Pulmonary alveolar proteinosis (PAP) is a rare syndrome where surfactant accumulates in the alveolar macrophages, leading to impaired gas exchange, dyspnea, hypoxia, and respiratory failure in some cases. The key regulator of alveolar macrophage maturity and function is granulocyte macrophage colony-stimulating factor (GM-CSF), and dysfunctional signaling is the key pathogenic driver of primary PAP.1,2 Primary PAP can be caused by either anti-GM-CSF autoantibodies in autoimmune PAP or mutations in CSF2RA or CSF2RB, encoding the a and b subunits of the GM-CSF receptor, respectively, in hereditary PAP (hPAP).3,4 Whole-lung lavage is the current treatment for hPAP but is not FDA approved, and while bone marrow, stem cell, and lung transplantations have been trialed in hPAP with some success, these therapies are limited by infection and graft rejection.

proteinosis (aPAP) is an ultra-rare lung disease characterised by myeloid cell dysfunction, abnormal pulmonary surfactant accumulation resulting in progressive dyspnoea of insidious onset and respiratory failure, innate immune deficiency and secondary infection. 1 2 Autoantibodies that bind GM-CSF (granulocyte/macrophage colony-stimulating factor) drive the pathogenesis, primarily causing alveolar macrophage dysfunction, resulting in an inability to recycle surfactant and cell debris. 1 3 Secondary infections are relatively common in aPAP and can include both common and opportunistic pathogens. Infections can be present at disease onset, and indeed at times have been hypothesised to cause secondary PAP. 4 Importantly, approximately one-fifth of deaths related to PAP syndrome can be related to secondary infection. 4 GM-CSF signalling is central to the healthy differentiation, proliferation and maturation of alveolar macrophages, ensuring maintenance of surfactant homoeostasis and innate host defence responses. GM-CSF modulates these functions via transcription factor PU.1. 5 GM-CSF influences macrophage cytokine production, specifically tumour necrosis factor-α (TNF-α ) and interleukin-6, which can have proinflammatory and anti-inflammatory effects through engagement of the CD14 receptor by lipopolysaccharide (LPS). 6 GM-CSF knockout mice showed pathological changes similar to those seen in patients with aPAP with accumulation of surfactant phospholipids and proteins. 5 These mice are more susceptible to infection, have delayed bacteria clearance and demonstrate increased mortality from infection. 7

BACKGROUND:Pulmonary alveolar proteinosis (PAP) is a rare syndrome caused by several distinct diseases leading to progressive dyspnoea, hypoxaemia, risk of respiratory failure and early death due to accumulation of proteinaceous material in the lungs. Diagnostic strategies may include computed tomography (CT) of the lungs, bronchoalveolar lavage (BAL), evaluation of antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), genetic testing and, eventually, lung biopsy. The management options are focused on removing the proteinaceous material by whole lung lavage (WLL), augmentation therapy with GM-CSF, rituximab, plasmapheresis and lung transplantation. The presented diagnostic and management guidelines aim to provide guidance to physicians managing patients with PAP. METHODS:A European Respiratory Society Task Force composed of clinicians, methodologists and patients with experience in PAP developed recommendations in accordance with the ERS Handbook for Clinical Practice Guidelines and the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) approach. This included a systematic review of the literature and application of the GRADE approach to assess the certainty of evidence and strength of recommendations. The Task Force formulated five PICO (Patients, Intervention, Comparison, Outcomes) questions and two narrative questions to develop specific evidence-based recommendations. RESULTS:The Task Force developed recommendations for the five PICO questions. These included management of PAP with WLL, GM-CSF augmentation therapy, rituximab, plasmapheresis and lung transplantation. Also, the Task Force made recommendations regarding the use of GM-CSF antibody testing, diagnostic BAL and biopsy based on the narrative questions. In addition to the recommendations, the Task Force provided information on the hierarchy of diagnostic interventions and therapy. CONCLUSIONS:The diagnosis of PAP is based on CT and BAL cytology or lung histology, whereas the diagnosis of specific PAP-causing diseases requires GM-CSF antibody testing or genetic analysis. There are several therapies including WLL and augmentation therapy with GM-CSF available to treat PAP, but supporting evidence is still limited.

