Rituximab for auto-immune alveolar proteinosis, a real life cohort study

Pulmonary alveolar proteinosis following severe COVID - 19 infection: A case report

A 67-year-old male, with a history of severe COVID-19 infection and exposure to talc was seen for worsening shortness of breath for months, requiring supplemental oxygen. He was treated for COVID-19 infection and suspected pneumonia with no improvement. His pulmonary function test (PFT) worsened and computed tomography (CT) showing bilateral airspace opacities with ground-glass opacities (GGO), also worsened over time. He underwent bronchoscopy, bronchoalveolar lavage and pathology revealed pulmonary alveolar proteinosis (PAP). He subsequently underwent whole lung lavage (WLL) which significantly improved his crazy paving pattern on CT and was successfully weaned off supplemental oxygen.

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.

The world of rare interstitial lung diseases

The world of rare interstitial lung diseases (ILDs) is diverse and complex. Diagnosis and therapy usually pose challenges. This review describes a selection of rare and ultrarare ILDs including pulmonary alveolar proteinosis, pulmonary alveolar microlithiasis and pleuroparenchymal fibroelastosis. In addition, monogenic ILDs or ILDs in congenital syndromes and various multiple cystic lung diseases will be discussed. All these conditions are part of the scope of the European Reference Network on rare respiratory diseases (ERN-LUNG). Epidemiology, pathogenesis, diagnostics and treatment of each disease are presented.

Alveolar Proteinosis in COVID-19: Clinical Case

Pulmonary alveolar proteinosis (PAP) is a rare, diffuse lung disease characterized by accumulation of lipoprotein in lung surfactant in the alveolar space and terminal bronchioles, leading to impaired gas exchange and arterial hypoxemia. We present the case of a 51-year-old woman who was admitted with a diagnosis of severe SARS-CoV-2 pneumonia. Her condition did not improve with corticosteroids. A chest CT scan revealed ground-glass opacities in all lung lobes, with septal thickening. A differential diagnosis was proposed with other diseases. Bronchoscopy revealed milky bronchoalveolar lavage fluid, and staining with periodic acid-Schiff was positive, thus indicating PAP. Therefore, the patient underwent whole lung lavage, which led to clinical, radiological, and functional improvement. In the context of the COVID-19 pandemic, differential diagnosis ensures that appropriate attention is given to less prevalent entities such as PAP.

Anti-cytokine autoantibodies and inborn errors of immunity

The past quarter of a century has witnessed an inordinate increase in our understanding of primary immunodeficiencies / inborn errors of immunity. These include a significant increase in the number of identified conditions, broadening the phenotypes of existing entities, delineation of classical inborn errors of immunity from those with a narrow phenotype, and a gradual shift from supportive to definitive care in patients afflicted with these diseases. It has also seen the discovery of conditions broadly defined as phenocopies of primary immunodeficiencies, where somatic mutations or autoantibodies mimic a recognised primary immunodeficiency's presentation in the absence of the underlying genetic basis for that disease. This article will provide a review of the anti-cytokine autoantibody-mediated phenocopies of inborn errors of immunity and discuss the therapeutic and laboratory aspects of this group of diseases.

Autoimmune Pulmonary Alveolar Proteinosis

Autoimmune pulmonary alveolar proteinosis (PAP) is a rare disease characterized by myeloid cell dysfunction, abnormal pulmonary surfactant accumulation, and innate immune deficiency. It has a prevalence of 7-10 per million; occurs in individuals of all races, geographic regions, sex, and socioeconomic status; and accounts for 90% of all patients with PAP syndrome. The most common presentation is dyspnea of insidious onset with or without cough, production of scant white and frothy sputum, and diffuse radiographic infiltrates in a previously healthy adult, but it can also occur in children as young as 3 years. Digital clubbing, fever, and hemoptysis are not typical, and the latter two indicate that intercurrent infection may be present. Low prevalence and nonspecific clinical, radiological, and laboratory findings commonly lead to misdiagnosis as pneumonia and substantially delay an accurate diagnosis. The clinical course, although variable, usually includes progressive hypoxemic respiratory insufficiency and, in some patients, secondary infections, pulmonary fibrosis, respiratory failure, and death. Two decades of research have raised autoimmune PAP from obscurity to a paradigm of molecular pathogenesis-based diagnostic and therapeutic development. Pathogenesis is driven by GM-CSF (granulocyte/macrophage colony-stimulating factor) autoantibodies, which are present at high concentrations in blood and tissues and form the basis of an accurate, commercially available diagnostic blood test with sensitivity and specificity of 100%. Although whole-lung lavage remains the first-line therapy, inhaled GM-CSF is a promising pharmacotherapeutic approach demonstrated in well-controlled trials to be safe, well tolerated, and efficacious. Research has established GM-CSF as a pulmonary regulatory molecule critical to surfactant homeostasis, alveolar stability, lung function, and host defense.

