Environmental Risk Factors for Sarcoidosis

Infectious and non-infectious precipitants of sarcoidosis

Sarcoidosis is a chronic inflammatory disease that can affect any organ in the body. Its exact cause remains unknown, but it is believed to result from a combination of genetic and environmental factors. Some potential causes of sarcoidosis include genetics, environmental triggers, immune system dysfunction, the gut microbiome, sex, and race/ethnicity. Genetic mutations are associated with protection against disease progression or an increased susceptibility to more severe disease, while exposure to certain chemicals, bacteria, viruses, or allergens can trigger the formation of immune cell congregations (granulomas) in different organs. Dysfunction of the immune system, including autoimmune reactions, may also contribute. The gut microbiome and factors such as being female or having African American, Scandinavian, Irish, or Puerto Rican heritage are additional contributors to disease outcome. Recent research has suggested that certain drugs, such as anti-Programmed Death-1 (PD-1) and antibiotics such as tuberculosis (TB) drugs, may raise the risk of developing sarcoidosis. Hormone levels, particularly higher levels of estrogen and progesterone in women, have also been linked to an increased likelihood of sarcoidosis. The diagnosis of sarcoidosis involves a comprehensive assessment that includes medical history, physical examination, laboratory tests, and imaging studies. While there is no cure for sarcoidosis, the symptoms can often be effectively managed through various treatment options. Treatment may involve the use of medications, surgical interventions, or lifestyle changes. These disparate factors suggests that sarcoidosis has multiple positive and negative exacerbants on disease severity, some of which can be ameliorated and others which cannot.

High-Risk Sarcoidosis: A Focus on Pulmonary, Cardiac, Hepatic and Renal Advanced Diseases, as Well as on Calcium Metabolism Abnormalities

Although sarcoidosis is generally regarded as a benign condition, approximately 20-30% of patients will develop a chronic and progressive disease. Advanced pulmonary fibrotic sarcoidosis and cardiac involvement are the main contributors to sarcoidosis morbidity and mortality, with failure of the liver and/or kidneys representing additional life-threatening situations. In this review, we discuss diagnosis and treatment of each of these complications and highlight how the integration of clinical, pathological and radiological features may help predict the development of such high-risk situations in sarcoid patients.

Dexamethasone alleviates pulmonary sarcoidosis by regulating the TGF-β/Smad3 signaling to promote Th17/Treg cell rebalance

Pulmonary sarcoidosis is an immune-mediated disorder closely related to Th17/Treg cell imbalance. Dexamethasone has been shown to regulate inflammation and immune responses in sarcoidosis patients. However, the underlying mechanisms of dexamethasone regulating Th17/Treg balance in sarcoidosis remain elusive. Herein, we elucidated the function role of TGF-β/Smad3 signaling in pulmonary sarcoidosis development and explored the underlying mechanism of dexamethasone in treating pulmonary sarcoidosis. We found that the TGF-β/Smad3 pathway was inactivated in pulmonary sarcoidosis patients. Propionibacterium acnes (PA) induced mouse model was generated to investigate the function of TGF-β/Smad3 signaling in vivo. Data indicated that IL17A inhibition with neutralizing antibody and activation of TGF-β/Smad3 signaling with SRI-011381 alleviated granuloma formation in the sarcoidosis mouse model. Moreover, we revealed that the Th17/Treg cell ratio was increased with PA treatment in mouse bronchoalveolar lavage fluid (BALF) and peripheral blood. The concentration of cytokines produced by Th17 cells (IL-17A, IL-23) was up-regulated in the BALF of PA-treated mice, while those produced by Tregs (IL-10, TGF-β1) presented significant reduction. The treatment of IL-17A neutralizing antibody or SRI-011381 was demonstrated to rescue the PA-induced changes in the concentration of IL-17A, IL-23, IL-10, and TGF-β1. Additionally, we demonstrated that dexamethasone treatment activated the TGF-β/Smad3 signaling in the lung tissues of pulmonary sarcoidosis mice. Dexamethasone was also revealed to promote the rebalancing of the Th17/Treg ratio and attenuated the granuloma formation in pulmonary sarcoidosis. In conclusion, dexamethasone activates the TGF-β/Smad3 signaling and induces Th17/Treg rebalance, alleviating pulmonary sarcoidosis, which suggests the potential of dexamethasone in treating pulmonary sarcoidosis.

Concurrent features of sarcoidosis and hypersensitivity pneumonitis in two patients exposed to fungal antigens

BACKGROUND

Sarcoidosis and hypersensitivity pneumonitis (HP) are two distinct clinical entities that share granulomatous inflammation, although each of them has specific clinical, radiologic and pathologic profiles. Coexistence of the two diseases have been described, suggesting, at least in some cases, a common biologic background.

CASE PRESENTATION

We describe two patients showing the concurrent diagnosis of sarcoidosis and hypersensitivity pneumonitis. Case 1: a 51-year old never smoker man had a history of occupational exposure, episodes of acute exacerbations and positive serum precipitins to Penicillium spp suggestive of HP, while the positivity of serum angiotensin converting enzyme (ACE) favored sarcoidosis. Case 2: a 42-year old non-smoker woman with occasional finding of enlarged mediastinal lymph nodes had a history of domestic exposure to molds and positive serum precipitins to Aspergillus spp suggestive of HP. In both cases high resolution computed tomography (HRCT) together with broncoscopy findings allowed to maintain both the diagnoses: HRCT showed both enlarged hilar/mediastinal limph nodes and intersitial lung involvement typical of HP; bronchoalveolar lavage presented marked lymphocytosis and granulomatous nodal lesions were observed at transbronchial needle aspiration.

CONCLUSIONS

Sarcoidosis and HP share some clinical findings and the differential diagnosis may be difficult. Our cases suggest that a common trait may be responsible for the concurrent diagnosis of sarcoidosis and hypersensitivity pneumonitis in the same patient.

