Pulmonary alveolar proteinosis: from classification to therapy

Autoimmune pulmonary alveolar proteinosis presenting as localized multifocal GGOs: A case report

Pulmonary alveolar proteinosis (PAP) is a rare disease, which is characterized by the alveolar accumulation of surfactant. A crazy-paving appearance on chest thin-section computed tomography (TSCT) is a characteristic feature of this disease. We report an unusual case of PAP, which presented as multiple localized ground glass opacites (GGOs) on TSCT in an 80-year-old female. As one of these lesions at the apex of the right lung increased in size, it was suspected to be a pulmonary adenocarcinoma. However, the others became smaller during the follow-up period. Right upper lobectomy was performed, and PAP was histologically diagnosed. In cases exhibiting multiple localized GGOs, PAP should be considered, even if GGOs with a crazy-paving-like appearance are distributed in a lobular rather than diffuse manner.

Clinical approach for pulmonary alveolar proteinosis in children

In this editorial, we discuss the clinical implications of the article by Zhang et al. Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by excessive surfactant accumulation in the alveoli. It is classified into four categories: Primary, secondary, congenital, and unclassified forms. Primary PAP is caused by the disruption of granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor signaling, which is necessary for the clearance of surfactant by alveolar macrophages. It is further divided into autoimmune PAP, caused by anti-GM-CSF antibodies blocking alveolar macrophage activation, and hereditary PAP, resulting from mutations in genes encoding GM-CSF receptors. Secondary PAP develops due to conditions affecting the number or function of alveolar macrophages, such as infections, immunodeficiency, hematological disorders, or exposure to inhaled toxins. Congenital PAP is linked to mutations in genes involved in surfactant protein production. Notably, the causes of PAP differ between children and adults. Diagnostic features include a characteristic "crazy-paving" pattern on high-resolution computed tomography, accompanied by diffuse ground-glass opacities and interlobular septal thickening. The presence of PAP can be identified by the milky appearance of bronchoalveolar lavage fluid and histological evaluation. However, these methods cannot definitively determine the cause of PAP. Whole lung lavage remains the standard treatment, often combined with specific therapies based on the underlying cause.

Pulmonary alveolar proteinosis: presentation, diagnostic challenges, and management

Pulmonary alveolar proteinosis is a rare diffuse lung disease; diagnosis and treatment of which is often delayed. We present the case study of a 43-year-old male with a six-month history of worsening breathlessness and non-productive cough referred for specialist respiratory input. Rapid investigations, including high-resolution computed tomography (HRCT) and bronchoalveolar lavage, confirmed the diagnosis of pulmonary alveolar proteinosis. Treatment with whole lung lavage significantly improved pulmonary function and quality of life. We discuss the diagnosis and management of this condition and highlight the importance of early recognition and multidisciplinary teamwork in managing pulmonary alveolar proteinosis.

A Comprehensive Outlook on Pulmonary Alveolar Proteinosis-A Review

Pulmonary alveolar proteinosis (PAP) is an ultra-rare disease caused by impaired pulmonary surfactant clearance due to the dysfunction of alveolar macrophages or their signaling pathways. PAP is categorized into autoimmune, congenital, and secondary PAP, with autoimmune PAP being the most prevalent. This article aims to present a comprehensive review of PAP classification, pathogenesis, clinical presentation, diagnostics, and treatment. The literature search was conducted using the PubMed database and a total of 67 articles were selected. The PAP diagnosis is usually based on clinical symptoms, radiological imaging, and bronchoalveolar lavage, with additional GM-CSF antibody tests. The gold standard for PAP treatment is whole-lung lavage. This review presents a summary of the most recent findings concerning pulmonary alveolar proteinosis, pointing out specific features that require further investigation.

[Congenital pulmonary alveolar proteinosis in a neonate]

The male patient was referred to the hospital at 44 days old due to dyspnea after birth and inability to wean off oxygen. His brother died three days after birth due to respiratory failure. The main symptoms observed were respiratory failure, dyspnea, and hypoxemia. A chest CT scan revealed characteristic reduced opacity in both lungs with a "crazy-paving" appearance. The bronchoalveolar lavage fluid (BALF) showed periodic acid-Schiff positive proteinaceous deposits. Genetic testing indicated a compound heterozygous mutation in the ABCA3 gene. The diagnosis for the infant was congenital pulmonary alveolar proteinosis (PAP). Congenital PAP is a significant cause of challenging-to-treat respiratory failure in full-term infants. Therefore, congenital PAP should be considered in infants experiencing persistently difficult-to-treat dyspnea shortly after birth. Early utilization of chest CT scans, BALF pathological examination, and genetic testing may aid in early diagnosis.

