Immunogenetics of Disease-Causing Inflammation in Sarcoidosis

The immunopathogenesis of sarcoidosis

Sarcoidosis is a granulomatous multiorgan disease, thought to result from exposure to yet unidentified antigens in genetically susceptible individuals. The exaggerated inflammatory response that leads to granuloma formation is highly complex and involves the innate and adaptive immune system. Consecutive immunological studies using advanced technology have increased our understanding of aberrantly activated immune cells, mediators and pathways that influence the formation, maintenance and resolution of granulomas. Over the years, it has become increasingly clear that disease immunopathogenesis can only be understood if the clinical heterogeneity of sarcoidosis is taken into consideration, along with the distribution of immune cells in peripheral blood and involved organs. Most studies offer an immunological snapshot during disease course, while the cellular composition of both the circulation and tissue microenvironment may change over time. Despite these challenges, novel insights on the role of the immune system are continuously published, thus bringing the field forward. This review highlights current knowledge on the innate and adaptive immune responses involved in sarcoidosis pathogenesis, as well as the pathways involved in non-resolving disease and fibrosis development. Additionally, we describe proposed immunological mechanisms responsible for drug-induced sarcoid like reactions. Although many aspects of disease immunopathogenesis remain to be unraveled, the identification of crucial immune reactions in sarcoidosis may help identify new treatment targets. We therefore also discuss potential therapies and future strategies based on the latest immunological findings.

The role of the host-microbiome and metabolomics in sarcoidosis

Sarcoidosis is a complex inflammatory fibrotic disease that affects multiple organ systems. It is characterized by the infiltration of lymphocytes and mononuclear phagocytes, which form non-caseating granulomas in affected organs. The lungs and intrathoracic lymph nodes are the most commonly affected organs. The underlying cause of sarcoidosis is unknown, but it is believed to occur in genetically predisposed individuals who are exposed to pathogenic organisms, environmental contaminants, or self and non-self-antigens. Recent research has suggested that the microbiome may play a role in the development of respiratory conditions, including sarcoidosis. Additionally, metabolomic studies have identified potential biomarkers for monitoring sarcoidosis progression. This review will focus on recent microbiome and metabolomic findings in sarcoidosis, with the goal of shedding light on the pathogenesis and possible diagnostic and therapeutic approaches.

T-cell signature cytokines distinguish pulmonary sarcoidosis from pulmonary tuberculosis

Sarcoidosis is a systemic inflammatory disorder characterized by tissue infiltration due to mononuclear phagocytes and lymphocytes and associated noncaseating granuloma formation. Pulmonary sarcoidosis (PS) shares a number of clinical, radiological, and histopathological characteristics with that of pulmonary tuberculosis (PTB). Due to this, clinicians face issues in differentiating between PS and PTB in a substantial number of cases. There is a lack of any specific biomarker that can diagnose PS distinctively from PTB. We compared T-cell-based signature cytokines in patients with PS and PTB. In this study, we proposed a serum biomarker panel consisting of cytokines from cells: T helper (Th) 1 [interferon-gamma (IFN-γ); tumor necrosis factor-alpha (TNF-α)], Th9 [interleukin (IL)-9], Th17 [IL-17], and T regulatory (Treg) [IL-10; transforming growth factor-beta (TGF-β)]. We performed the principal component analysis that demonstrated that our serum cytokine panel has a significant predictive ability to differentiate PS from PTB. Our results could aid clinicians to improve the diagnostic workflow for patients with PS in TB endemic settings where the diagnosis between PS and PTB is often ambiguous.

From Karl Wurm and Guy Scadding's staging to 18F-FDG PET/CT scan phenotyping and far beyond: perspective in the evading history of phenotyping in sarcoidosis

Sarcoidosis is an inflammatory granulomatous disease of unknown etiology involving any organ or tissue along with any combination of active sites, even the most silent ones clinically. The unpredictable nature of the sites involved in sarcoidosis dictates the highly variable natural history of the disease and the necessity to cluster cases at diagnosis based on clinical and/or imaging common characteristics in an attempt to classify patients based on their more homogeneous phenotypes, possibly with similar clinical behavior, prognosis, outcome, and therefore with therapeutic requirements. In the course of the disease's history, this attempt relates to the availability of a means of detection of the sites involved, from the Karl Wurm and Guy Scadding's chest x-ray staging through the ACCESS, the WASOG Sarcoidosis Organ Assessment Instruments, and the GenPhenReSa study to the 18F-FDG PET/CT scan phenotyping and far beyond to new technologies and/or the current "omics." The hybrid molecular imaging of the 18F-FDG PET/CT scan, by unveiling the glucose metabolism of inflammatory cells, can identify high sensitivity inflammatory active granulomas, the hallmark of sarcoidosis-even in clinically and physiologically silent sites-and, as recently shown, is successful in identifying an unexpected ordered stratification into four phenotypes: (I) hilar-mediastinal nodal, (II) lungs and hilar-mediastinal nodal, (III) an extended nodal supraclavicular, thoracic, abdominal, inguinal, and (IV) all the above in addition to systemic organs and tissues, which is therefore the ideal phenotyping instrument. During the "omics era," studies could provide significant, distinct, and exclusive insights into sarcoidosis phenotypes linking clinical, laboratory, imaging, and histologic characteristics with molecular signatures. In this context, the personalization of treatment for sarcoidosis patients might have reached its goal.