FDG PET/CT and thyroid biopsy leads to neurosarcoidosis diagnosis

We present a unique case of neurosarcoidosis diagnosed based on thyroid biopsy and FDG PET (Fluorodeoxyglucose positron emission tomography) imaging. A patient presented for a second opinion after being placed in hospice for rapidly progressing dementia, presumed to be due to Creutzfeldt Jakob disease despite negative workup and was unable to perform activities of daily life or communicate with his wife. The patient underwent a workup including whole-body FDG PET, which showed hypermetabolic lymph nodes as well as a hypermetabolic nodule in the thyroid. Biopsy of the lymph nodes was nondiagnostic, but the thyroid biopsy tissue yielded a diagnosis of sarcoid. After ruling out other causes and reviewing the tissue pathology, the patient was diagnosed with systemic sarcoidosis with neurological involvement and started on infliximab with rapid improvement.

Exertional Dyspnea Incidentally Diagnosed as Sarcoidosis: A Teaching Hospital Experience

Background

Sarcoidosis is a complex disease with nonspecific etiology and clinical presentation. Its diagnosis is often delayed due to the absence of a single specific investigation modality. A multidisciplinary approach is necessary for its diagnosis. Report. A 49-year-old male presented with recurrent dyspnea on exertion, easy fatigue, and chest pain after several visits to different health facilities over 5 months. A diagnosis of pulmonary sarcoidosis was made after a series of laboratory and imaging investigations were done revealing bilateral reticonodular opacifications, noncaseating granulomata, elevated serum ACE and calcium levels consistent with sarcoidosis.

Conclusion

Sarcoidosis, although a rare presentation in our setting, may easily be overlooked or misdiagnosed if a holistic or multidisciplinary approach is not employed in its diagnosis. Nonspecificity of symptoms contributes to the delayed diagnosis.

Genetic and geographic influence on phenotypic variation in European sarcoidosis patients

Introduction

Sarcoidosis is a highly variable disease in terms of organ involvement, type of onset and course. Associations of genetic polymorphisms with sarcoidosis phenotypes have been observed and suggest genetic signatures.

Methods

After obtaining a positive vote of the competent ethics committee we genotyped 1909 patients of the deeply phenotyped Genetic-Phenotype Relationship in Sarcoidosis (GenPhenReSa) cohort of 31 European centers in 12 countries with 116 potentially disease-relevant single-nucleotide polymorphisms (SNPs). Using a meta-analysis, we investigated the association of relevant phenotypes (acute vs. sub-acute onset, phenotypes of organ involvement, specific organ involvements, and specific symptoms) with genetic markers. Subgroups were built on the basis of geographical, clinical and hospital provision considerations.

Results

In the meta-analysis of the full cohort, there was no significant genetic association with any considered phenotype after correcting for multiple testing. In the largest sub-cohort (Serbia), we confirmed the known association of acute onset with TNF and reported a new association of acute onset an HLA polymorphism. Multi-locus models with sets of three SNPs in different genes showed strong associations with the acute onset phenotype in Serbia and Lublin (Poland) demonstrating potential region-specific genetic links with clinical features, including recently described phenotypes of organ involvement.

Discussion

The observed associations between genetic variants and sarcoidosis phenotypes in subgroups suggest that gene-environment-interactions may influence the clinical phenotype. In addition, we show that two different sets of genetic variants are permissive for the same phenotype of acute disease only in two geographic subcohorts pointing to interactions of genetic signatures with different local environmental factors. Our results represent an important step towards understanding the genetic architecture of sarcoidosis.

Pulmonary Sarcoidosis: Experimental Models and Perspectives of Molecular Diagnostics Using Quantum Dots

Sarcoidosis is a complex inflammatory multisystem disease of unknown etiology that is characterised by epithelioid cell granulomatous lesions affecting various organs, mainly the lungs. In general, sarcoidosis is asymptomatic, but some cases result in severe complications and organ failure. So far, no accurate and validated modelling for clinical and pathohistological manifestations of sarcoidosis is suggested. Moreover, knowledge about disease-specific diagnostic markers for sarcoidosis is scarce. For instance, pulmonary granulomatosis is associated with the upregulated production of proinflammatory molecules: TNF-α, IL-6, CXCL1, CCL2, CCL18, CD163, serum angiotensin-converting enzyme (sACE), lysozyme, neopterin, and serum amyloid A (SAA). Quantum dots (QDs) are widely applied for molecular diagnostics of various diseases. QDs are semiconductor nanoparticles of a few nanometres in size, made from ZnS, CdS, ZnSe, etc., with unique physical and chemical properties that are useful for the labelling and detection in biological experiments. QDs can conjugate with various antibodies or oligonucleotides, allowing for high-sensitivity detection of various targets in organs and cells. Our review describes existing experimental models for sarcoidosis (in vitro, in vivo, and in silico), their advantages and restrictions, as well as the physical properties of quantum dots and their potential applications in the molecular diagnostics of sarcoidosis. The most promising experimental models include mice with TSC2 deletion and an in silico multiscale computational model of sarcoidosis (SarcoidSim), developed using transcriptomics and flow cytometry of human sarcoid biopsies. Both models are most efficient to test different candidate drugs for sarcoidosis.

A sarcoidosis patient developing psoriatic arthritis 18 years later: first description

.