A complicated case of whole-lung lavage: a case report

Introduction

We report a life-threatening case of severe respiratory failure due to a pulmonary alveolar proteinosis (PAP) secondary to lysinuric protein intolerance (LPI), complicated by a pre-existing right pneumothorax, which we treated using a rescue whole-lung lavage (WLL). To date, in the literature, there are no cases of WLL performed in this condition.

Clinical condition

Patient was referred to our center because of rapidly worsening dyspnea and deterioration of gas exchange, caused by a secondary form of PAP which required an immediate therapeutic option such as the one offered by WLL. On physical examination, bilateral crackles were present, and peripheral blood oxygen saturation was 78% on oxygen with a FiO2 of 40%.

Interventions

After stabilizing the clinical conditions with oxygen therapy erogated through a high-flow nasal cannula, shortly after admission, we performed a rescue WLL among two procedures. The procedure was very effective, and the patient was later discharged without oxygen therapy and in good clinical condition.

Conclusion

Our case report represents a chance to help fill the gap of knowledge relative to secondary forms of PAP. The patient we presented suffers from a very rare genetic condition (LPI) that only has a few reported cases in the literature and has a very low prevalence which makes it difficult to produce the affected people:newborns ratio. We believe that difficult and rare cases like this one can improve our understanding of the disease and, most importantly, of how much the only therapeutic option we had, a rescue WLL, is effective to improve gas exchange and radiological features, despite being performed in these severe respiratory conditions.

Unexpected diffuse lung lesions in a patient with pulmonary alveolar proteinosis: A case report

BACKGROUND

Pulmonary alveolar proteinosis (PAP) often presents nonspecifically and can be easily confused with: (1) Idiopathic interstitial lung fibrosis; (2) alveolar carcinoma; (3) pulmonary tuberculosis; and (4) other lung diseases such as viral pneumonia, mycoplasma pneumonia, and chlamydial pneumonia.

CASE SUMMARY

Diagnosis: In this case, a patient was diagnosed with PAP through transbronchial cryobiopsy (TBCB) and quantitative metagenomic next-generation sequencing, which confirmed the impairment of surfactant turnover as the underlying cause of PAP. Interventions: High-volume total lung lavage was performed for this patient. Outcomes: The patient's clinical condition had improved significantly by the 6-month follow-up, with a 92% finger oxygen saturation. A repeat chest computed tomography scan revealed scattered patchy ground-glass shadows in both lungs, which was consistent with alveolar protein deposition but with a lower density than in the radiograph from October 23, 2022.

CONCLUSION

TBCB has unique advantages in diagnosing atypical alveolar protein deposition, particularly for enabling the early detection of PAP. This information can help patients take preventive measures to prevent or halt PAP development by avoiding dusty environments and seeking treatment with total lung lavage and inhaled granulocyte macrophage colony-stimulating factor.

Alveolar macrophages in pulmonary alveolar proteinosis: origin, function, and therapeutic strategies

Pulmonary alveolar proteinosis (PAP) is a rare pulmonary disorder that is characterized by the abnormal accumulation of surfactant within the alveoli. Alveolar macrophages (AMs) have been identified as playing a pivotal role in the pathogenesis of PAP. In most of PAP cases, the disease is triggered by impaired cholesterol clearance in AMs that depend on granulocyte-macrophage colony-stimulating factor (GM-CSF), resulting in defective alveolar surfactant clearance and disruption of pulmonary homeostasis. Currently, novel pathogenesis-based therapies are being developed that target the GM-CSF signaling, cholesterol homeostasis, and immune modulation of AMs. In this review, we summarize the origin and functional role of AMs in PAP, as well as the latest therapeutic strategies aimed at addressing this disease. Our goal is to provide new perspectives and insights into the pathogenesis of PAP, and thereby identify promising new treatments for this disease.