Pulmonary fibrosis (PF) can be idiopathic or driven by a specific insult, genetic susceptibility, or disease process. Inflammation plays a role in the pathophysiology, the extent of which remains a longstanding topic of debate. More recently, there has been increasing interest in a potential inciting role for aberrant lipid metabolism. Lipids are essential for the structure and function of all cell membranes, but specifically in the lung for surfactant composition, intra- and intercellular lipid mediators, and lipofibroblasts. Clinically, there is evidence of increased lipid deposition in the subpleural space and at a whole-lung tissue level in PF. There is evidence of increased parenchymal lipid deposition and abnormal mediastinal fat shape on chest computed tomography. A protective role for cholesterol-lowering drugs, including statins and ezetimibe, has been described in PF. At a cellular level, fatty acid, phospholipid, and glucose metabolism are disordered, as is the production of lipid mediators. Here we put forward the argument that there is substantive clinical and biological evidence to support a role for aberrant lipid metabolism and lipid mediators in the pathogenesis of PF.

"Updated Prevalence of Lymphangioleiomyomatosis in Europe." American Journal of Respiratory and Critical Care Medicine, 209(4), pp. 456–459

This case describes a woman in her 20s with a 6-month history of progressive exertional dyspnoea and cough. Examination revealed hypoxia on room air, sinus tachycardia, finger clubbing and bibasal inspiratory crackles. Inflammatory markers were mildly elevated and empirical antimicrobial therapy was commenced. A multidisciplinary discussion consensus diagnosis of acute interstitial pneumonitis was made based on the findings of high-resolution CT of the chest, macrophage predominant bronchoalveolar lavage cell differential and surgical lung biopsy. There was clinical and radiological deterioration despite glucocorticoids and antifibrotic therapy. A body mass index of 37.5 kg/m2precluded her from lung transplant assessment and consideration. Following consultation with the weight management service, she was commenced on glucagon-like peptide 1 (GLP-1) analogue therapy. She had a remarkable response within 6 months, was listed for lung transplantation, and within 18 months of her initial presentation, a double lung transplantation was performed.

Introduction: High-resolution computed tomography (HRCT) appearance including low attenuation area is one of the most important indices to evaluate severity of diffuse cystic lung diseases (DCLDs) including lymphangioleiomyomatosis (LAM), Birt-Hogg-Dubé syndrome (BHD) and Lymphatic interstitial lung disease (LIP). Another important evaluation for severity is pulmonary function tests (PFTs). Recently, quantitative HRCT analysis is used for diagnosis and measuring treatment effectiveness in LAM. However, there are few reports on the correlation between PFTs and HRCT using quantitative analysis in DCLDs. Aims and objectives: The aim of this study was to assess the utility of automated 3D cyst analysis in DCLDs and correlation to PFTs. Methods: 35 patients were included, eighteen LAM patients, ten BHD patients, seven LIP patients. HRCT images were interrogated using CT Pulmonary 3D tool on SyngoVia post-processing software (Siemens Healthineers, Erlangen, Germany). Imaging slices were 3mm or less. A cut of range of -900 to -950 Hounsfield Units were used for calculating attenuation area. The measurements of PFTs were set to meet the ATS/ERS instrument quality control standards. Results: We found correlations between the HRCT parameters and PFT. Among these parameters, total lung attenuation volume (tLAV) and FEV1% predicted had the strongest correlations (r= -0.5, p< 0.01). FVC% predicted and FEV1/FVC% also correlated (r= 0.34, p= 0.05, r= -0.46, p<0.01). Interestingly, DLco didn't correlate with cyst volume (r= 0.02). Conclusion: Quantitative 3D HRCT analysis may be helpful tool for the assessment of disease severity in DCLD, this needs to be verified in larger population of DCLDs.