Epidemiology of Sarcoidosis in U.S. Veterans from 2003 to 2019

Rationale: United States veterans represent an important population to study sarcoidosis. Their unique history of environmental exposures, wide geographic distribution, and long-term enrollment in a single integrated healthcare system provides an unparalleled opportunity to understand the incidence, prevalence, and risk factors for sarcoidosis. Objectives: To determine the epidemiology, patient characteristics, geographic distribution, and associated risk factors of sarcoidosis among U.S. veterans. Methods: We used data from the Veterans Health Administration (VHA) electronic health record system between 2003 and 2019 to evaluate the annual incidence, prevalence, and geographic distribution of sarcoidosis (defined using the International Classification of Diseases codes). We used multivariate logistic regression to examine patient characteristics associated with sarcoidosis incidence. Results: Among more than 13 million veterans who received care through or paid for by the VHA, 23,747 (0.20%) incident diagnoses of sarcoidosis were identified. Compared with selected VHA control subjects using propensity score matching, veterans with sarcoidosis were more likely to be female (13.5% vs. 9.0%), of Black race (52.2% vs. 17.0%), and ever-tobacco users (74.2% vs. 64.5%). There was an increase in the annual incidence of sarcoidosis between 2004 and 2019 (from 38 to 52 cases/100,000 person-years) and the annual prevalence between 2003 and 2019 (from 79 to 141 cases/100,000 persons). In a multivariate logistic regression model, Black race (odds ratio [OR], 4.49; 95% confidence interval [CI], 4.33-4.65), female sex (OR, 1.64; 95% CI, 1.56-1.73), living in the Northeast compared with the western region (OR, 1.57; 95% CI, 1.48-1.67), history of tobacco use (OR, 1.36; 95% CI, 1.31-1.41), and serving in the Army, Air Force, or multiple branches compared with the Navy (OR, 1.08; 95% CI, 1.03-1.13; OR, 1.10; 95% CI, 1.04-1.17; OR, 1.27; 95% CI, 1.16-1.39, respectively) were significantly associated with incident sarcoidosis (P < 0.0001). Conclusions: The incidence and prevalence of sarcoidosis are higher among veterans than in the general population. Alongside traditionally recognized risk factors such as Black race and female sex, we found that a history of tobacco use within the Veterans Affairs population and serving in the Army, Air Force, or multiple service branches were associated with increased sarcoidosis risk.

Sarcoidosis rates in BCG-vaccinated and unvaccinated young adults: A natural experiment using Danish registers

OBJECTIVES

Sarcoidosis may have an infectious trigger, including Mycobacterium spp. The Bacille Calmette-Guérin (BCG) vaccine provides partial protection against tuberculosis and induces trained immunity. We examined the incidence rate (IR) of sarcoidosis in Danish individuals born during high BCG vaccine uptake (born before 1976) compared with individuals born during low BCG vaccine uptake (born in or after 1976).

METHODS

We performed a quasi-randomized registry-based incidence study using data from the Danish Civil Registration System and the Danish National Patient Registry between 1995 and 2016. We included individuals aged 25-35 years old and born between 1970 and 1981. Using Poisson regression models, we calculated the incidence rate ratio (IRR) of sarcoidosis in individuals born during low BCG vaccine uptake versus high BCG vaccine uptake, adjusting for age and calendar year (separately for men and women).

RESULTS

The IR of sarcoidosis was increased for individuals born during low BCG vaccine uptake compared with individuals born during high BCG vaccine uptake, which was largely attributed to men. The IRR of sarcoidosis for men born during low BCG vaccine uptake versus high BCG vaccine uptake was 1.22 (95% confidence interval [CI] 1.02-1.45). In women, the IRR was 1.08 (95% CI 0.88-1.31).

CONCLUSION

In this quasi-experimental study that minimizes confounding, the time period with high BCG vaccine uptake was associated with a lower incidence rate of sarcoidosis in men, with a similar effect seen in women that did not reach significance. Our findings support a potential protective effect of BCG vaccination against the development of sarcoidosis. Future interventional studies for high-risk individuals could be considered.

Cardiac sarcoidosis: a comprehensive review of risk factors, pathogenesis, diagnosis, clinical manifestations, and treatment strategies

Cardiac Sarcoidosis (CS) is a deadly consequence of systemic sarcoidosis that inflames all three layers of the heart, especially the myocardium-clinical signs of CS range from asymptomatic disease to abrupt cardiac death. CS generally remains undiagnosed secondary to a lack of definitive diagnostic criteria, a high percentage of false negative results on endomyocardial biopsy, and ill-defining clinical manifestations of the disease. Consequently, there is a lack of evidence-based recommendations for CS, and the present diagnostic and therapeutic management depend on expert opinion. The aetiology, risk factors, clinical symptoms, diagnosis, and therapy of CS will be covered in this review. A particular emphasis will be placed on enhanced cardiovascular imaging and early identification of CS. We review the emerging evidence regarding the use of Electrocardiograms (ECGs), Magnetic Resonance Imaging (MRI), and Positron Emission Tomography (PET) imaging of the heart to identify and quantify the extent of myocardial inflammation, as well as to guide the use of immunotherapy and other treatment regimens, such as ablation therapy, device therapy, and heart transplantation, to improve patient outcomes.

Sarcoidosis and Autoimmune Inflammatory Syndrome Induced by Adjuvants

Currently, sarcoidosis remains one of the diseases with unknown etiology, which significantly complicates its diagnosis and treatment. Various causes of sarcoidosis have been studied for many years. Both organic and inorganic trigger factors, provoking the development of granulomatous inflammation are considered. However, the most promising and evidence-based hypothesis is the development of sarcoidosis as an autoimmune disease, provoked by various adjuvants in genetic predisposed individuals. This concept fits into the structure of the autoimmune/inflammatory syndrome, induced by adjuvants (ASIA) that was proposed in 2011 by Professor Shoenfeld Y. In this paper, the authors reveal the presence of major and minor ASIA criteria for sarcoidosis, propose a new concept of the course of sarcoidosis within the framework of ASIA, and point out the difficulties in creating a model of the disease and the selection of therapy. It is obvious that the data obtained not only bring us closer to understanding the nature of sarcoidosis, but also potentiate new studies confirming this hypothesis by obtaining a model of the disease.

Deconstructing Multiorgan Sarcoidosis

Sarcoidosis is a multisystem granulomatous disease of unknown cause [...]