Rituximab rescue therapy for autoimmune pulmonary alveolar proteinosis

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare lung disease characterised by abnormal alveolar surfactant accumulation due to macrophage dysfunction. Whole lung lavage (WLL) is the cornerstone of first-line aPAP therapy, but effective rescue treatments have not yet been well established. We report a case of a 41-year-old man with aPAP in whom further WLL is contraindicated. His diagnosis was established using a combination of classical radiological findings, positive serum GM-CSF IgG antibodies and bronchoalveolar lavage (BAL) findings. Following a literature review of emerging therapies, a decision was made to treat with a course of rituximab to suppress GM-CSF autoantibody production and restore alveolar surfactant-macrophage homeostasis. A significant clinical response was demonstrated within 6 months with improvements in arterial oxygenation, respiratory membrane gas diffusion, six-minute walk test and radiological findings.

A Bibliometric Analysis of Pulmonary Alveolar Proteinosis From 2001 to 2021

Background

Pulmonary alveolar proteinosis (PAP) is a rare syndrome first described by Rosen et al. in 1958. Despite our considerably evolved understanding of PAP over the past decades, no bibliometric studies have been reported on this field. We aimed to analyze and visualize the research hotspots and current trends of the PAP research field using a bibliometric analysis to help understand the future development of basic and clinical research.

Methods

The literature regarding PAP was culled from the Web of Science Core Collection (WoSCC) database. Data were extracted from the relevant articles and visually analyzed using CiteSpace and VOSviewer software.

Results

Nine hundred and nine qualifying articles were included in the analysis. Publications regarding PAP increased over time. These articles mainly come from 407 institutions of 57 countries. The leading countries were the USA and Japan. University of Cincinnati (USA) and Niigata University (Japan) featured the highest number of publications among all institutions. Bruce C Trapnell exerts a significant publication impact and has made the most outstanding contributions in the field of PAP. American Journal of Physiology-Lung Cellular and Molecular Physiology was the journal with the most publications, and American Journal of Respiratory and Critical Care Medicine was the most commonly cited journal. All the top 5 co-cited journals belong to Q1. Keyword citation bursts revealed that inflammation, deficiency, tissue resident macrophage, classification, autoimmune pulmonary alveolar proteinosis, sarcoidosis, gm csf, high resolution ct, and fetal monocyte were the emerging research hotspots.

Conclusion

Research on PAP is prosperous. International cooperation is also expected to deepen and strengthen in the future. Our results indicated that the etiology and pathogenesis of PAP, current and emerging therapies, especially the novel pathogenesis-based options will remain research hotspots in the future.

Anticytokine autoantibodies: Autoimmunity trespassing on antimicrobial immunity

Anticytokine autoantibodies can cause immunodeficiency or dysregulate immune responses. They may phenocopy genetically defined primary immunodeficiencies. We review current anti-type 1 and anti-type 2 interferon; anti-IL-12/23, anti-IL-17, and anti-GM-CSF autoantibodies; HLA associations; disease associations; and mechanistically based treatment options. Suspecting the presence of these autoantibodies in patients and identifying them at the onset of symptoms should ameliorate disease and improve outcomes.

Update on Diagnosis and Treatment of Adult Pulmonary Alveolar Proteinosis

Pulmonary alveolar proteinosis (PAP) is a rare pulmonary surfactant homeostasis disorder resulting in buildup of lipo-proteinaceous material within the alveoli. PAP is classified as primary (autoimmune and hereditary), secondary, congenital and unclassifiable type based on the underlying pathogenesis. PAP has an insidious onset and can, in some cases, progress to severe respiratory failure. Diagnosis is often secured with bronchoalveolar lavage in the setting of classic imaging findings. Recent insights into genetic alterations and autoimmune mechanisms have provided newer diagnostics and treatment options. In this review, we discuss the etiopathogenesis, diagnosis and treatment options available and emerging for PAP.

Autoimmune pulmonary alveolar proteinosis successfully treated with lung lavage in an adolescent patient: a case report

Background

Pulmonary alveolar proteinosis is a rare interstitial lung disease characterized by accumulating surfactant materials in the alveoli. The autoimmune form is by far the most common in adults, while in the pediatric age group, the vast majority of cases are congenital. We report a case of an adolescent patient diagnosed with autoimmune pulmonary alveolar proteinosis, which is unusual in this age group.