Sarcoidosis, Mycobacterium paratuberculosis and Noncaseating Granulomas: Who Moved My Cheese

Clinical and histological similarities between sarcoidosis and tuberculosis have driven repeated investigations looking for a mycobacterial cause of sarcoidosis. Over 50 years ago, "anonymous mycobacteria" were suggested to have a role in the etiology of sarcoidosis. Both tuberculosis and sarcoidosis have a predilection for lung involvement, though each can be found in any area of the body. A key histopathologic feature of both sarcoidosis and tuberculosis is the granuloma-while the tuberculous caseating granuloma has an area of caseous necrosis with a cheesy consistency; the non-caseating granuloma of sarcoidosis does not have this feature. This article reviews and reiterates the complicity of the infectious agent, Mycobacterium avium subsp. paratuberculosis (MAP) as a cause of sarcoidosis. MAP is involved in a parallel story as the putative cause of Crohn's disease, another disease featuring noncaseating granulomas. MAP is a zoonotic agent infecting ruminant animals and is found in dairy products and in environmental contamination of water and air. Despite increasing evidence tying MAP to several human diseases, there is a continued resistance to embracing its pleiotropic roles. "Who Moved My Cheese" is a simple yet powerful book that explores the ways in which individuals react to change. Extending the metaphor, the "non-cheesy" granuloma of sarcoidosis actually contains the difficult-to-detect "cheese", MAP; MAP did not move, it was there all along.

Sarcoidosis: Epidemiology and clinical insights

Sarcoidosis is characterized by noncaseating granulomas which form in almost any part of the body, primarily in the lungs and/or thoracic lymph nodes. Environmental exposures in genetically susceptible individuals are believed to cause sarcoidosis. There is variation in incidence and prevalence by region and race. Males and females are almost equally affected, although disease peaks at a later age in females than in males. The heterogeneity of presentation and disease course can make diagnosis and treatment challenging. Diagnosis is suggestive in a patient if one or more of the following is present: radiologic signs of sarcoidosis, evidence of systemic involvement, histologically confirmed noncaseating granulomas, sarcoidosis signs in bronchoalveolar lavage fluid (BALF), and low probability or exclusion of other causes of granulomatous inflammation. No sensitive or specific biomarkers for diagnosis and prognosis exist, but there are several that can be used to support clinical decisions, such as serum angiotensin-converting enzyme levels, human leukocyte antigen types, and CD4 Vα2.3+ T cells in BALF. Corticosteroids remain the mainstay of treatment for symptomatic patients with severely affected or declining organ function. Sarcoidosis is associated with a range of adverse long-term outcomes and complications, and with great variation in prognosis between populations. New data and technologies have moved sarcoidosis research forward, increasing our understanding of the disease. However, there is still much left to be discovered. The pervading challenge is how to account for patient variability. Future studies should focus on how to optimize current tools and develop new approaches so that treatment and follow-up can be targeted to individuals with more precision.

Sarcoidosis

Sarcoidosis is a disease of unknown cause characterized by granulomatous inflammation. Although the lung is almost universally involved, any organ can be affected. Complex pathogenesis and protean clinical manifestations are additional features of the disease. The diagnosis is one of exclusion, although the presence of noncaseating granulomas at disease sites is a prerequisite in most cases. The management of sarcoidosis requires a multidisciplinary approach, particularly when the heart, the brain, or the eyes are involved. The paucity of effective therapies and the lack of reliable predictors of disease behavior greatly contribute to making sarcoidosis a challenging disease to manage.

Functional link between sarcoidosis-associated gene variants and quantitative levels of bronchoalveolar lavage fluid cell types

Background

Sarcoidosis is an inflammatory disease that affects multiple organs. Cell analysis from bronchoalveolar lavage fluid (BALF) is a valuable tool in the diagnostic workup and differential diagnosis of sarcoidosis. Besides the expansion of lymphocyte expression-specific receptor segments (Vα2.3 and Vβ22) in some patients with certain HLA types, the relation between sarcoidosis susceptibility and BAL cell populations' quantitative levels is not well-understood.