Introduction: There is increasing interest in the role of lipids in processes that modulate fibrosis. Specifically, some inherited surfactant dysfunction disorders result in pulmonary fibrosis. Surfactant consists of phospholipids and smaller quantities of neutral lipids such as cholesterol ester (CE). Tissue lipidomics on mouse bleomycin models demonstrates increased total lipid compared to control. Aims & objectives: To perform lipidomic analysis on human IPF lung tissue and assess the impact of specific lipids on human fibroblasts. Methods: Lung tissue from human IPF and control patients (n=10) were analysed for targeted quantitative measurement of >1,100 lipid species. Primary cell culture of human IPF and control fibroblasts was performed and cells were exposed to lipid species identified as increased on IPF tissue lipidomic analysis. Expression of alpha-smooth muscle actin (aSMA) and collagen 1 (Col1a1) were measured to assess for myofibroblast-like transition following lipid exposure. Results: There was an increase in pulmonary lipid content in patients with IPF compared to control (23.16nmol/mg vs. 18.66nmol/mg, p=0.0317). Specific increases were noted in 16:0, 20:4, and 22:6-containing lipids within both CE and PC species. Dose-related increases in aSMA and Col1a1 protein and RNA expression occur in human fibroblasts exposed to PC-16.0 and decreased expression when exposed to PC-20.4, CE 16.0, and CE 20.4. Conclusions: Abnormal lipid deposition is seen in IPF on lipidomic analysis. Specific lipid subgroups appear to impact fibroblast biology as seen by changes in aSMA and Col1a1 expression. Further investigation is still warranted to identify the specific action of lipids in fibrosis.

Exosomes are a class of extra cellular vesicles (EVs), with a multi vesicular endosomal origin, that are released by all cell types, with sizes ranging from 30-150nm and a lipid bilayer membrane. They have been shown to play key roles in disease progression and have diagnostic and disease monitoring potential. This study aims to characterize exosomes from the serum of patients with Lymphangioleiomyomatosis (LAM), a rare, low-grade, metastasizing neoplasm that occurs predominantly in females. Using Nanoparticle Tracking Analysis (NTA), serum from LAM patients (n=19) have significantly increased numbers of exosomes compared to serum samples from healthy controls (n=20) (8.9x109 vs 13.8x109 particles/ml; p=0.024). Furthermore, particles counts are significantly negatively correlated with the forced expiratory volume (FEV1) (r=-0.4667; p-value=0.0295) in LAM patients. Metalloproteinase activity in exosomes was measured by zymography. Interestingly, these LAM-derived exosomes had significantly higher activity of Pro-MMP-9 (3-fold increase; p-value=0.0278). We analyzed the effects of serum-derived exosomes on cells from an A549 cell line. Increased expression of vimentin, a major marker of EMT, was observed in cells treated with LAM-derived exosomes compared to healthy controls (1.4-fold increase; p=0.0217). Moreover, we showed by a modified Boyden chamber assay that exosomes derived from serum treatment increases the invasive capacity of A549 cells (fold change of 2.2; p-value=0.0004). We interrogated the LAM Single Cell Atlas and identified increased expression of TWIST1, a key transcription factor for EMT. TWIST1 was increased 8-fold in the lung and was uniquely expressed in 'LAM cells', which had metastasized. Furthermore, proteomic analysis revealed high expression of C3 and C5 in LAM-derived exosomes (respectively 1.4- and 2.1-fold change; p=0.0276 and p=0.0034) suggesting the potential regulatory role of the compliment system in the EMT mediated by exosomes These preliminary results highlight the urge to study the specific mechanistic interplay between MMPs and EMT, mediated by exosomes, and whether exosomes are involved in the metastatic spread of LAM cells to the lung and their role in influencing innate and adaptive immune cell response to this invasion. Citation Format: Amina Jouida, Patrick McFadden, Grace Buckley, Evelyn Lynn, O'Callaghan Marissa, Yasuhito Sekimoto, Aurelie Fabre, Michael P. Keane, Cormac McCarthy. The pre-metastatic niche establishment through the induction of the epithelial-to-mesenchymal transition by circulating exosomes in lymphangioleiomyomatosis (LAM): implication of the complement cascade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1230.