Case presentation

A-15 year-old Saudi male presented to the emergency department with a history of shortness of breath and low oxygen saturation. High-resolution computed tomography of his chest showed a global crazy-paving pattern. Autoantibodies against granulocyte-macrophage colony-stimulating factor were detected in his serum. A diagnosis of the autoimmune form of pulmonary alveolar proteinosis was confirmed after excluding other possible causes. The patient improved after he underwent whole lung lavage under general anesthesia, and he was independent of oxygen therapy after 6 months of follow-up.

Conclusion

The autoimmune form of pulmonary alveolar proteinosis is rare in the pediatric age group and should be considered when no apparent cause of this disease was found. Whole lung lavage should be the first treatment modality offered in this setting with close follow-up and monitoring.

Long-term follow-up and successful treatment of pulmonary alveolar proteinosis without hypercholesterolemia with statin therapy: a case report

Pulmonary alveolar proteinosis (PAP) is a rare disorder characterized by the accumulation of excessive surfactant lipids and proteins in alveolar macrophages and alveoli. Oral statin therapy is a novel treatment for PAP with hypercholesterolemia. However, this treatment has never been described in a patient without hypercholesterolemia. Here, we present a case of successful treatment with atorvastatin for a patient with possibly unclassified PAP without hypercholesterolemia who responded poorly to whole lung lavage therapy and inhaled granulocyte-macrophage colony-stimulating factor. After 18 months of atorvastatin treatment, the patient experienced improvements in dyspnea, radiographic abnormalities and pulmonary function. The present case study supports the feasibility of statin therapy for PAP regardless of the level of cholesterol.

Mild dyspnea presenting as 'crazy-paving' on chest computed tomography

Pulmonary alveolar proteinoisis (PAP) is a rare disease characterized by accumulation of proteinaceous material in the alveolar spaces. Here, we report a case of mild dyspnea with incidental ‘crazy-paving’ pattern on chest computed tomography (CT). Further evaluation and bronchoscopy found to have PAP.

Granulocyte Macrophage Colony-Stimulating Factor-Specific Autoantibodies and Cerebral Nocardia With Pulmonary Alveolar Proteinosis

In this study, we report the history of a 40-year-old man with a primary cerebral abscess caused by Nocardia abscessus that led to the discovery of autoimmune pulmonary alveolar lipoproteinosis (anti-granulocyte-macrophage colony-stimulating factor [GM-CSF] autoantibodies). Anti-GM-CSF autoantibodies promote immunodeficiency and should be monitored to prevent opportunistic and disseminated infections and to diagnose asymptomatic pulmonary alveolar lipoproteinosis.

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.

Pulmonary alveolar proteinosis

PAP is an ultra-rare disease in which surfactant components, that impair gas exchange, accumulate in the alveolae. There are three types of PAP. The most frequent form, primary PAP, includes autoimmune PAP which accounts for over 90% of all PAP, defined by the presence of circulating anti-GM-CSF antibodies. Secondary PAP is mainly due to haematological disease, infections or inhaling toxic substances, while genetic PAP affects almost exclusively children. PAP is suspected if investigation for ILD reveals a crazy-paving pattern on chest CT scan, and is confirmed by a milky looking BAL that gives a positive PAS reaction indicating extracellular proteinaceous material. PAP is now rarely confirmed by surgical lung biopsy. WLL is still the first-line treatment, with an inhaled GM-CSF as second-line treatment. Inhalation has been found to be better than subcutaneous injections. Other treatments, such as rituximab or plasmapheresis, seem to be less efficient or ineffective. The main complications of PAP are due to infections by standard pathogens (Streptococcus, Haemophilus and Enterobacteria) or opportunistic pathogens such as mycobacteria, Nocardia, Actinomyces, Aspergillus or Cryptococcus. The clinical course of PAP is unpredictable and spontaneous improvement can occur. The 5-year actuarial survival rate is 95%.

Valuable Serum Markers in Pulmonary Alveolar Proteinosis

Objective

Several serum markers were reported to reflect the severity of pulmonary alveolar proteinosis (PAP). The aim of this study is to investigate a reliable and facile marker to access and monitor the clinical course of PAP in a large cohort.

Methods

PAP patients from January 2010 to June 2018 were enrolled. Hospital records were used as data sources. The levels of various serum indicators were detected. We evaluated the correlation between pulmonary function test results and clinical variables.