Pulmonary sarcoid-like granulomatosis induced by aluminum dust: A case report and literature review

Case report

We present a case of a 48-year-old woman with 27 months of exposure to aluminum dust and silica owing to polishing processing. The patient was admitted to our hospital with intermittent cough and expectoration. Chest high-resolution computed tomography showed diffuse ill-defined centrilobular nodules and patchy ground-glass opacities in bilateral lungs. A video-assisted thoracoscopic surgery biopsy demonstrated multiple isolated and confluent granulomas in an otherwise normal parenchyma without malignancy or signs of infection. Elemental analysis was performed on the grinding wheel powder in the workplace using an X-ray fluorescence spectrometric analyzer, showing 72.7% of Al₂O₃ and 22.8% of SiO₂ as raw materials. She was diagnosed with aluminum-associated sarcoid-like granulomatous lung disease, rather than sarcoidosis, according to occupational exposure by a multidisciplinary panel.

Conclusion

Occupational aluminum dust exposure may induce pulmonary sarcoid-like granulomatosis recognized by a multidisciplinary diagnostic panel.

An expert overview of pulmonary fibrosis in sarcoidosis

INTRODUCTION

Advanced pulmonary sarcoidosis refers to phenotypes of pulmonary sarcoidosis that often lead to significant loss of lung function, respiratory failure, or death. Around 20% of patients with sarcoidosis may progress to this state which is mainly driven by advanced pulmonary fibrosis. Advanced fibrosis often presents with associated complications of sarcoidosis including infections, bronchiectasis, and pulmonary hypertension.

AREAS COVERED

This article will focus on the pathogenesis, natural history of disease, diagnosis, and potential treatment options of pulmonary fibrosis in sarcoidosis. In the expert opinion section, we will discuss the prognosis and management of patients with significant disease.

EXPERT OPINION

While some patients with pulmonary sarcoidosis remain stable or improve with anti-inflammatory therapies, others develop pulmonary fibrosis and further complications. Although advanced pulmonary fibrosis is the leading cause of death in sarcoidosis, there are no evidence-based guidelines for the management of fibrotic sarcoidosis. Current recommendations are based on expert consensus and often include multidisciplinary discussions with experts in sarcoidosis, pulmonary hypertension, and lung transplantation to facilitate care for such complex patients. Current works evaluating treatments include the use of antifibrotic therapies for treatment in advanced pulmonary sarcoidosis.

Factors associated with a diagnosis of sarcoidosis among US veterans of Iraq and Afghanistan

This study evaluated risk factors of sarcoidosis among Airborne Hazards and Open Burn Pit Registry (AHOBPR) participants using a retrospective age and sex-matched case-control design of AHOBPR participants deployed to Afghanistan or Southwest Asia with and without sarcoidosis diagnosed in the Veterans Health Administration (VHA). Logistic regression models tested for associations between sarcoidosis and self-reported cumulative deployment-related exposures. 661 Veterans (0.37%) were diagnosed with sarcoidosis in VHA. Logistic regression demonstrated lower odds of sarcoidosis in Hispanic participants (OR 0.08, CI 0.04-0.15) and those who served in the Navy (OR 0.40, CI 0.21-0.72). African American veterans (OR 2.27, CI 1.66-3.11) and former smokers (OR 1.87, CI 1.33-2.62) were at elevated risk. Of the exposure variables, convoy activities had the highest odds of being associated with sarcoidosis and was marginally statistically significant (OR 1.16, CI 1.00-1.35). Sarcoidosis was an uncommon diagnosis among AHOBPR participants and was associated with only one of eight assessed cumulative deployment-related exposures.

A Swollen Supraglottis

A woman in her late 20s presented with difficulty phonating and singing for the past 15 months and no improvement from prior treatment with steroids and antibiotics for chronic laryngitis. What is your diagnosis?

Sarcoidosis: Updates on therapeutic drug trials and novel treatment approaches

Sarcoidosis is a systemic granulomatous inflammatory disease of unknown etiology. It affects the lungs in over 90% of patients yet extra-pulmonary and multi-organ involvement is common. Spontaneous remission of disease occurs commonly, nonetheless, over 50% of patients will require treatment and up to 30% of patients will develop a chronic progressive non-remitting disease with marked pulmonary fibrosis leading to significant morbidity and death. Guidelines outlining an immunosuppressive treatment approach to sarcoidosis were recently published, however, the strength of evidence behind many of the guideline recommended drugs is weak. None of the drugs currently used for the treatment of sarcoidosis have been rigorously studied and prescription of these drugs is often based on off-label” indications informed by experience with other diseases. Indeed, only two medications [prednisone and repository corticotropin (RCI) injection] currently used in the treatment of sarcoidosis are approved by the United States Food and Drug Administration. This situation results in significant reimbursement challenges especially for the more advanced (and often more effective) drugs that are favored for severe and refractory forms of disease causing an over-reliance on corticosteroids known to be associated with significant dose and duration dependent toxicities. This past decade has seen a renewed interest in developing new drugs and exploring novel therapeutic pathways for the treatment of sarcoidosis. Several of these trials are active randomized controlled trials (RCTs) designed to recruit relatively large numbers of patients with a goal to determine the safety, efficacy, and tolerability of these new molecules and therapeutic approaches. While it is an exciting time, it is also necessary to exercise caution. Resources including research dollars and most importantly, patient populations available for trials are limited and thus necessitate that several of the challenges facing drug trials and drug development in sarcoidosis are addressed. This will ensure that currently available resources are judiciously utilized. Our paper reviews the ongoing and anticipated drug trials in sarcoidosis and addresses the challenges facing these and future trials. We also review several recently completed trials and draw lessons that should be applied in future.