Methods

Quantitative levels defined by cell concentrations of BAL cells and CD4⁺/CD8⁺ ratio were evaluated together with genetic variants associated with sarcoidosis in 692 patients with extensive clinical data. Genetic variants associated with clinical phenotypes, Löfgren's syndrome (LS) and non-Löfgren's syndrome (non-LS), were examined separately. An association test via linear regression using an additive model adjusted for sex, age, and correlated cell type was applied. To infer the biological function of genetic associations, enrichment analysis of expression quantitative trait (eQTLs) across publicly available eQTL databases was conducted.

Results

Multiple genetic variants associated with sarcoidosis were significantly associated with quantitative levels of BAL cells. Specifically, LS genetic variants, mainly from the HLA locus, were associated with quantitative levels of BAL macrophages, lymphocytes, CD3⁺ cells, CD4⁺ cells, CD8⁺ cells, CD4⁺/CD8⁺ ratio, neutrophils, basophils, and eosinophils. Non-LS genetic variants were associated with quantitative levels of BAL macrophages, CD8⁺ cells, basophils, and eosinophils. eQTL enrichment revealed an influence of sarcoidosis-associated SNPs and regulation of gene expression in the lung, blood, and immune cells.

Conclusion

Genetic variants associated with sarcoidosis are likely to modulate quantitative levels of BAL cell types and may regulate gene expression in immune cell populations. Thus, the role of sarcoidosis-associated gene-variants may be to influence cellular phenotypes underlying the disease immunopathology.

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.

[Sarcoidosis as prime example of a granulomatous disease]

Sarcoidosis is the most frequent immunologically related granulomatous disease and can serve as a model for understanding diseases within this category. The evidence on the diagnostics and treatment is so far limited. It is therefore all the more important that two new and significant guidelines on diagnosis and treatment of sarcoidosis were published during the last 2 years. Additionally, there were more new publications, which were considered for this review article. In this context, this review article provides a current update and overview of sarcoidosis. Pathophysiologically, there is an increasing understanding of the complex processes and interactions involved in the inflammatory processes and granuloma formation. The probability of a diagnosis of sarcoidosis is determined by compatible histology, the exclusion of differential diagnoses and if possible evidence of a multiorgan manifestation. The clinical course is variable and ranges from an asymptomatic manifestation to severe life-threatening organ failure. The most frequently affected organ are the lungs. Pulmonary fibrosis is the most severe form and is also decisive for mortality. An increasing focus is on the extrapulmonary organ manifestations, in particular, cardiac, hepatosplenic, gastrointestinal, renal, ocular and neurological involvement. Treatment, which consists primarily of immunosuppression, should be initiated in cases of organ-threatening or quality of life-impairing activity of the disease. Additional organ-specific management must also be evaluated. In cases of organ failure transplantation should be considered. Due to the limited evidence especially for the treatment of multiorgan sarcoidosis, when possible, patients with this disease should be included in clinical trials.

Exome Sequencing Reveals Genetic Variability and Identifies Chronic Prognostic Loci in Chinese Sarcoidosis Patients

Background

Sarcoidosis is an inflammatory disease characterized by non-caseating granuloma formation in various organs, with several recognized genetic and environmental risk factors. Despite substantial progress, the genetic determinants associated with its prognosis remain largely unknown.

Objectives

This study aimed to identify the genetic changes involved in sarcoidosis and evaluate their clinical relevance.

Methods

We performed whole-exome sequencing (WES) in 116 sporadic sarcoidosis patients (acute sarcoidosis patients, n=58; chronic sarcoidosis patients, n=58). In addition, 208 healthy controls were selected from 1000 G East Asian population data. To identify genes enriched in sarcoidosis, Fisher exact tests were performed. The identified genes were included for further pathway analysis using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). Additionally, we used the STRING database to construct a protein network of rare variants and Cytoscape to identify hub genes of signaling pathways.

Results

WES and Fisher’s exact test identified 1,311 variants in 439 protein-coding genes. A total of 135 single nucleotide polymorphisms (SNPs) on 30 protein-coding genes involved in the immunological process based on the GO and KEGG enrichment analysis. Pathway enrichment analysis showed osteoclast differentiation and cytokine–cytokine receptor interactions. Three missense mutations (rs76740888, rs149664918, and rs78251590) in two genes (PRSS3 and CNN2) of immune-related genes showed significantly different mutation frequencies between the disease group and healthy controls. The correlation of genetic abnormalities with clinical outcomes using multivariate analysis of the clinical features and mutation loci showed that the missense variant (rs76740888, Chr9:33796673 G>A) of PRSS3 [p=0.04, odds ratio (OR) = 2.49] was significantly associated with chronic disease prognosis. Additionally, the top two hub genes were CCL4 and CXCR4 based on protein–protein interaction (PPI) network analysis.

