Genetic causes and clinical management of pediatric interstitial lung diseases

Hypomorphic pathogenic variant in SFTPB leads to adult pulmonary fibrosis

Biallelic pathogenic variants in the surfactant protein (SP)-B gene (SFTPB) have been associated with fatal forms of interstitial lung diseases (ILD) in newborns and exceptional survival in young children. We herein report the cases of two related adults with pulmonary fibrosis due to a new homozygous SFTPB pathogenic variant, c.582G>A p.(Gln194=). In vitro transcript studies showed that this SFTPB synonymous pathogenic variant induces aberrant splicing leading to three abnormal transcripts with the preservation of the expression of a small proportion of normal SFTPB transcripts. Immunostainings on lung biopsies of the proband showed an almost complete loss of SP-B expression. This hypomorphic splice variant has thus probably allowed the patients' survival to adulthood while inducing an epithelial cell dysfunction leading to ILD. Altogether, this report shows that SFTPB pathogenic variants should be considered in atypical presentations and/or early-onset forms of ILD particularly when a family history is identified.

Diagnostic workup of childhood interstitial lung disease

Childhood interstitial lung diseases (chILDs) are rare and heterogeneous diseases with significant morbidity and mortality. An accurate and quick aetiological diagnosis may contribute to better management and personalised treatment. On behalf of the European Respiratory Society Clinical Research Collaboration for chILD (ERS CRC chILD-EU), this review summarises the roles of the general paediatrician, paediatric pulmonologists and expert centres in the complex diagnostic workup. Each patient's aetiological chILD diagnosis must be reached without prolonged delays in a stepwise approach from medical history, signs, symptoms, clinical tests and imaging, to advanced genetic analysis and specialised procedures including bronchoalveolar lavage and biopsy, if necessary. Finally, as medical progress is fast, the need to revisit a diagnosis of "undefined chILD" is stressed.

Rare surfactant-related variants in familial and sporadic pulmonary fibrosis

The role of constitutional genetic defects in idiopathic pulmonary fibrosis (IPF) is increasingly appreciated. Monogenic disorders associated with IPF affect two pathways: telomere maintenance, accounting for approximately 10% of all patients with IPF, and surfactant biology, responsible for 1%-3% of cases and often co-occurring with lung cancer. We examined the prevalence of rare variants in five surfactant-related genes, SFTPA1, SFPTA2, SFTPC, ABCA3, and NKX2-1, that were previously linked to lung disease in whole genome sequencing data from 431 patients with IPF. We identified functionally deleterious rare variants in SFTPA2 with a prevalence of 1.3% in individuals with and without a family history of IPF. All individuals had no personal history of lung cancer, but substantial bronchiolar metaplasia was noted on lung explants and biopsies. Five patients had novel missense variants in NKX2-1, but the contribution to disease is unclear. In general, patients were younger and had longer telomeres compared with the majority of patients with IPF suggesting that these features may be useful for identifying this subset of patients in the clinic. These data suggest that SFTPA2 variants may be more common in unselected IPF cohorts and may manifest in the absence of personal/family history of lung cancer or IPF.

Congenital Surfactant C Deficiency with Pulmonary Hypertension-A Case Report

Interstitial lung diseases in children are a diverse group in terms of etiology and pathogenesis. With advances in genetic testing, mutations in surfactant protein have now been identified as the etiology for childhood interstitial lung disease of variable onset and severity, ranging from fatal acute respiratory distress syndrome (RDS) in neonates to chronic lung disease in adults. We presented an 11-month-old girl with surfactant protein C deficiency and secondary pulmonary hypertension, successfully treated with hydroxychloroquine, and provided a detailed discussion of the clinical and diagnostic approach and management.

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

Children's interstitial lung disease (chILD) encompasses a wide and heterogeneous spectrum of diseases substantially different from that of adults. Established classification systems divide chILD into conditions more prevalent in infancy and other conditions occurring at any age. This categorisation is based on a multidisciplinary approach including clinical, radiological, genetic and histological findings. The diagnostic evaluation may include lung biopsies if other diagnostic approaches failed to identify a precise chILD entity, or if severe or refractory respiratory distress of unknown cause is present. As the majority of children will be evaluated and diagnosed outside of specialist centres, this review summarises relevant clinical, genetic and histological findings of chILD to provide assistance in clinical assessment and rational diagnostics.