Sarcoidosis: Progression to the chronic stage and pathogenic based treatment (narrative review)

Many factors confirm the autoimmune nature of sarcoidosis and help in determining the strategy of patient management and treatment initiation. However, the causes and the mechanisms of disease progression that result in fibrosis and insufficiency of the affected organ remain unclear. This narrative review aims to analyse the mechanisms and biomarkers of sarcoidosis progression, as well as the pathogenetic basis of sarcoidosis therapy. The following characteristics of progressive chronic sarcoidosis were revealed: the disease develops in patients with a genetic predisposition (SNP in genes GREM1, CARD15, TGF-β3, HLA-DQB1^*06:02, HLA-DRB1^*07/14/15), which contributes either the decreased ability of antigen elimination or autoimmune inflammation. Various prognostic biomarkers of disease progression (decreased levels of neopterin, elastase, sIL-2R, chitotriosidase, glycoprotein Krebs von den Lungen, Th17 cell count, reduced quantity of TNF-α in peripheral blood or bronchoalveolar lavage fluid) have been described and can potentially be used to determine the group of patients who will benefit from the use of corticosteroids/cytostatic drugs/biologics.

Sarcoidosis

Sarcoidosis is a systemic autoimmune disease that is associated with the development of non-caseating granulomas. The disease especially affects the lymph nodes, lungs, skin and eyes. It is an infrequent but not rare disease, especially in northern Europe, the United States and India. Sarcoidosis affects more women and is diagnosed between the ages of 30 and 50. Etiopathogenically, it is closely linked to environmental factors, especially occupational exposures. Clinically, it stands out for a wide variety of presentation phenotypes (casual diagnosis, involvement of a single organ or systemic presentation). The diagnosis of sarcoidosis is complex and requires the integration of clinical, analytical, radiological, and histolopathogical data carried out by multidisciplinary clinical units. The evolution of the disease is variable, as is the indication for systemic treatment, based on the use of corticosteroids as first-line option, the use of immunosuppressants as second-line therapy, and anti-TNF agents in severe and/or refractory cases.

Sarcoidosis with multiple organ involvement and uncommon symptoms: A case report

Sarcoidosis is a complicated inflammatory disease characterized by the formation of non‐caseating epithelioid granulomas in many organs. Herein, we reported a sarcoidosis case with multiple organ involvements and our diagnostic criteria and treatment plan.

The position of geochemical variables as causal co-factors of diseases of unknown aetiology

Abstract

The term diseases of unknown aetiology (DUA) or idiopathic diseases is used to describe diseases that are of uncertain or unknown cause or origin. Among plausible geoenvironmental co-factors in causation of DUA, this article focusses on the entry of trace elements, including metals and metalloids into humans, and their involvement in humoral and cellular immune responses, representing potentially toxic agents with implications as co-factors for certain DUA. Several trace elements/metals/metalloids (micronutrients) play vital roles as co-factors for essential enzymes and antioxidant molecules, thus, conferring protection against disease. However, inborn errors of trace element/metal/metalloid metabolisms can occur to produce toxicity, such as when there are basic defects in the element transport mechanism. Ultimately, it is the amount of trace element, metal or metalloid that is taken up, its mode of accumulation in human tissues, and related geomedical attributes such as the chemical form and bioavailability that decisively determine whether the exerted effects are toxic or beneficial. Several case descriptions of DUA that are common worldwide are given to illustrate our knowledge so far of how trace element/metal/metalloid interactions in the immune system may engender its dysregulation and be implicated as causal co-factors of DUA.

Article highlights

The importance of a proper understanding of geochemical perturbations in human metabolisms is emphasisedIt is proferred that such an understanding would aid greatly in the decipherment of diseases of unknown aetiology (DUA)The thesis presented may pave the way towards better diagnosis and therapy of DUA.

Sarcoid Uveitis: An Intriguing Challenger

The purpose of our work is to describe the actual knowledge concerning etiopathogenesis, clinical manifestations, diagnostic procedures, complications and therapy of ocular sarcoidosis (OS). The study is based on a recent literature review and on the experience of our tertiary referral center. Data were retrospectively analyzed from the electronic medical records of 235 patients (461 eyes) suffering from a biopsy-proven ocular sarcoidosis. Middle-aged females presenting bilateral ocular involvement are mainly affected; eye involvement at onset is present in one-third of subjects. Uveitis subtype presentation ranges widely among different studies: panuveitis and multiple chorioretinal granulomas, retinal segmental vasculitis, intermediate uveitis and vitreitis, anterior uveitis with granulomatous mutton-fat keratic precipitates, iris nodules, and synechiae are the main ocular features. The most important complications are cataract, glaucoma, cystoid macular edema (CME), and epiretinal membrane. Therapy is based on the disease localization and the severity of systemic or ocular involvement. Local, intravitreal, or systemic steroids are the mainstay of treatment; refractory or partially responsive disease has to be treated with conventional and biologic immunosuppressants. In conclusion, we summarize the current knowledge and assessment of ophthalmological inflammatory manifestations (mainly uveitis) of OS, which permit an early diagnostic assay and a prompt treatment.

Occupational exposures and sarcoidosis: current understanding and knowledge gaps

PURPOSE OF REVIEW

Sarcoidosis is an idiopathic granulomatous disease that primarily affects the lungs. Several lines of evidence suggest that occupational exposures are associated with disease risk. This review critically evaluates studies using the Bradford Hill criteria for causation to determine if a causal relationship can be established between occupational exposure and sarcoidosis.

RECENT FINDINGS

Large epidemiological studies have proposed multiple occupational exposures associated with sarcoidosis but lack consistency of results. Many convincing studies demonstrate an association between World Trade Center (WTC) dust and sarcoidosis, which illustrates a causal relationship based on the fulfillment of the Bradford Hill criteria. Studies describing an association between silica/metals and sarcoidosis are intriguing but fulfill a limited number of the Bradford Hill criteria and warrant further investigation before a causal relationship can be determined. Finally, we also discuss preliminary studies associating sarcoidosis phenotypes with specific occupational exposures.

SUMMARY

Using the Bradford Hill criteria for causation, we demonstrate that WTC dust has a causative relationship with sarcoidosis, which reinforces the theory that sarcoidosis is an exposure-related disease. More research is needed to determine other specific occupational exposures causing disease.