Conclusion

Our study provides new insights into the molecular pathogenesis of sarcoidosis and identifies novel genetic alterations in this disease, especially PRSS3, which may be promising targets for future therapeutic strategies for chronic sarcoidosis.

Sarcoid-like Granulomatosis Associated with Immune Checkpoint Inhibitors in Melanoma

We aimed to review the clinical and biological presentation of granulomatosis associated with immune-checkpoint inhibitors (ICI) in patients with melanoma and to explore its association with classical sarcoidosis as well as with cancer response to ICI. To this end, a retrospective study on 18 melanoma patients with histologically proven ICI-induced granulomatosis over a 12-year period in a single center, as well as on 67 similar cases reported in the literature, was conducted. Results indicate ICI-induced granulomatosis is an early side effect (median time to onset: 2 months). Its clinical presentation, with predominant (90%) thoracic involvement, histopathological appearance and supposed underlying biology (involving the mTOR pathway in immune cells, Th17 polarization and TReg dysfunction) are indistinguishable from those of sarcoidosis. Moreover, it appears to be associated with ICI benefit (>65% objective response rate). Evolution is generally favorable, and symptomatic steroid treatment and/or ICI discontinuation are rarely necessary. ICI-associated granulomatosis is critical to explore for several reasons. Practically, it is essential to differentiate it from cancer progression. Secondly, this “experimental” sarcoidosis brings new elements that may help to address sarcoidosis origin and pathophysiology. Its association with ICI efficacy must be confirmed on a larger scale but could have significant impacts on patient management and biomarker definition.

Sarcoidosis in Northern Ontario hard-rock miners: A case series

Sarcoidosis is a rare multisystem granulomatous disease traditionally considered to be of unknown etiology. The notion that sarcoidosis has no known cause is called into question with the increasing number of case reports and epidemiologic studies showing associations between occupational exposures and disease published in the past 10-20 years. Occupational exposures for which associations are strongest and most consistent are silica and other inorganic dusts, World Trade Center (WTC) dust, and metals. Occupations identified as at-risk for sarcoidosis include construction workers; iron-foundry and diatomaceous earth workers; WTC emergency responders; and metal workers. We report here 12 cases of sarcoidosis in a cohort of hard-rock miners in Northern Ontario, Canada. To our knowledge sarcoidosis has not been reported previously in hard-rock miners. The cases are all male and Caucasian, with average age 74 years. At the time of diagnosis, two were never smokers; six, former smokers; and four, current smokers. Five have extrapulmonary sarcoidosis: two cardiac and three endocrine (hypercalciuria). Using occupational histories and air sampling data from the gold, uranium, and base-metal mines in which they worked, we examined exposure of each case to respirable crystalline silica (RCS). The annual mean RCS exposure for the 12 cases was 0.14 mg/m³ (range: 0.06-1.3 mg/m³ ); and the mean cumulative RCS exposure was 1.93 mg/m³  years (range: 0.64-4.03 mg/m³  years). We also considered their exposure to McIntyre Powder, an aluminum powder used for silicosis prophylaxis.

Pulmonary Sarcoidosis: Diagnosis and Differential Diagnosis

Sarcoidosis is a multisystem disorder of unknown origin and poorly understood pathogenesis that predominantly affects lungs and intrathoracic lymph nodes and is characterized by the presence of noncaseating granulomatous inflammation in involved organs. The disease is highly heterogeneous and can mimic a plethora of other disorders, making diagnosis a challenge even for experienced physicians. The evolution and severity of sarcoidosis are highly variable: many patients are asymptomatic and their disease course is generally benign with spontaneous resolution. However, up to one-third of patients develop chronic or progressive disease mainly due to pulmonary or cardiovascular complications that require long-term therapy. The diagnosis of sarcoidosis requires histopathological evidence of noncaseating granulomatous inflammation in one or more organs coupled with compatible clinical and radiological features and the exclusion of other causes of granulomatous inflammation; however, in the presence of typical disease manifestations such as Löfgren’s syndrome, Heerfordt’s syndrome, lupus pernio and asymptomatic bilateral and symmetrical hilar lymphadenopathy, the diagnosis can be established with high level of certainty on clinical grounds alone. This review critically examines the diagnostic approach to sarcoidosis and emphasizes the importance of a careful exclusion of alternative diagnoses.

Genetics in sarcoidosis

PURPOSE OF REVIEW

Epidemiological and clinical observations as well as familial clustering support the existence of a genetic predisposition to sarcoidosis. In this article, we review the most recent findings in genetics of sarcoidosis and discuss how the identification of risk alleles may help advancing our understanding of disease etiology and development.