CD40LG-associated X-linked Hyper-IgM Syndrome (XHIGM) with pulmonary alveolar proteinosis: a case report

BACKGROUND

D40LG-associated X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis has rarely been reported, and its genotype-phenotypic correlation remains elusive.

CASE PRESENTATION

We describe a five-month-old boy with CD40LG mutation (c.516T > A, p.Tyr172Ter) X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis as the first manifestation. The patient completely recovered after immunotherapy and allogeneic hematopoietic stem cell transplantation. In addition, four previously reported patients with CD40LG mutation with pulmonary alveolar proteinosis were also analyzed. All of these patients presented with early onset of pulmonary infections and a good response to immunotherapy. The structural model of CD40LG indicated that all mutations caused the X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis to be located within the tumor necrosis factor homology domain.

CONCLUSIONS

A case was presented, and the characteristics of four cases of CD40LG-associated X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis were summarized. The variant locations may explain the phenotypic heterogeneity of patients with the CD40LG mutation.

A Case of Pulmonary Alveolar Proteinosis in a 15-Year-Old Female Patient

Pulmonary alveolar proteinosis (PAP) is an extremely rare pulmonary disease that can be classified into primary, secondary, or congenital types. It typically presents with a pattern of interstitial lung disease. This rare condition is even rare in the adolescent or pediatric age group, making this case particularly rare and interesting. We report a case of a 15-year-old girl who presented with a four-month history of dry cough and exertional dyspnea. After performing a high-resolution computed tomography (HRCT) scan and bronchoalveolar lavage (BAL) with analysis of the BAL fluid, she was eventually diagnosed with PAP. She was then referred to a higher qualified center, where a whole lung lavage (WLL) was performed, resulting in significant improvement of her symptoms.

Updated severity and prognosis score of pulmonary alveolar proteinosis: A multi-center cohort study in China

Background

The high-resolution computed tomography (HRCT) score is an important component of the severity and prognosis score of pulmonary alveolar proteinosis (SPSP). However, the HRCT score in SPSP only considers the extent of opacity, which is insufficient.

Methods

We retrospectively evaluated HRCT scores for 231 patients with autoimmune pulmonary alveolar proteinosis (APAP) from three centers of the China Alliance for Rare Diseases. The SPSPII was created based on the overall density and extent, incorporating the SPSP. The severity of APAP patients was assessed using disease severity scores (DSS), SPSP, and SPSPII to determine the strengths and weaknesses of the different assessment methods. We then prospectively applied the SPSPII to patients before treatment, and the curative effect was assessed after 3 months.

Results

The HRCT overall density and extent scores in our retrospective analysis were higher than the extent scores in all patients and every original extent score severity group, as well as higher related to arterial partial oxygen pressure (PaO₂) than extent scores. The mild patients accounted for 61.9% based on DSS 1-2, 20.3% based on SPSP 1-3, and 20.8% based on SPSPII 1-3. Based on SPSP or SPSPII, the number of severe patients deteriorating was higher in the mild and moderate groups. When applied prospectively, arterial PaO₂ differed between any two SPSPII severity groups. The alveolar-arterial gradient in PaO₂ (P[A-a]O₂), % predicted carbon monoxide diffusing capacity of the lung (DLCO), and HRCT score were higher in the severe group than in the mild and moderate groups. After diagnosis, mild patients received symptomatic treatment, moderate patients received pure whole lung lavage (WLL) or granulocyte-macrophage colony-stimulating factor (GM-CSF) therapy, and severe patients received WLL and GM-CSF therapy. Importantly, the SPSPII in mild and severe groups were lower than baseline after 3 months.

Conclusion

The HRCT density and extent scores of patients with APAP were better than the extent score. The SPSPII score system based on smoking status, symptoms, PaO₂, predicted DLCO, and overall HRCT score was better than DSS and SPSP for assessing the severity and efficacy and predicting the prognosis.

Trial registration

ClinicalTrial.gov, identifier: NCT04516577.