Sarcoid-like Granulomatous Lung Disease with Subacute Progression in Silicosis

A 67-year-old man was admitted to our hospital with cough and fatigue. He had had long-term exposure to silica due to cement processing. Chest computed tomography showed bilateral centrilobular nodules, and hilar and mediastinal lymphadenopathy with calcification, suggesting chronic silicosis. Within a few months, these nodules enlarged, and bilateral patchy consolidations appeared. A lung biopsy revealed sarcoid-like granulomas with birefringent particles under polarized light without malignancy or infection. He was diagnosed with silicosis-associated sarcoid-like granulomatous lung disease, rather than sarcoidosis, according to the clinicopathological findings. His pulmonary manifestations improved after the discontinuation of silica exposure and combination therapy of corticosteroid and azathioprine.

Myeloid ABCG1 Deficiency Enhances Apoptosis and Initiates Efferocytosis in Bronchoalveolar Lavage Cells of Murine Multi-Walled Carbon Nanotube-Induced Granuloma Model

The use of carbon nanotubes has increased in the past few decades. Carbon nanotubes are implicated in the pathogenesis of pulmonary sarcoidosis, a chronic granulomatous inflammatory condition. We developed a murine model of chronic granulomatous inflammation using multiwall carbon nanotubes (MWCNT) to investigate mechanisms of granuloma formation. Using this model, we demonstrated that myeloid deficiency of ATP-binding cassette (ABC) cholesterol transporter (ABCG1) promotes granuloma formation and fibrosis with MWCNT instillation; however, the mechanism remains unclear. Our previous studies showed that MWCNT induced apoptosis in bronchoalveolar lavage (BAL) cells of wild-type (C57BL/6) mice. Given that continual apoptosis causes persistent severe lung inflammation, we hypothesized that ABCG1 deficiency would increase MWCNT-induced apoptosis thereby promoting granulomatous inflammation and fibrosis. To test our hypothesis, we utilized myeloid-specific ABCG1 knockout (ABCG1 KO) mice. Our results demonstrate that MWCNT instillation enhances pulmonary fibrosis in ABCG1 KO mice compared to wild-type controls. Enhanced fibrosis is indicated by increased trichrome staining and transforming growth factor-beta (TGF-β) expression in lungs, together with an increased expression of TGF-β related signaling molecules, interleukin-13 (IL-13) and Smad-3. MWCNT induced more apoptosis in BAL cells of ABCG1 KO mice. Initiation of apoptosis is most likely mediated by the extrinsic pathway since caspase 8 activity and Fas expression are significantly higher in MWCNT instilled ABCG1 KO mice compared to the wild type. In addition, TUNEL staining shows that ABCG1 KO mice instilled with MWCNT have a higher percentage of TUNEL positive BAL cells and more efferocytosis than the WT control. Furthermore, BAL cells of ABCG1 KO mice instilled with MWCNT exhibit an increase in efferocytosis markers, milk fat globule-EGF factor 8 (MFG-E8) and integrin β3. Therefore, our observations suggest that ABCG1 deficiency promotes pulmonary fibrosis by MWCNT, and this effect may be due to an increase in apoptosis and efferocytosis in BAL cells.

The M2a Macrophage Phenotype Accompanies Pulmonary Granuloma Resolution in Mmp12 Knock-Out Mice Instilled with Multiwall Carbon Nanotubes

Sarcoidosis is a chronic disease with unknown etiology and pathophysiology, characterized by granuloma formation. Matrix Metalloproteinase-12 (MMP12) is an elastase implicated in active granulomatous sarcoidosis. Previously, we reported that oropharyngeal instillation of multiwall carbon nanotubes (MWCNT) into C57Bl/6 mice induced sarcoid-like granulomas and upregulation of MMP12. When Mmp12 knock-out (KO) mice were instilled with MWCNT, granuloma formation occurred 10 days post-instillation but subsequently resolved at 60 days. Thus, we concluded that MMP12 was essential to granuloma persistence. The aim of the current study was to identify potential mechanisms of granuloma resolution in Mmp12KO mice. Strikingly, an M2 macrophage phenotype was present in Mmp12KO but not in C57Bl/6 mice. Between 10 and 60 days, macrophage populations in MWCNT-instilled Mmp12KO mice demonstrated an M2c to M2a phenotypic shift, with elevations in levels of IL-13, an M2 subtype-regulating factor. Furthermore, the M2 inducer, Apolipoprotein E (ApoE), and Matrix Metalloproteinase-14 (MMP14), a promoter of collagen degradation, were upregulated in 60-day MWCNT-instilled Mmp12KO mice. In conclusion, alveolar macrophages express two M2 phenotypes in Mmp12KO mice: M2c at 10 days when granulomas form, and M2a at 60 days when granulomas are resolving. Findings suggest that granuloma resolution in 60-day Mmp12KO mice requires an M2a macrophage phenotype.

Cardiac Sarcoidosis: A Clinical Overview

Cardiac sarcoidosis (CS) with clinical manifestation occurs in about 5-8% of patients with sarcoidosis. CS may be clinically suspected by the presence of ventricular arrhythmia, conduction abnormalities, and heart failure (HF). However, 20%-25% of patients may present with silent CS, having asymptomatic cardiac involvement. The diagnosis of CS is based on findings from nuclear studies, cardiac magnetic resonance, and extra-cardiac tissue biopsy. Due to the inflammatory nature of the disease, immunosuppressive medications are a cornerstone of therapy. The treatment also includes recommended HF medical therapies. Since CS patients are at risk of sudden cardiac death resulting from progression of cardiac dysfunction or the presence of scar originating from fatal arrhythmias, implantable cardioverter-defibrillators should be considered, with special indication beyond accepted recommendations in HF. In CS, the extent of left ventricular dysfunction is the most important mortality predictor. Heart transplant or mechanical circulatory support may represent life saving strategies in selective CS patients.