ILD of childhood is comparable by name only to lung disease in adults. A dedicated interdisciplinary team is required to achieve the best possible outcome. This review summarises the current clinicopathological criteria and associated genetic alterations.https://bit.ly/3mpxI3b

RaDiCo, the French national research program on rare disease cohorts

BACKGROUND

Rare diseases (RDs) affect nearly 3 million people in France and at least 26-30 million people in Europe. These diseases, which represent a major medical concern, are mainly of genetic origin, often chronic, progressive, degenerative, life threatening and disabling, accounting for more than one third of all deaths occurring during infancy. In this context, there are needs for coordinated information on RDs at national/international levels, based on high quality, interoperable and sharable data. The main objective of the RaDiCo (Rare Disease Cohorts) program, coordinated by Inserm, was the development of RD e-cohorts via a national platform. The cohort projects were selected through a national call in 2014. The e-cohorts are supported by an interoperable platform, equivalent to an infrastructure, constructed on the "cloud computing" principle and in compliance with the European General Data Protection Regulation. It is dedicated to allow a continuous monitoring of data quality and consistency, in line with the French Health Data Hub.

RESULTS

Depending on cohorts, the objectives are to describe the natural history of the studied RD(s), identify the underlying disease genes, establish phenotype-genotype correlations, decipher their pathophysiology, assess their societal and medico-economic impact, and/or identify patients eligible for new therapeutic approaches. Inclusion of prevalent and incident cases started at the end of 2016. As of April 2021, 5558 patients have been included within 13 RD e-cohorts covering 67 diseases integrated in 10 European Reference Networks and contributing to the European Joint Program on RDs. Several original results have been obtained in relation with the secondary objectives of the RaDiCo cohorts. They deal with discovery of new disease genes, assessment of treatment management, deciphering the underlying pathophysiological mechanisms, diagnostic approaches, genotype-phenotype relationships, development and validation of questionnaires relative to disease burden, or methodological aspects.

CONCLUSION

RaDiCo currently hosts 13 RD e-cohorts on a sharable and interoperable platform constructed on the "cloud computing" principle. New RD e-cohorts at the European and international levels are targeted.

Genetic disorders of the surfactant system: focus on adult disease

Genes involved in the production of pulmonary surfactant are crucial for the development and maintenance of healthy lungs. Germline mutations in surfactant-related genes cause a spectrum of severe monogenic pulmonary diseases in patients of all ages. The majority of affected patients present at a very young age, however, a considerable portion of patients have adult-onset disease. Mutations in surfactant-related genes are present in up to 8% of adult patients with familial interstitial lung disease (ILD) and associate with the development of pulmonary fibrosis and lung cancer.High disease penetrance and variable expressivity underscore the potential value of genetic analysis for diagnostic purposes. However, scarce genotype-phenotype correlations and insufficient knowledge of mutation-specific pathogenic processes hamper the development of mutation-specific treatment options.This article describes the genetic origin of surfactant-related lung disease and presents spectra for gene, age, sex and pulmonary phenotype of adult carriers of germline mutations in surfactant-related genes.

Functional assessment and phenotypic heterogeneity of SFTPA1 and SFTPA2 mutations in interstitial lung diseases and lung cancer

INTRODUCTION

Interstitial lung diseases (ILDs) can be caused by mutations in the SFTPA1 and SFTPA2 genes, which encode the surfactant protein (SP) complex SP-A. Only 11 SFTPA1 or SFTPA2 mutations have so far been reported worldwide, of which five have been functionally assessed. In the framework of ILD molecular diagnosis, we identified 14 independent patients with pathogenic SFTPA1 or SFTPA2 mutations. The present study aimed to functionally assess the 11 different mutations identified and to accurately describe the disease phenotype of the patients and their affected relatives.

METHODS

The consequences of the 11 SFTPA1 or SFTPA2 mutations were analysed both in vitro, by studying the production and secretion of the corresponding mutated proteins and ex vivo, by analysing SP-A expression in lung tissue samples. The associated disease phenotypes were documented.

RESULTS

For the 11 identified mutations, protein production was preserved but secretion was abolished. The expression pattern of lung SP-A available in six patients was altered and the family history reported ILD and/or lung adenocarcinoma in 13 out of 14 families (93%). Among the 28 SFTPA1 or SFTPA2 mutation carriers, the mean age at ILD onset was 45 years (range 0.6-65 years) and 48% underwent lung transplantation (mean age 51 years). Seven carriers were asymptomatic.

DISCUSSION

This study, which expands the molecular and clinical spectrum of SP-A disorders, shows that pathogenic SFTPA1 or SFTPA2 mutations share similar consequences for SP-A secretion in cell models and in lung tissue immunostaining, whereas they are associated with a highly variable phenotypic expression of disease, ranging from severe forms requiring lung transplantation to incomplete penetrance.