RECENT FINDINGS

Genetic studies of sarcoidosis phenotypes have identified novel and ancestry-specific associations. Gene-environment interaction studies highlighted the importance of integrating genetic information when assessing the relationship between sarcoidosis and environmental exposures. A case-control-family study revealed that the heritability of sarcoidosis is only 49%, suggesting the existence of additional important contributors to disease risk. The application of whole-exome sequencing has identified associations with disease activity and prognosis. Finally, gene expression studies of circulating immune cells have identified shared and unique pathways between sarcoidosis and other granulomatous diseases.

SUMMARY

Sarcoidosis genetic research has led to the identification of a number of associations with both sarcoidoses per se and disease phenotypes. Newer sequencing technologies are likely to increase the number of genetic variants associated with sarcoidosis. However, studying phenotypically and ethnically homogeneous patient subsets remains critically important regardless of the genetic approach used.

Pulmonary granulomatosis of genetic origin

Granulomatous inflammation of the lung can be a manifestation of different conditions and can be caused by endogenous inflammation or external triggers. A multitude of different genetic mutations can either predispose patients to infections with granuloma-forming pathogens or cause autoinflammatory disorders, both leading to the phenotype of pulmonary granulomatosis. Based on a detailed patient history, physical examination and a diagnostic approach including laboratory workup, pulmonary function tests (PFTs), computed tomography (CT) scans, bronchoscopy with bronchoalveolar lavage (BAL), lung biopsies and specialised microbiological and immunological diagnostics, a correct diagnosis of an underlying cause of pulmonary granulomatosis of genetic origin can be made and appropriate therapy can be initiated. Depending on the underlying disorder, treatment approaches can include antimicrobial therapy, immunosuppression and even haematopoietic stem cell transplantation (HSCT). Patients with immunodeficiencies and autoinflammatory conditions are at the highest risk of developing pulmonary granulomatosis of genetic origin. Here we provide a review on these disorders and discuss pathogenesis, clinical presentation, diagnostic approach and treatment.

Pulmonary granulomatosis of genetic origin mostly occurs in immunodeficiency disorders and autoinflammatory conditions. In addition to specific approaches in this regard, the diagnostic workup needs to cover environmental and occupational aspects.https://bit.ly/31SqdHW

The pathogenesis and pathology of idiopathic pleuroparenchymal fibroelastosis

Idiopathic pleuroparenchymal fibroelastosis (IPPFE) is a rare subtype of idiopathic interstitial pneumonias that consists of elastofibrosis involving the lung parenchyma and pleural collagenous fibrosis predominantly located in the upper lobes. IPPFE has various distinct clinical and physiological characteristics, including platythorax and a marked decrease of forced vital capacity with an increased residual volume on a respiratory function test. The concept of IPPFE is now widely recognized and some diagnostic criteria have been proposed. In addition, the accumulation of cases has revealed the pathological features of IPPFE. However, little is known about the pathogenesis or the process of disease formation in IPPFE. This review article will provide a summary of the pathological features and previously reported hypotheses on disease formation in IPPFE, to discuss the potential etiologies and pathogenesis of IPPFE.

Malignant melanoma in situ associated with underlying sarcoidal granuloma: A histopathological mimicker of invasive epithelioid melanoma cells

Malignant melanoma is known to show diverse cellular morphologies, including a histiocyte-like morphology. Therefore, many non-melanocytic proliferations or infiltrates can mimic melanoma, and be confusing especially when they coexist with a true melanoma. Herein, we report an unusual case of a melanoma in situ with an underlying sarcoidal granuloma, which mimicked dermal invasion of melanoma. This case expands insight into non-neoplastic lesions closely mimicking melanoma.

Sarcoidosis exosomes stimulate monocytes to produce pro-inflammatory cytokines and CCL2

Pulmonary sarcoidosis has unknown etiology, a difficult diagnostic procedure and no curative treatment. Extracellular vesicles including exosomes are nano-sized entities released from all cell types. Previous studies of exosomes from bronchoalveolar lavage fluid (BALF) of sarcoidosis patients have revealed pro-inflammatory components and abilities, but cell sources and mechanisms have not been identified. In the current study, we found that BALF exosomes from sarcoidosis patients, but not from healthy individuals, induced a dose-dependent elevation of intracellular IL-1β in monocytes. Analyses of supernatants showed that patient exosomes also induced release of IL-1β, IL-6 and TNF from both PBMCs and enriched monocytes, suggesting that the observed effect is direct on monocytes. The potently chemotactic chemokine CCL2 was induced by exosomes from a subgroup of patients, and in a blocking assay the exosome-induced CCL2 was reduced for 13 out of 19 patients by the asthma drug Montelukast, a cysteinyl leukotriene receptor antagonist. Further, reactive oxygen species generation by PBMCs was induced to a higher degree by patient exosomes compared to healthy exosomes. These findings add to an emerging picture of exosomes as mediators and disseminators of inflammation, and open for further investigations of the link between CCL2 and exosomal leukotrienes in sarcoidosis.