Rationale: Myositis-related ILD are a heterogenous group of disorders. Clinical features and presence of autoantibodies determines sub-type with prognostic implications. The aim of this study was to assess how quantitative radiology scores correlated with phenotype. Methods: Retrospective clinical, radiological, serological and therapeutic data was analysed for all myositis-related ILD patients. Semi-quantitative assessment of fibrosis on CT was performed using validated methodology. Results: 14 patients with myositis-related ILD were assessed. Median age at diagnosis was 51.5 yrs, with 64% females. Despite having signs and symptoms consistent with myositis, 21.4% of patients had undetectable auto-antibodies. Reticulation was the most common radiological finding with mean lung involvement of 8% (range:0%-33%), followed by pure ground glass (mean:6.4%; range:0-23%), then honeycombing (mean:1.6%; range 0%-20%). Patients with predominantly lower lobe disease had lower mean % predicted FVC (71+-22% v 92+-16.3%, p=ns) and DLCO (54+-20% v 67+-13%, p=ns) than those with upper lobe disease and were less likely to have a decline in FVC over time. Percentage of lung volume affected by reticulation correlated with DLCO (R2=0.6218) Conclusion: The pattern of interstitial fibrosis is variable in myositis-related ILD. Lower zone predominant disease is more common but is not associated with worse prognosis. The proportion of reticulation appears to correlate with DLCO. Notably honeycombing does not but is an uncommon feature.

BACKGROUND AND OBJECTIVE:There is increasing interest in the role of lipids in processes that modulate lung fibrosis with evidence of lipid deposition in idiopathic pulmonary fibrosis (IPF) histological specimens. The aim of this study was to identify measurable markers of pulmonary lipid that may have utility as IPF biomarkers. STUDY DESIGN AND METHODS:IPF and control lung biopsy specimens were analysed using a unbiased lipidomic approach. Pulmonary fat attenuation volume (PFAV) was assessed on chest CT images (CTPFAV ) with 3D semi-automated lung density software. Aerated lung was semi-automatically segmented and CTPFAV calculated using a Hounsfield-unit (-40 to -200HU) threshold range expressed as a percentage of total lung volume. CTPFAV was compared to pulmonary function, serum lipids and qualitative CT fibrosis scores. RESULTS:There was a significant increase in total lipid content on histological analysis of IPF lung tissue (23.16 nmol/mg) compared to controls (18.66 mol/mg, p = 0.0317). The median CTPFAV in IPF was higher than controls (1.34% vs. 0.72%, p < 0.001) and CTPFAV correlated significantly with DLCO% predicted (R2 = 0.356, p < 0.0001) and FVC% predicted (R2 = 0.407, p < 0.0001) in patients with IPF. CTPFAV correlated with CT features of fibrosis; higher CTPFAV was associated with >10% reticulation (1.6% vs. 0.94%, p = 0.0017) and >10% honeycombing (1.87% vs. 1.12%, p = 0.0003). CTPFAV showed no correlation with serum lipids. CONCLUSION:CTPFAV is an easily quantifiable non-invasive measure of pulmonary lipids. In this pilot study, CTPFAV correlates with pulmonary function and radiological features of IPF and could function as a potential biomarker for IPF disease severity assessment.

This case describes a woman in her 50s who presented with recurrent lower respiratory tract infections. She was an ex-smoker and had worked on a livestock farm for many years. Chest radiograph and CT of the chest revealed multiple bilateral pulmonary nodules. Bronchoalveolar lavage and transbronchial biopsy did not confirm a unifying diagnosis and thus, surgical biopsy was pursued. Video-assisted thoracoscopic surgical guided biopsy of the right upper, middle and lower lobes demonstrated intraparenchymal minute nodules, consisting of bland epithelioid cells without any evidence of malignancy. The nodules stained positive for neural cell adhesion molecule (CD56) and progesterone receptor with weakly positive epithelial membrane antigen and smooth muscle actin. The combination of this characteristic staining pattern, the diffuse subcentimetre nature of the nodules and this clinical presentation fit with a diagnosis of the ultra-rare pulmonary disease, diffuse pulmonary meningotheliomatosis (DPM). This case highlights a rare cause of bilateral diffuse pulmonary nodules and thus, the breadth of differential diagnoses that need to be considered when approaching such a finding. Careful history-taking and thorough workup is often needed, typically requiring input from multiple specialties. DPM, while rare, should not be overlooked when considering the underlying cause of this presentation, especially in female patients. This case reiterates how common clinical presentations can unveil rare conditions and the contributions of physicians, pathologists and radiologists in the diagnosis and management of these complex diseases.