Identification of a Missense Mutation in the Surfactant Protein A2 Gene in a Chinese Family with Interstitial Lung Disease

Interstitial lung disease (ILD) is a large group of disorders, most of which lead to progressive scarring of lung tissue. The scarring associated with ILD eventually affects your ability to breathe and get enough oxygen into your bloodstream. The typical symptoms of ILD are shortness of breath at rest or aggravated by exertion and dry cough. In this study, we enrolled a family with ILDs from central south region of China. Three patients suffered from repeated cough and shortness of breath. The high resolution computed tomography (HRCT) testing further confirmed the diagnosis of interstitial lung lesions. Whole exome sequencing (WES) and Sanger sequencing were applied to detect the genetic lesion of the family. By employing WES, a novel heterozygous mutation (NM_001098668: c.554C>T/p.A185V) of surfactant protein A2 (SFTPA2) was identified in the affected individuals and absent in the healthy members. Bioinformatics analysis predicted that this mutation is disease-causing mutation and located in an evolutionarily conserved site of SFTPA2 protein. The novel mutation may disrupt the stability of SFTPA2 protein and induce endoplasmic reticulum stress, finally leading to ILD under the influence of microorganisms. Our study not only expands the spectrum of SFTPA2 mutations but also helps the family members to mitigate ILD risk factors. The study also supplements and improves genetic testing strategies and ILD risk estimation methodologies for China.

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.

Heme oxygenase-1 deficiency presenting with interstitial lung disease and hemophagocytic flares

BACKGROUND

Heme oxygenase-1 (HMOX1) catalyzes the metabolism of heme into carbon monoxide, ferrous iron, and biliverdin. Through biliverdin reductase, biliverdin becomes bilirubin. HMOX1-deficiency is a rare autosomal recessive disorder with hallmark features of direct antibody negative hemolytic anemia with normal bilirubin, hyperinflammation and features similar to macrophage activation syndrome. Clinical findings have included asplenia, nephritis, hepatitis, and vasculitis. Pulmonary features and evaluation of the immune response have been limited.

CASE PRESENTATION

We present a young boy who presented with chronic respiratory failure due to nonspecific interstitial pneumonia following a chronic history of infection-triggered recurrent hyperinflammatory flares. Episodes included hemolysis without hyperbilirubinemia, immunodeficiency, hepatomegaly with mild transaminitis, asplenia, leukocytosis, thrombocytosis, joint pain and features of macrophage activation with negative autoimmune serologies. Lung biopsy revealed cholesterol granulomas. He was found post-mortem by whole exome sequencing to have a compound heterozygous paternal frame shift a paternal frame shift HMOX1 c.264_269delCTGG (p.L89Sfs*24) and maternal splice donor HMOX1 (c.636 + 2 T > A) consistent with HMOX1 deficiency. Western blot analysis confirmed lack of HMOX1 protein upon oxidant stimulation of the patient cells.

CONCLUSIONS

Here, we describe a phenotype expansion for HMOX1-deficiency to include not only asplenia and hepatomegaly, but also interstitial lung disease with cholesterol granulomas and inflammatory flares with hemophagocytosis present in the bone marrow.

Child-Adult Transition in Sarcoidosis: A Series of 52 Patients

(1) Background: Pediatric sarcoidosis is a rare and mostly severe disease. Very few pediatric series with a prolonged follow-up are reported. We aimed to evaluate the evolution of pediatric sarcoidosis in adulthood. (2) Material and methods: Patients over 18-years-old with a pediatric-onset sarcoidosis (≤15-year-old) who completed at least a three-year follow-up in French expert centers were included. Clinical information at presentation and outcome in adulthood were studied. (3) Results: A total of 52 patients were included (34 prospectively in childhood and 18 retrospectively in adulthood), with a mean age of 12 (±2.7) at diagnosis. The median duration time of follow-up was 11.5 years (range 3–44.5). Relapses mostly occurred during treatment decrease (84.5%), others within the three years after treatment interruption (9.1%), and rarely when the disease was stable for more than three years (6.4%). Sarcoidosis was severe in 11 (21.2%) in adulthood. Patients received a high corticosteroid cumulative dose (median 17,900 mg) for a median duration of five years (range 0–32), resulting in mostly mild (18; 35.3%) and rarely severe (2; 3.8%) adverse events. (4) Conclusions: Pediatric-onset sarcoidosis needed a long-term treatment in almost half of the patients. Around one fifth of pediatric-onset sarcoidosis patients had severe sarcoidosis consequences in adulthood.