Equine Idiopathic Systemic Granulomatous Disease With Manifestation in the Cerebellum Associated With Equid Gammaherpesvirus 2

Idiopathic systemic granulomatous disease (ISGD), also known as equine sarcoidosis is an uncommon disease of horses, manifesting in exfoliative dermatitis and granulomatous inflammation in various organs. The current report presents a case of a 15-year-old Hanoverian mare with a 4-month history of weight loss, recurrent fever, skin lesions, and movement disorders. Pathological examination revealed granulomatous and necrotizing inflammation in the skin, regional lymph nodes, and cerebellum. Based on histological, immunohistochemical, and microbiological findings, the diagnosis of ISGD was made. Sequencing of the polymerase chain reaction product of pooled brain tissue revealed the presence of equid gammaherpesvirus 2 DNA. This case is the first description of generalized ISGD with granulomatous dermatitis simultaneously affecting the skin and cerebellum.

Clinical Presentations, Pathogenesis, and Therapy of Sarcoidosis: State of the Art

Sarcoidosis is a systemic disease of unknown etiology characterized by the presence of noncaseating granulomas that can occur in any organ, most commonly the lungs. Early and accurate diagnosis of sarcoidosis remains challenging because initial presentations may vary, many patients are asymptomatic, and there is no single reliable diagnostic test. Prognosis is variable and depends on epidemiologic factors, mode of onset, initial clinical course, and specific organ involvement. From a pathobiological standpoint, sarcoidosis represents an immune paradox, where an excessive spread of both the innate and the adaptive immune arms of the immune system is accompanied by a state of partial immune anergy. For all these reasons, the optimal treatment for sarcoidosis remains unclear, with corticosteroid therapy being the current gold standard for those patients with significantly symptomatic or progressive pulmonary disease or serious extrapulmonary disease. This review is a state of the art of clinical presentations and immunological features of sarcoidosis, and the current therapeutic approaches used to treat the disease.

Sarcoidosis: Causes, Diagnosis, Clinical Features, and Treatments

Sarcoidosis is a multisystem granulomatous disease with nonspecific clinical manifestations that commonly affects the pulmonary system and other organs including the eyes, skin, liver, spleen, and lymph nodes. Sarcoidosis usually presents with persistent dry cough, eye and skin manifestations, weight loss, fatigue, night sweats, and erythema nodosum. Sarcoidosis is not influenced by sex or age, although it is more common in adults (< 50 years) of African-American or Scandinavians decent. Diagnosis can be difficult because of nonspecific symptoms and can only be verified following histopathological examination. Various factors, including infection, genetic predisposition, and environmental factors, are involved in the pathology of sarcoidosis. Exposures to insecticides, herbicides, bioaerosols, and agricultural employment are also associated with an increased risk for sarcoidosis. Due to its unknown etiology, early diagnosis and detection are difficult; however, the advent of advanced technologies, such as endobronchial ultrasound-guided biopsy, high-resolution computed tomography, magnetic resonance imaging, and 18F-fluorodeoxyglucose positron emission tomography has improved our ability to reliably diagnose this condition and accurately forecast its prognosis. This review discusses the causes and clinical features of sarcoidosis, and the improvements made in its prognosis, therapeutic management, and the recent discovery of potential biomarkers associated with the diagnostic assay used for sarcoidosis confirmation.

Sarcoidosis as an Autoimmune Disease

Despite the large number of performed studies, the etiology and pathogenesis of sarcoidosis still remain unknown. Most researchers allude to the possible autoimmune or immune-mediated genesis of the disease. This review attempts an integral analysis of currently available information suggesting an autoimmune genesis of sarcoidosis and is divided into four categories: the evaluation of clinical signs described both in patients with sarcoidosis and “classic” autoimmune diseases, the role of triggering factors in the development of sarcoidosis, the presence of immunogenic susceptibility in the development of the disease, and the analysis of cellular and humoral immune responses in sarcoidosis. Studying the etiology and pathogenesis of sarcoidosis will improve diagnostic procedures as well as the prognosis and patients' quality of life.

IL-13-regulated Macrophage Polarization during Granuloma Formation in an In Vitro Human Sarcoidosis Model