Recombinant GM-CSF for diseases of GM-CSF insufficiency: Correcting dysfunctional mononuclear phagocyte disorders

Introduction

Endogenous granulocyte-macrophage colony-stimulating factor (GM-CSF), identified by its ability to support differentiation of hematopoietic cells into several types of myeloid cells, is now known to support maturation and maintain the metabolic capacity of mononuclear phagocytes including monocytes, macrophages, and dendritic cells. These cells sense and attack potential pathogens, present antigens to adaptive immune cells, and recruit other immune cells. Recombinant human (rhu) GM-CSF (e.g., sargramostim [glycosylated, yeast-derived rhu GM-CSF]) has immune modulating properties and can restore the normal function of mononuclear phagocytes rendered dysfunctional by deficient or insufficient endogenous GM-CSF.

Methods

We reviewed the emerging biologic and cellular effects of GM-CSF. Experts in clinical disease areas caused by deficient or insufficient endogenous GM-CSF examined the role of GM-CSF in mononuclear phagocyte disorders including autoimmune pulmonary alveolar proteinosis (aPAP), diverse infections (including COVID-19), wound healing, and anti-cancer immune checkpoint inhibitor therapy.

Results

We discuss emerging data for GM-CSF biology including the positive effects on mitochondrial function and cell metabolism, augmentation of phagocytosis and efferocytosis, and immune cell modulation. We further address how giving exogenous rhu GM-CSF may control or treat mononuclear phagocyte dysfunction disorders caused or exacerbated by GM-CSF deficiency or insufficiency. We discuss how rhu GM-CSF may augment the anti-cancer effects of immune checkpoint inhibitor immunotherapy as well as ameliorate immune-related adverse events.

Discussion

We identify research gaps, opportunities, and the concept that rhu GM-CSF, by supporting and restoring the metabolic capacity and function of mononuclear phagocytes, can have significant therapeutic effects. rhu GM-CSF (e.g., sargramostim) might ameliorate multiple diseases of GM-CSF deficiency or insufficiency and address a high unmet medical need.

GM-CSF antibodies in artificial stone associated silicoproteinosis: A case report and literature review

Pulmonary alveolar proteinosis (PAP) is a rare lung disease where there is accumulation of surfactant in the alveoli. It can be classified based on the underlying aetiology into three categories: primary, secondary and congenital. Autoantibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF-Ab) are a key diagnostic feature of autoimmune PAP. High intensity occupational exposure and inhalation of toxic particles such as silica can cause a form of secondary PAP called acute silicoproteinosis. We describe a 26-year-old stone benchtop fabricator with silicoproteinosis following daily exposure to high levels of silica who had elevated serum GM-CSF-Ab. We discuss the role of GM-CSF-Ab in cases of PAP with occupational inhalational exposure and the challenges in its interpretation.

Complete remission of pulmonary alveolar proteinosis after anti-tuberculous chemotherapy: a case report

Pulmonary alveolar proteinosis (PAP) is a rare respiratory system disorder. Patients with PAP are at risk for a wide variety of secondary infections. This current case report describes a patient with PAP complicated by tuberculosis. A 48-year-old male patient with multiple follow-up chest computed tomography scans that showed predominant diffuse ground glass opacity in both lung fields, presented a few years later with new calcified lesions and pleural effusion. At this point, the associated auxiliary examination indicated the possibility of PAP combined with tuberculosis infection. The patient achieved complete remission after anti-tuberculosis treatment. PAP is an easily overlooked clinical syndrome due to its low prevalence and lack of specific clinical manifestations, especially when combined with other pulmonary lesions. Therefore, clinicians should consider this rare disease in patients presenting with pulmonary disease and plan for its co-morbidity with other secondary outcomes, such as opportunistic infections, which are a common and life-threatening complication in patients with PAP. This case indicates the possibility that anti-tuberculosis therapy can improve alveolar proteinosis in patients with PAP and secondary Mycobacterium tuberculosis infection.

Opportunistic Infection Associated with Elevated GM-CSF Autoantibodies: A Case Series and Review of the Literature

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to play a key role in enhancing multiple immune functions that affect response to infectious pathogens including antigen presentation, complement- and antibody-mediated phagocytosis, microbicidal activity, and neutrophil chemotaxis. Reduced GM-CSF activity and immune response provides a mechanism for increased infection risk associated with autoimmune pulmonary alveolar proteinosis (aPAP) and other disorders involving the presence of GM-CSF autoantibodies. We present a case series of five patients with persistent or unusual pulmonary and central nervous system opportunistic infections (Cryptococcus gattii, Flavobacterium, Nocardia) and elevated GM-CSF autoantibody levels, as well as 27 cases identified on systematic review of the literature.