Results

Diffusion capacity for carbon monoxide (DLCO) level was positively correlated with the level of high-density lipoprotein cholesterol (HDL-C) (P < 0.05) in 122 patients of PAP at baseline. The levels of HDL-C and DLCO significantly increased while carcinoembryonic antigen (CEA), CYFRA21-1, neuron-specific enolase (NSE), and lactic dehydrogenase (LDH) levels decreased six months after granulocyte-macrophage colony-stimulating factor (GM-CSF) inhalation therapy between 14 patients with PAP. Nevertheless, the increased DLCO was significantly correlated with decreased CEA (r = ‐0.579, P = 0.031) and CYFRA 21-1 (r = ‐0.632, P = 0.015). In 10 PAP patients without GM-CSF inhalation therapy, HDL-C and DLCO significantly decreased while NSE and LDH levels increased after six months of follow-up. The decreased DLCO was significantly correlated with increased LDH (r = ‐0.694, P = 0.026).

Conclusions

Serum CEA, CYFRA21-1, and LDH are valuable serum markers for the evaluation of disease activity of PAP and may predict the response to treatment of PAP.

Shaping the future of an ultra-rare disease: unmet needs in the diagnosis and treatment of pulmonary alveolar proteinosis

PURPOSE OF REVIEW

Pulmonary alveolar proteinosis (PAP) can be considered the archetype of ultra-rare diseases with a prevalence of under 10 cases per million. We discuss the classification of PAP, the current diagnostic practice and the supplementary role of genetic testing and granulocyte-macrophage colony-stimulating factor (GM-CSF) signalling in the diagnosis of congenital and hereditary PAP. We report on novel therapeutic approaches such as GM-CSF substitution, stem cell transplantation, pioglitazone, statins and immunomodulation.

RECENT FINDINGS

The discovery of new genetic mutations underlying this syndrome raises the question whether the classification should be radically revised in the future. Serum GM-CSF autoantibody is the best diagnostic marker for autoimmune PAP, the most common form, but does not correlate with disease severity. Several circulating biomarkers have been investigated to assess disease activity and predict outcome. Imaging techniques have also enormously evolved and offer new tools to quantify disease burden and possibly drive therapeutic decisions. Promising clinical trials are ongoing and will generate new treatment strategies besides or in addition to whole lung lavage in the next future.

SUMMARY

Despite impressive advances in understanding pathogenesis, PAP remains a rare syndrome with several unanswered questions impacting diagnosis, management and treatment, and, as a result, patients' quality of life.

Functional Analysis of Anti-cytokine Autoantibodies Using Flow Cytometry

Autoantibodies to cytokines are increasingly being detected in association with immunodeficient, autoimmune and immune dysregulated states. Presence of these autoantibodies in an otherwise healthy individual may result in a unique phenotype characterized by predisposition to infection with specific organisms. The ability to detect these autoantibodies is of importance as it may direct treatment toward a combination of anti-microbial agents and immunomodulatory therapies that decrease autoantibody levels, thereby releasing the immune system from autoantibody-mediated inhibition. Ligand binding assays such as ELISA or bead multiplex assays have been used to detect these antibodies. However, not all anti-cytokine autoantibodies have demonstrable function in vitro and therefore their clinical significance is unclear. Assays that evaluate the functionality of anti-cytokine autoantibodies can supplement such ligand binding assays and add valuable functional information that, when viewed in the context of the clinical phenotype, may guide the use of adjunctive immunomodulatory therapy. This mini review provides an overview of anti-cytokine autoantibodies identified to date and their clinical associations. It also describes the use of flow cytometry for the functional analysis of anti-IFNγ and anti-GM-CSF autoantibodies.

Pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a syndrome characterized by the accumulation of alveolar surfactant and dysfunction of alveolar macrophages. PAP results in progressive dyspnoea of insidious onset, hypoxaemic respiratory failure, secondary infections and pulmonary fibrosis. PAP can be classified into different types on the basis of the pathogenetic mechanism: primary PAP is characterized by the disruption of granulocyte-macrophage colony-stimulating factor (GM-CSF) signalling and can be autoimmune (caused by elevated levels of GM-CSF autoantibodies) or hereditary (due to mutations in CSF2RA or CSF2RB, encoding GM-CSF receptor subunits); secondary PAP results from various underlying conditions; and congenital PAP is caused by mutations in genes involved in surfactant production. In most patients, pathogenesis is driven by reduced GM-CSF-dependent cholesterol clearance in alveolar macrophages, which impairs alveolar surfactant clearance. PAP has a prevalence of at least 7 cases per million individuals in large population studies and affects men, women and children of all ages, ethnicities and geographical locations irrespective of socioeconomic status, although it is more-prevalent in smokers. Autoimmune PAP accounts for >90% of all cases. Management aims at improving symptoms and quality of life; whole-lung lavage effectively removes excessive surfactant. Novel pathogenesis-based therapies are in development, targeting GM-CSF signalling, immune modulation and cholesterol homeostasis.