Rationale: Diffuse cystic lung diseases (DCLDs) represent a heterogeneous group of distinct pathophysiological entities that share a common phenotype of multiple thin-walled pulmonary cysts. Identifying DCLDs can result in earlier treatment, identification of malignancy, and family screening. A national referral centre for DCLDs was established in Ireland in 2019. The aim of this study was to describe the characteristics and clinical presentation of DCLDs. Methods: Data on all DCLD cases from 2019-2022 was collated. This included patient demographics, genetics, history of pneumothorax, biopsy results, pulmonary function tests and therapies. Lymphangioleiomyomatosis (LAM), Birt-Hogg-Dube syndrome (BHD), Lymphocytic Interstitial Pneumonia (LIP) and Pulmonary Langerhans Cell Histiocytosis (PLCH) comprised most patients. Groups were compared by ANOVA. Results: 109 patients with DCLD were included. The median age was 58 years old. 79% of patients were female and LAM was most common diagnosis (43%). 35% of patients had a history of pneumothorax with a significantly higher rate in BHD compared to other DCLDs (p=0.013) Significant variation existed across groups with lower baseline FEV1pp in PLCH and LAM compared to BHD and LIP (p=0.024). PLCH was associated with a lower DLCO at diagnosis (p=0.049). 31 patients underwent lung biopsy, indicating that improved diagnostic approaches negates the need for this in most patients. Conclusions: Our data indicates that despite their rarity, DCLDs share common features, yet differ in presentation and clinical course. With increased risk of malignancy and possible progressive disease, it is increasingly important to screen for these conditions.

Pulmonary alveolar proteinosis (PAP) is a syndrome characterized by the accumulation of pulmonary surfactant resulting in reduced oxygen uptake. It affects men, women, and children without predilection for socioeconomic status, geographic location, or race but occurs more commonly in smokers. Prevalence has been reported at 7–26 per million in the general population. Symptoms include dyspnea, cough, and fatigue. The clinical course includes progressive dyspnea, failure and, in some patients, serious secondary infections, pulmonary fibrosis, hypoxemic respiratory failure, and death. PAP is classified as primary (mediated by disruption of GM-CSF signaling), secondary (mediated by reduced alveolar macrophage functions due to an underlying clinical condition), or congenital (caused by mutations in genes involved in surfactant production). In primary PAP the most common cause is autoimmune PAP, which accounts for over 90% of all PAP syndrome. Pathogenesis is driven by impaired GM-CSF signaling to alveolar macrophages which require GM-CSF stimulation to stimulate surfactant clearance. The diagnosis of autoimmune PAP can be made by testing for an increased level of serum GM-CSF autoantibodies without a requirement for a lung biopsy. Whole-lung lavage is the main current treatment approach designed to remove excess surfactant by physically washing it out of the lungs but a pharmacotherapeutic approaches, inhaled GM-CSF is currently under evaluation.

The term "pulmonary renal syndrome" describes a clinical syndrome which is characterised by the presence of both diffuse alveolar haemorrhage and glomerulonephritis. It encompasses a group of diseases with distinctive clinical and radiological manifestations, as well as different pathophysiological processes. The most common diseases implicated are anti-neutrophil cytoplasm antibodies (ANCA)-positive small vessel vasculitis and anti-glomerular basement membrane (anti-GBM) disease. Prompt recognition is required as respiratory failure and end-stage renal failure can rapidly occur. Treatment includes a combination of glucocorticoids, immunosuppression, plasmapheresis and supportive measures. The use of targeted treatments has significantly reduced mortality. Thus, an understanding of pulmonary renal syndrome is essential for the respiratory physician.

Since commercial development in 2003, the usage of modern electronic cigarette (e-cigarette) continues to increase amongst people who have never smoked, ex-smokers who have switched to e-cigarettes, and dual-users of both conventional cigarettes and e-cigarettes. With such an increase in use, knowledge of the irritative, toxic and potential carcinogenic effects on the lungs is increasing. This review article will discuss the background of e-cigarettes, vaping devices and explore their popularity. We will further summarise the available literature describing the mechanism of lung injury caused by e-cigarette or vaping use.