Recognizing genetic disease: A key aspect of pediatric pulmonary care

Advancement in technology has improved recognition of genetic etiologies of disease, which has impacted diagnosis and management of rare disease patients in the pediatric pulmonary clinic. This review provides an overview of genetic conditions that are likely to present with pulmonary features and require extensive care by the pediatric pulmonologist. Increased familiarity with these conditions allows for improved care of these patients by reducing time to diagnosis, tailoring management, and prompting further investigation into these disorders.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in children (chILD) is a heterogeneous group of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. The pathogenesis of the various chILD is complex and the diseases share common features of inflammatory and fibrotic changes of the lung parenchyma that impair gas exchanges. The etiologies of chILD are numerous. In this review, we chose to classify them as ILD related to exposure/environment insults, ILD related to systemic and immunological diseases, ILD related to primary lung parenchyma dysfunctions and ILD specific to infancy. A growing part of the etiologic spectrum of chILD is being attributed to molecular defects. Currently, the main genetic mutations associated with chILD are identified in the surfactant genes SFTPA1, SFTPA2, SFTPB, SFTPC, ABCA3 and NKX2-1. Other genetic contributors include mutations in MARS, CSF2RA and CSF2RB in pulmonary alveolar proteinosis, and mutations in TMEM173 and COPA in specific auto-inflammatory forms of chILD. However, only few genotype-phenotype correlations could be identified so far. Herein, information is provided about the clinical presentation and the diagnosis approach of chILD. Despite improvements in patient management, the therapeutic strategies are still relying mostly on corticosteroids although specific therapies are emerging. Larger longitudinal cohorts of patients are being gathered through ongoing international collaborations to improve disease knowledge and targeted therapies. Thus, it is expected that children with ILD will be able to reach the adulthood transition in a better condition.

Pulmonary alveolarproteinosis in children

Pulmonary alveolar proteinosis (PAP) is an umbrella term for a wide spectrum of conditions that have a very characteristic appearance on computed tomography. There is outlining of the secondary pulmonary lobules on the background of ground-glass shadowing and pathologically, filling of the alveolar spaces with normal or abnormal surfactant. PAP is rare and the common causes in children are very different from those seen in adults; autoimmune PAP is rare and macrophage blockade not described in children. There are many genetic causes of PAP, the best known of which are mutations in the genes encoding surfactant protein (SP)-B, SP-C, thyroid transcription factor 1, ATP-binding cassette protein 3, and the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor α- and β- chains. PAP may also be a manifestation of rheumatological and metabolic disease, congenital immunodeficiency, and haematological malignancy. Precise diagnosis of the underlying cause is essential in planning treatment, as well as for genetic counselling. The evidence base for treatment is poor. Some forms of PAP respond well to whole-lung lavage, and autoimmune PAP, which is much commoner in adults, responds to inhaled or subcutaneous GM-CSF. Emerging therapies based on studies in murine models of PAP include stem-cell transplantation for GM-CSF receptor mutations.

EDUCATIONAL AIMS

To understand when to suspect that a child has pulmonary alveolar proteinosis (PAP) and how to confirm that this is the cause of the presentation.To show that PAP is an umbrella term for conditions characterised by alveolar filling by normal or abnormal surfactant, and that this term is the start, not the end, of the diagnostic journey.To review the developmental differences in the spectrum of conditions that may cause PAP, and specifically to understand the differences between causes in adults and children.To discuss when to treat PAP with whole-lung lavage and/or granulocyte-macrophage colony-stimulating factor, and review potential promising new therapies.

Clinical heterogeneity of Pulmonary Arterial Hypertension associated with variants in TBX4

Background

The knowledge of hereditary predisposition has changed our understanding of Pulmonary Arterial Hypertension. Genetic testing has been widely extended and the application of Pulmonary Arterial Hypertension specific gene panels has allowed its inclusion in the diagnostic workup and increase the diagnostic ratio compared to the traditional sequencing techniques. This is particularly important in the differential diagnosis between Pulmonary Arterial Hypertension and Pulmonary Venoocclusive Disease.

Methods

Since November 2011, genetic testing is offered to all patients with idiopathic, hereditable and associated forms of Pulmonary Arterial Hypertension or Pulmonary Venoocclusive Disease included in the Spanish Registry of Pulmonary Arterial Hypertension. Herein, we present the clinical phenotype and prognosis of all Pulmonary Arterial Hypertension patients with disease-associated variants in TBX4.

Results

Out of 579 adults and 45 children, we found in eight patients from seven families, disease-causing associated variants in TBX4. All adult patients had a moderate-severe reduction in diffusion capacity. However, we observed a wide spectrum of clinical presentations, including Pulmonary Venoocclusive Disease suspicion, interstitial lung disease, pulmonary vascular abnormalities and congenital heart disease.