A mini-whole lung lavage to treat autoimmune pulmonary alveolar proteinosis (PAP)

Background

PAP is an ultra-rare respiratory syndrome characterized by the accumulation of surfactant within the alveoli. Whole lung lavage (WLL) is the current standard of care of PAP, however it is not a standardized procedure and the total amount of fluid used to wash each lung is still debated. Considering ICU hospitalization associated risks, a “mini-WLL” with anticipated manual clapping and reduced total infusion volume and has been proposed in our center.

The aim of the study is to retrospectively analyze the efficacy of mini-WLL compared to standard WLL at the Pavia center.

Methods

13 autoimmune PAP patients eligible for WLL were included: 7 patients were admitted to mini-WLL (9 L total infusion volume for each lung) and 6 patients underwent standard WLL (14 L of infusion volume). Functional data (VC%, FVC%, TLC%, DLCO%) and alveolar-arterial gradient values (A-aO2) were collected at the baseline and 1, 3, 6, 12, 18 months after the procedure.

Results

A statistically significant improvement of VC% (p = 0.013, 95%CI 3.49–30.19), FVC% (p = 0.016, 95%CI 3.37–32.09), TLC% (p = 0.001, 95%CI 7.38–30.34) was observed in the mini-WLL group in comparison with the standard WLL group, while no significant difference in DLCO% and A-aO2 mean values were reported.

Conclusion

Mini-WLL has demonstrated higher efficacy in ameliorating lung volumes, suggesting that a lower infusion volume is sufficient to remove the surfactant accumulation and possibly allows a reduced mechanical insult of the bronchi walls and the alveoli. However, no statistically significant differences were found in terms of DLCO% and Aa-O2.

CYFRA21-1 is a more sensitive biomarker to assess the severity of pulmonary alveolar proteinosis

Background

Serum lactate dehydrogenase (LDH), carcinoembryonic antigen (CEA) and CYFRA21-1 are the commonly used biomarkers to identify patients with autoimmune pulmonary alveolar proteinosis (APAP). However, it is not clear which of the biomarkers is more sensitive to the severity of the patient’s condition.

Methods

APAP patients numbering 151 were enrolled in this study. All patients’ severity was assessed through the severity and prognosis score of PAP (SPSP). According to the respective laboratory upper limits of serum levels of LDH, CEA and CYFRA21-1, APAP patients were divided into higher and lower-level groups. Patients were divided into five groups based on SPSP. 88 patients had completed six months of follow-up. We calculated sensitivity, specificity, and critical point of LDH, CEA and CYFRA21-1 between APAP patients and normal control group, and between grade 1–2 and 3–5 through receiving operating characteristics (ROC) curve.

Results

Serum LDH, CEA and CYFRA21-1 levels of patients with PAP were higher and distinctly related to PaO₂, FVC, FEV₁, DLCO, HRCT scores and SPSP. The SPSP of patients in higher-level LDH, CEA and CYFRA21-1 groups were higher than those of corresponding lower-level groups. Based on SPSP results, the patients were divided into five groups (grade I, 20; grade II, 37; grade III, 40; grade IV, 38; grade V, 16). The serum level of CYFRA21-1 of patients with APAP in grade II was higher than that of patients in grade I and lower than that of patients in grade III. Serum CYFRA21-1 of patients with APAP after six months were higher than the baseline among the aggravated group. Serum LDH, CEA and CYFRA21-1 levels after six months among patients in the relieved group of patients with APAP were lower than the baseline. ROC correlating LDH, CEA and CYFRA21-1 values with APAP severity (between grade 1–2 and 3–5) showed an optimal cutoff of LDH of over 203 U/L (< 246 U/L), CEA of over 2.56 ug/L (< 10 ug/L), and CYFRA21-1 of over 5.57 ng/ml (> 3.3 ng/ml) (AUC: 0.815, 95% CI [0.748–0.882], sensitivity: 0.606, specificity: 0.877).

Conclusion

Serum CYFRA21-1 level was more sensitive in revealing the severity of APAP than LDH and CEA levels among mild to moderate forms of disease.