Granulomatous Sarcoidosis Mimics

Many granulomatous diseases can mimic sarcoidosis histologically and in terms of their clinical features. These mimics include infectious granulomatous diseases, granulomatous reactions to occupational and environmental exposures, granulomatous drug reactions, vasculitides and idiopathic granulomatous conditions. It is important to distinguish sarcoidosis from these mimics, as a misdiagnosis of these diseases may have serious consequences. This manuscript reviews numerous sarcoidosis mimics and describes features of these diseases that may allow them to be differentiated from sarcoidosis. Distinguishing features between sarcoidosis and its mimics requires a careful review of the medical history, symptoms, demographics, radiographic findings, histologic features, and additional laboratory data. Understanding the clinical characteristics of sarcoidosis and its mimics should lead to more accurate diagnoses and treatment of granulomatous disorders that should improve the care of these patients. As the diagnostic criteria of sarcoidosis are not standardized, it is possible that some of these sarcoidosis mimics may represent varied clinical presentations of sarcoidosis itself.

A Primer on the Clinical Aspects of Sarcoidosis for the Basic and Translational Scientist

The immunopathogenesis of sarcoidosis remains unclear. This failure in understanding has been clinically impactful, as it has impeded the accurate diagnosis, treatment, and prevention of this disease. Unraveling the mechanisms of sarcoidosis will require input from basic and translational scientists. In order to reach this goal, scientists must have a firm grasp of the clinical aspects of the disease, including its diagnostic criteria, the immunologic defects, clinical presentations, response to therapy, risk factors, and clinical course. This manuscript will provide an overview of the clinical aspects of sarcoidosis that are particularly relevant for the basic and translational scientist. The variable phenotypic expression of the disease will be described, which may be integral in identifying immunologic disease mechanisms that may be relevant to subgroups of sarcoidosis patients. Data concerning treatment and risk factors may yield important insights concerning germane immunologic pathways involved in the development of disease. It is hoped that this manuscript will stimulate communication between scientists and clinicians that will eventually lead to improved care of sarcoidosis patients.

Inflammatory Pathways in Sarcoidosis

Concepts regarding etiology and pathophysiology of sarcoidosis have changed remarkably within the past 5 years. Sarcoidosis is now viewed as a complex multi-causation disease related to a diverse collection of external environmental or infectious signals. It is generally accepted that the cause of sarcoidosis is unknown. Moreover, concepts of the inflammatory pathway have been modified by the realization that intrinsic genetic factors and innate immunity may modify adaptive immune responses to external triggers. With those potential regulatory pathways in mind, we will attempt to discuss the current understanding of the inflammatory response in sarcoidosis with emphasis on development of pulmonary granulomatous pathology. In that context, we will emphasize that both macrophages and T lymphocytes play key roles, with sometimes overlapping cytokine production (i.e., TNFα and IFN-γ) but also with unique mediators that influence the pathologic picture. Numerous studies have shown that in a sizable number of sarcoidosis patients, granulomas spontaneously resolve, usually within 3 years. Other sarcoidosis patients, however, may develop a chronic granulomatous disease which may subsequently lead to fibrosis. This chapter will outline our current understanding of inflammatory pathways in sarcoidosis which initiate and mediate granulomatous changes or onset of pulmonary fibrosis.

Studies in a Murine Granuloma Model of Instilled Carbon Nanotubes: Relevance to Sarcoidosis

Poorly soluble environmental antigens, including carbon pollutants, are thought to play a role in the incidence of human sarcoidosis, a chronic inflammatory granulomatous disease of unknown causation. Currently, engineered carbon products such as multiwall carbon nanotubes (MWCNT) are manufactured commercially and have been shown to elicit acute and chronic inflammatory responses in experimental animals, including the production of granulomas or fibrosis. Several years ago, we hypothesized that constructing an experimental model of chronic granulomatosis resembling that associated with sarcoidosis might be achieved by oropharyngeal instillation of MWCNT into mice. This review summarizes the results of our efforts to define mechanisms of granuloma formation and identify potential therapeutic targets for sarcoidosis. Evidence is presented linking findings from the murine MWCNT granuloma model to sarcoidosis pathophysiology. As our goal was to determine what pulmonary inflammatory pathways might be involved, we utilized mice of knock-out (KO) backgrounds which corresponded to deficiencies noted in sarcoidosis patients. A primary example of this approach was to study mice with a myeloid-specific knock-out of the lipid-regulated transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ) which is strikingly depressed in sarcoidosis. Among the major findings associated with PPARγ KO mice compared to wild-type were: (1) exacerbation of granulomatous and fibrotic histopathology in response to MWCNT; (2) elevation of inflammatory mediators; and (3) pulmonary retention of a potentially antigenic ESAT-6 peptide co-instilled with MWCNT. In line with these data, we also observed that activation of PPARγ in wild-type mice by the PPARγ-specific ligand, rosiglitazone, significantly reduced both pulmonary granuloma and inflammatory mediator production. Similarly, recognition of a deficiency of ATP-binding cassette (ABC) lipid transporter ABCG1 in sarcoidosis led us to study MWCNT instillation in myeloid-specific ABCG1 KO mice. As anticipated, ABCG1 deficiency was associated with larger granulomas and increased levels of inflammatory mediators. Finally, a transcriptional survey of alveolar macrophages from MWCNT-instilled wild-type mice and human sarcoidosis patients revealed several common themes. One of the most prominent mediators identified in both human and mouse transcriptomic analyses was MMP12. Studies with MMP12 KO mice revealed similar acute reactions to those in wild-type but at chronic time points where wild-type maintained granulomatous disease, resolution occurred with MMP12 KO mice suggesting MMP12 is necessary for granuloma progression. In conclusion, these studies suggest that the MWCNT granuloma model has relevance to human sarcoidosis study, particularly with respect to immune-specific pathways.

Artificial stone silicosis

PURPOSE OF REVIEW

This review details recent findings related to the health effects of occupational exposure to artificial stone dust and the rapid increase in cases of artificial stone associated silicosis around the world.