Conclusions

Genetic testing is now essential for a correct diagnosis work-up in Pulmonary Arterial Hypertension. TBX4-associated Pulmonary Arterial Hypertension has marked clinical heterogeneity. In this regard, a genetic study is extremely useful to obtain an accurate diagnosis and provide appropriate management.

Pulmonary Fibrosis in Children

: Pulmonary fibrosis (PF) is a very rare condition in children, which may be observed in specific forms of interstitial lung disease. None of the clinical, radiological, or histological descriptions used for PF diagnosis in adult patients, especially in situations of idiopathic PF, can apply to pediatric situations. This observation supports the view that PF expression may differ with age and, most likely, may cover distinct entities. The present review aims at summarizing the current understanding of PF pathophysiology in children and identifying suitable diagnostic criteria.

Health-related quality of life in infants and children with interstitial lung disease

INTRODUCTION

Interstitial lung disease in children (chILD) is a highly heterogeneous group of rare and severe respiratory disorders. The disease by itself, the burden of the treatments (oxygen therapy, corticosteroid pulses, nutritional support) and recurrent hospitalizations may impair the quality of life (QoL) of these children. The aim of the study was to compare the health-related QoL (HR-QoL) in chILD compared to a healthy population and to find out the predictive factors of an altered QoL.

METHODS

Patients aged 1 month to 18 years with ILD of known or unknown etiology were prospectively included. Parents and children over 8 years old were asked to fill the PedsQL 4.0 Generic Core Scale ranging from 0 to 100 points.

RESULTS

A total of 78 children were recruited in 13 French pediatric centers. Total scores were 11.94 points (P = 0.0003) less for child self-report and 14.08 points ( P < 0.0001) less for parent proxy-report with respect to the healthy population. The clinical factors associated with a lower total score were: extrapulmonary expression of the disease, higher Fan severity score, long-term oxygen therapy, nutritional support, and a number of oral treatments.

CONCLUSION

Using a validated quality of life (QoL) scale, we showed that health-related-QoL is significantly impaired in chILD compared with a healthy population. Factors altering QoL score are easy to recognize and could help identify children at a heightened risk of low QoL.

STING-dependent sensing of self-DNA drives silica-induced lung inflammation

Silica particles induce lung inflammation and fibrosis. Here we show that stimulator of interferon genes (STING) is essential for silica-induced lung inflammation. In mice, silica induces lung cell death and self-dsDNA release in the bronchoalveolar space that activates STING pathway. Degradation of extracellular self-dsDNA by DNase I inhibits silica-induced STING activation and the downstream type I IFN response. Patients with silicosis have increased circulating dsDNA and CXCL10 in sputum, and patients with fibrotic interstitial lung disease display STING activation and CXCL10 in the lung. In vitro, while mitochondrial dsDNA is sensed by cGAS-STING in dendritic cells, in macrophages extracellular dsDNA activates STING independent of cGAS after silica exposure. These results reveal an essential function of STING-mediated self-dsDNA sensing after silica exposure, and identify DNase I as a potential therapy for silica-induced lung inflammation.

Silica particles induce intereukin-1 (IL-1) response to contribute to lung inflammation, but the underlying mechanism is unclear. Here the authors show that silica induces cell death and release of mitochondria and genomic DNA, which are sensed by STING with or without involving cGAS, respectively, for IL-1 induction and lung inflammation.

Chronic interstitial lung diseases in children: diagnosis approaches

Introduction: Children interstitial lung disease (chILD) is a heterogeneous group of rare respiratory disorders characterized by inflammatory and fibrotic changes of the lung parenchyma. They include ILD related to exposure/environment insults, ILD related to systemic diseases processes, ILD related to primary lung parenchyma dysfunctions and ILD specific to infancy. Areas covered: This review provides an update on chILD pathophysiology and diagnosis approaches in immunocompetent children. It includes current information on genetic causes. Expert commentary: ChILD covers a large spectrum of entities with heterogeneous disease expression. Various classifications have been reported, but none of them seems completely satisfactory. Recently, progress in molecular genetics has allowed identifying some genetic contributors, with, so far, a lack of correlations between gene disorders and disease expression. Despite improvements in patient management, chILD prognosis is still burdened by significant morbidity and mortality. Ongoing international collaborations will allow gathering larger longitudinal cohorts of patients to improve disease knowledge and personalized care. The overall goal is to help the children with ILD to reach the adulthood transition in a better condition, and to structure genetic counseling for their family.