contributed as no other in unchaining the disease from the dogma of a "a sporadic entity of the elderly, limited to the lungs" and allowed all scientists, but mostly clinicians, all over the world to consider its many aspects and "faces" in all age groups, including its co-existence with several extra pulmonary conditions from cutaneous albinism to bone-marrow and liver failure.

CONCLUSION

By providing additional evidence for unsuspected characteristics such as immunodeficiency, impaired mucus, and surfactant and telomere maintenance that very often co-exist through the interaction of common and rare genetic variants in the same patient, genetics have created a generous and pluralistic yet unifying platform that could lead to the understanding of the injurious and pro-fibrotic effects of many seemingly unrelated extrinsic and intrinsic offending factors. The same platform constantly instructs us about our limitations as well as about the heritability, the knowledge and the wisdom that is still missing.

The Challenging Diagnosis of Interstitial Lung Disease in Children-One Case Report and Literature Review

Childhood interstitial lung disease (chILD) includes a heterogeneous spectrum of rare respiratory disorders in children associated with substantial morbi-mortality. Interstitial tissue, and other pulmonary structures, epithelium, blood vessels, or pleura are involved, resulting in a restrictive lung disfunction. Respiratory symptoms set in progressively and are often subtle, making thorough clinical history and physical examination fundamental. The etiology often is obscure. The clinical presentation mimics pneumonia or asthma, leading to a diagnostic delay. Challenging diagnosis may require genetic tests, bronchoalveolar lavage, or lung biopsy. Alongside general supportive therapeutic measures, anti-inflammatory, immunosuppressive or antifibrotic agents may be used, based on data derived from adult studies. However, if accurate diagnosis and treatment are delayed, irreversible chronic respiratory failure may ensue, impacting prognosis. The most frequent chILD is hypersensitivity pneumonitis (HP), although it is rare in children. HP is associated with exposure to an environmental antigen, resulting in inflammation of the airways. Detailed antigen exposure history and identification of the inciting trigger are the cornerstones of diagnostic. This article provides the current state of chILD, revealing specific features of HP, based on a clinical case report of a patient admitted in our clinic, requiring extensive investigations for diagnosis, with a favorable long-term outcome.