RECENT FINDINGS

High crystalline silica content artificial stone is now commonly used for the production of kitchen benchtops. Reports of artificial stone silicosis from many countries have noted that workers were typically employed at small workplaces and were often diagnosed in their 30s or 40s. Poor exposure control measures were common, including the practice of 'dry processing'. Dust generated from artificial stone has been noted to have properties that influence toxicity, including high silica content, generation of nanosized particles and presence of metals and resins. Artificial stone silicosis differs from silicosis associated with other occupational settings including shorter latency and rapid disease progression. High-resolution computed tomography (CT) chest imaging of artificial stone silicosis has often noted the presence of ground glass opacities, which may not be detected in chest x-ray screening. Increased prevalence of autoimmune disease, such as scleroderma, has also been reported in this industry.

SUMMARY

Further evaluation of the safety of work with artificial stone is required, including the effectiveness of dust control measures. Current reports of artificial stone silicosis indicate the potential for widespread undiagnosed respiratory disease in this industry. Provision of more sensitive health screening methods for all at-risk workers and the development of new treatment options particularly for this form of silicosis is urgently required.

Sarcoidosis: a prospective observational cohort from Northern Alberta

INTRODUCTION

Sarcoidosis is a multi-system disease reported to occur with a higher incidence in Alberta than many other health jurisdictions within and outside of Canada. The reasons for this higher incidence are currently not known. Exposure to beryllium can result in a clinically and radiologically identical disease to sarcoidosis. The purpose of our study was to identify patterns with potential occupational or environmental exposures to beryllium amongst individuals with sarcoidosis in Alberta through a tertiary referral center.

METHODS

A prospective observational study was carried out at the University of Alberta Hospital. Patients with confirmed sarcoidosis (stages 0-4) were recruited from subspecialty clinics (Respirology, Cardiology, Neurology and Occupational Health). A predetermined list of industries thought to involve potentially relevant exposures for the development of sarcoidosis was used to capture current and previous exposure history. Results were entered into a database and where possible verified by comparing with existing electronic medical records (including histories, physical examination, diagnostic imaging and physiology).

RESULTS

A total of 45 patients were recruited, 25 men and 20 women. Of these, 84% of participants reported working in or being exposed to an industry/environment suspected of contributing to development of sarcoidosis over their lifetime. The most frequently reported exposures were within farming and agriculture (27%), oil and gas (20%), metalworking and handling animals (18%).

CONCLUSIONS

Amongst this cohort, a high proportion reported working with a potentially relevant exposure. Individuals being assessed for sarcoidosis should have their most responsible physician elicit a detailed work and environmental history. (Sarcoidosis Vasc Diffuse Lung Dis 2020; 37 (4): e2020014).

CT Findings in Pulmonary and Abdominal Sarcoidosis. Implications for Diagnosis and Classification

Sarcoidosis is a granulomatous disorder of unknown etiology characterized by noncaseating granulomas virtually in every organ and tissue. This finding represents the most important diagnostic clue to reach a correct definition of sarcoidosis, although the biopsy is invasive and has several risk procedures. Several efforts are made to suspect the diagnosis of sarcoidosis by combining noninvasive elements, in particular from imaging, though these findings are often nonspecific and reflect the wide multifactorial pathogenesis. Every effort should be made to obtain a detailed radiological picture that, if associated with a suggestive clinical picture, could avoid the need of biopsy in some specific cases. In this narrative review, we aim to describe main computed tomography (CT) features of pulmonary and abdominal sarcoidosis, by reporting strengths and limits of this technique, in particular for the identification of extrapulmonary, isolated disease.

Matrix Metalloproteinase-12 Is Required for Granuloma Progression

Background

Sarcoidosis is a chronic inflammatory disease of unknown cause characterized by granuloma formation. Mechanisms for chronic persistence of granulomas are unknown. Matrix Metalloproteinase-12 (MMP12) degrades extracellular matrix elastin and enables infiltration of immune cells responsible for inflammation and granuloma formation. Previous studies report increased MMP12 in sarcoidosis patients and association between MMP12 expression and disease severity. We also observed elevated MMP12 in our multiwall carbon nanotube (MWCNT) murine model of granulomatous inflammation. Here we hypothesized that MMP12 is important to acute and late phases of granuloma pathogenesis. To test this hypothesis, we analyzed granulomatous and inflammatory responses of Mmp12 knock-out (KO) mice at 10 (acute) and 60 days (late) after MWCNT instillation.

Methods

C57BL/6 (wildtype) and Mmp12 KO mice underwent oropharyngeal instillation of MWCNT. Lungs were harvested at 3, 10, 20, and 60 days post instillation for evaluation of MMP12 expression and granulomatous changes. Bronchoalveolar lavage (BAL) cells were analyzed 60 days after MWCNT instillation for expression of mediators thought to play a role in sarcoid granulomatosis: peroxisome proliferator-activated receptor-gamma (PPARγ), interferon-gamma (IFN-γ), and CCL2 (MCP-1).

Results

Pulmonary granuloma appearance at 10 days after MWCNT instillation showed no differences between wildtype and Mmp12 KO mice. In contrast, by 60 days after MWCNT instillation, Mmp12 KO mice revealed markedly attenuated granuloma formation together with elevated PPARγ and reduced IFNγ expression in BAL cells compared to wildtype. Unexpectedly, Mmp12 KO mice further demonstrated increased alveolar macrophages with increased CCL2 at 60 days.

Conclusions

The striking reduction of granuloma formation at day 60 in Mmp12 KO mice suggests that MMP12 is required to maintain chronic granuloma pathophysiology. The increased PPARγ and decreased IFNγ findings suggest that these mediators also may be involved since previous studies have shown that PPARγ suppresses IFNγ and PPARγ deficiency amplifies granuloma formation. Interestingly, a role of MMP12 in granuloma resolution is also suggested by increases in both macrophage influx and CCL2. Overall, our results strongly implicate MMP12 as a key factor in granuloma persistence and as a possible therapeutic target in chronic pulmonary sarcoidosis.