The mechanisms underlying abnormal granuloma formation in patients with sarcoidosis are complex and remain poorly understood. A novel in vitro human granuloma model was used to determine the molecular mechanisms of granuloma genesis in patients with sarcoidosis in response to putative disease-causing mycobacterial antigens. Peripheral blood mononuclear cells (PBMCs) from patients with active sarcoidosis and from normal, disease-free control subjects were incubated for 7 days with purified protein derivative-coated polystyrene beads. Molecular responses, as reflected by differential expression of genes, extracellular cytokine patterns, and cell surface receptor expression, were analyzed. Unbiased systems biology approaches were used to identify signaling pathways engaged during granuloma formation. Model findings were compared with human lung and mediastinal lymph node gene expression profiles. Compared with identically treated PBMCs of control subjects (n = 5), purified protein derivative-treated sarcoidosis PBMCs (n = 6) were distinguished by the formation of cellular aggregates resembling granulomas. Ingenuity Pathway Analysis of differential expression gene patterns identified molecular pathways that are primarily regulated by IL-13, which promotes alternatively activated (M2) macrophage polarization. M2 polarization was further demonstrated by immunohistochemistry performed on the in vitro sarcoidosis granuloma-like structures. IL-13-regulated gene pathways were confirmed in human sarcoidosis lung and mediastinal lymph node tissues. The in vitro human sarcoidosis granuloma model provides novel insights into early granuloma formation, particularly IL-13 regulation of molecular networks that regulate M2 macrophage polarization. M2 macrophages are predisposed to aggregation and multinucleated giant cell formation, which are characteristic features of sarcoidosis granulomas. Clinical trial registered with www.clinicaltrials.gov (NCT01857401).

Sarcoidosis

Sarcoidosis is an inflammatory disorder of unknown cause that is characterized by granuloma formation in affected organs, most often in the lungs. Patients frequently suffer from cough, shortness of breath, chest pain and pronounced fatigue and are at risk of developing lung fibrosis or irreversible damage to other organs. The disease develops in genetically predisposed individuals with exposure to an as-yet unknown antigen. Genetic factors affect not only the risk of developing sarcoidosis but also the disease course, which is highly variable and difficult to predict. The typical T cell accumulation, local T cell immune response and granuloma formation in the lungs indicate that the inflammatory response in sarcoidosis is induced by specific antigens, possibly including self-antigens, which is consistent with an autoimmune involvement. Diagnosis can be challenging for clinicians because of the potential for almost any organ to be affected. As the aetiology of sarcoidosis is unknown, no specific treatment and no pathognomic markers exist. Thus, improved biomarkers to determine disease activity and to identify patients at risk of developing fibrosis are needed. Corticosteroids still constitute the first-line treatment, but new treatment strategies, including those targeting quality-of-life issues, are being evaluated and should yield appropriate, personalized and more effective treatments.

Next-Generation Sequencing Based HLA Typing: Deciphering Immunogenetic Aspects of Sarcoidosis

Unraveling of the HLA-related immunogenetic basis of several immune disorders is complex due to the extensive HLA polymorphism and strong linkage-disequilibrium between HLA loci. A lack of in phase sequence information, a relative deficiency of high resolution genotyping including non-coding regions and ambiguous haplotype assignment make it difficult to compare findings across association studies and to attribute a causal role to specific HLA alleles/haplotypes in disease susceptibility and modification of disease phenotypes. Earlier, historical antibody and DNA-based methods of HLA typing, primarily of low resolution at antigen/alellic group levels, yielded "indicative" findings which were partially improved by high-resolution DNA-based typing. Only recently, next-generation sequencing (NGS) approaches based on deep-sequencing of the complete HLA genes combined with bioinformatics tools began to provide the access to complete information at an allelic level. Analyzing HLA with NGS approaches, therefore, promises to provide further insight in the etiopathogenesis of several immune disorders in which HLA associations have been implicated. These range from coeliac disease and rheumatological conditions to even more complex disorders, such as type-1 diabetes, systemic lupus erythematosus and sarcoidosis. A systemic disease of unknown etiology, sarcoidosis has previously been associated with numerous HLA variants and also other gene polymorphisms, often in linkage with the HLA region. To date, the biological significance of these associations has only partially been defined. Therefore, more precise assignments of HLA alleles/haplotypes using NGS approaches could help to elucidate the exact role of HLA variation in the multifaceted etiopathogenesis of sarcoidosis, including epigenetic mechanisms. NGS-based HLA analyses may be also relevant for defining variable clinical phenotypes and for predicting the disease course or the response to current/plausible novel therapies.

Sarcoid of the Upper Humerus Found Incidentally on MR Images Obtained for Work-Up of Rotator Cuff Tear Where Compromised Tissue Quality Was a Concern for Surgical Success