Pulmonary storage

Interstitial lung diseases (ILDs) are not just a matter of scarring or inflammation in the lung tissue. The lungs can also serve as a repository for products that can be produced in excessive amounts in the human body as a result of disease. Geneticaly based dysfunctions of lysosomal enzymes, which leads to an unefficient degradation and transport of various macromolecules from lysosomes, are considered to be storage diseases sensu stricto. ILDs were described in patients with Gaucher disease, Niemann-Pick disease and Fabry disease. In a broader context, however, the accumulation of various substances in the lung tissue is also encountered in cases of pediatric pulmonary interstitial glycogenosis (PIG), alveolar lipoproteinosis or pulmonary amyloidosis. The cause of PIG is not clear. The disease was first described in 2002 and a lung tissue sample is required to establish this diagnosis. Even though PIG usually goes well in childhood and the patients difficulties spontaneously subside over time, the long-term prognosis of the patients is unknown. Alveolar lipoproteinoses can be acquired (e.g. after massive exposure to silica dust), autoimmune, but also genetically determined. Unlike lysosomal storage diseases, in the case of pulmonary alveolar lipoproteinosis, accumulation of abnormal macromolecules occurs only in the lungs of affected individuals. Similarly, amyloidosis is not a single disease, but a group of diseases with different etiopathogenesis, as a result of which amyloid - a group of different proteins with a distinctvive conformation, which can be deposited in various organs, including the lungs - is formed. The diagnosis of pulmonary alveolar lipoproteinosis is based on the typical appearance and biochemical composition of the fluid obtained by bronchoalveolar lavage, the diagnosis of amyloidosis is histological.

Revisiting the role of pulmonary surfactant in chronic inflammatory lung diseases and environmental exposure

Pulmonary surfactant is a crucial and dynamic lung structure whose primary functions are to reduce alveolar surface tension and facilitate breathing. Though disruptions in surfactant homeostasis are typically thought of in the context of respiratory distress and premature infants, many lung diseases have been noted to have significant surfactant abnormalities. Nevertheless, preclinical and clinical studies of pulmonary disease too often overlook the potential contribution of surfactant alterations - whether in quantity, quality or composition - to disease pathogenesis and symptoms. In inflammatory lung diseases, whether these changes are cause or consequence remains a subject of debate. This review will outline 1) the importance of pulmonary surfactant in the maintenance of respiratory health, 2) the diseases associated with primary surfactant dysregulation, 3) the surfactant abnormalities observed in inflammatory pulmonary diseases and, finally, 4) the available research on the interplay between surfactant homeostasis and smoking-associated lung disease. From these published studies, we posit that changes in surfactant integrity and composition contribute more considerably to chronic inflammatory pulmonary diseases and that more work is required to determine the mechanisms underlying these alterations and their potential treatability.

The Role of GM-CSF Autoantibodies in Infection and Autoimmune Pulmonary Alveolar Proteinosis: A Concise Review

Autoantibodies to multiple cytokines have been identified and some, including antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), have been associated with increased susceptibility to infection. High levels of GM-CSF autoantibodies that neutralize signaling cause autoimmune pulmonary alveolar proteinosis (aPAP), an ultrarare autoimmune disease characterized by accumulation of excess surfactant in the alveoli, leading to pulmonary insufficiency. Defective GM-CSF signaling leads to functional deficits in multiple cell types, including macrophages and neutrophils, with impaired phagocytosis and host immune responses against pulmonary and systemic infections. In this article, we review the role of GM-CSF in aPAP pathogenesis and pulmonary homeostasis along with the increased incidence of infections (particularly opportunistic infections). Therefore, recombinant human GM-CSF products may have potential for treatment of aPAP and possibly other infectious and pulmonary diseases due to its pleotropic immunomodulatory actions.

Selection Criteria for Lung Transplantation: Controversies and New Developments

Lung transplantation is an accepted therapeutic option for end-stage lung diseases. The imbalance between limited availability and vast need of donor organs necessitates careful selection of recipient candidates, ensuring the best possible utilization of the scarce resource of organs. Nonetheless, possible lung transplant candidates who could experience a meaningful improvement in survival and quality of life should not be excluded solely based on the complexity of their case. In this review, controversial issues or difficult limitations for lung transplantation, and new developments in recipient selection criteria, are discussed, which may help broaden recipient eligibility for lung transplantation without compromising long-term outcomes.