Sarcoidosis is an idiopathic systemic inflammatory disorder characterized histologically by noncaseating granulomas. The pathogenesis likely includes genetic, immunologic, and environmental factors. The lungs, skin, and eyes are most commonly affected. Although bone involvement is possible, sarcoidosis of the humerus is rare, with few cases reported. Furthermore, we are unaware of any reports of sarcoidosis of the upper humerus with a coexisting rotator cuff tear. We report the case of a 50-year-old female with sarcoidosis of the humerus and a coexisting tear of the supraspinatus tendon. Her medical history includes type 2 diabetes, depression, and fatigue. She had chronic shoulder pain that worsened after her dog jerked on the leash. Radiographs were grossly normal. Subsequent magnetic resonance imaging (MRI) demonstrated a possible small full-thickness rotator cuff tear. Multiple rounded lesions were also noted within the proximal humerus. A biopsy demonstrated noncaseating granulomas, confirming the diagnosis of sarcoidosis. There was concern that her sarcoid lesions would compromise bone quality, limiting options for surgical repair of her rotator cuff tear. However, it was determined that her lesion did not involve cortical bone, and surgery was performed. During surgery, the supraspinatus tendon was found to be partially torn and was treated with arthroscopic debridement and acromioplasty. An excellent result was ultimately achieved after her rheumatologist started adalimumab injections. This case demonstrates that there can be a rare incidental finding of osseous sarcoid lesions in the upper humerus where the bone might be compromised in the location of a planned rotator cuff repair.

A Circulating MicroRNA Signature Serves as a Diagnostic and Prognostic Indicator in Sarcoidosis

MicroRNAs (miRNAs) act as post-transcriptional regulators of gene expression. In sarcoidosis, aberrant miRNA expression may enhance immune responses mounted against an unknown antigenic agent. We tested whether a distinct miRNA signature functions as a diagnostic biomarker and explored its role as an immune modulator in sarcoidosis. The expression of miRNAs in peripheral blood mononuclear cells from subjects who met clinical and histopathologic criteria for sarcoidosis was compared with that observed in matched controls in the ACCESS (A Case Controlled Etiologic Study of Sarcoidosis) study. Signature miRNAs were determined by miRNA microarray analysis and validated by quantitative RT-PCR. Microarray analysis identified 54 mature, human feature miRNAs that were differentially expressed between the groups. Significant feature miRNAs that distinguished subjects with sarcoidosis from controls were selected by means of probabilistic models adjusted for clinical variables. Eight signature miRNAs were chosen to verify the diagnosis of sarcoidosis in a validation cohort, and distinguished subjects with sarcoidosis from controls with a positive predictive value of 88%. We identified both novel and previously described genes and molecular pathways associated with sarcoidosis as targets of these signature miRNAs. Additionally, we demonstrate that signature miRNAs (hsa-miR-150-3p and hsa-miR-342-5p) are significantly associated with reduced lymphocytes and airflow limitations, both of which are known markers of a poor prognosis. Together, these findings suggest that a circulating miRNA signature serves as a noninvasive biomarker that supports the diagnosis of sarcoidosis. Future studies will test the miRNA signature as a prognostication tool to identify unfavorable changes associated with poor clinical outcomes in sarcoidosis.

[Sarcoidosis and uveitis : An update]

Ocular involvement in sarcoidosis is present in up to one third of patients and is frequently manifested before the underlying systemic disease has been diagnosed. With a view to the therapeutic consequences an early diagnosis of the underlying disease is advantageous. In cases of visual loss early diagnostic measures include invasive procedures, such as ultrasound-guided bronchoalveolar lavage and transbronchial biopsy, if nodular conjunctival or cutaneous manifestations which would confirm the diagnosis are not present. Sufficiently sensitive biomarkers of disease activity have not yet been identified. As elevated activity of angiotensin-converting enzyme (ACE) and lysozyme are associated with disease activity they may be supportive of but not specific for the diagnosis. Other indicators include calcemia, calciuria, augmented activity of hepatic enzymes, cutaneous anergy and hilar changes in the lungs. In patients with newly diagnosed anterior uveitis presenting with granulomatous mutton-fat corneal precipitates, snow balls and vitreous body base condensates with mild retinal periphlebitis in intermediate uveitis as well as multifocal choroiditis (creamy choroidal lesions at different stages of activity and approximately 500 µm in diameter), a diagnosis of sarcoidosis has to be considered and tuberculosis should be excluded, even in the absence of a known systemic disease. Anterior uveitis is frequently a self-limiting condition, which can be well-controlled with topical steroids. On the other hand, intermediate, posterior and panuveitis are typically associated with a chronic course and require systemic therapy to prevent severe loss of vision. If the response to systemic corticosteroids is insufficient, treatment with immunomodulatory agents and biologics is initiated at progressively earlier stages, with a view to averting permanent organ damage and frequently with a positive impact on the short and long-term outcomes, even in therapy-refractive cases.

Sarcoidosis incidence and prevalence: a nationwide register-based assessment in Sweden

Our objective was to estimate the contemporary incidence and prevalence of sarcoidosis using Swedish population-based register data.Adults with any sarcoidosis-coded visit were identified from the National Patient Register (hospitalisations 1964-2013 and outpatient care 2001-2013). Demographic and medication dispensing data were retrieved from national registers. We estimated the prevalence of sarcoidosis in 2013 overall and by county of residence. The incidence of sarcoidosis during 2003-2012 was estimated by sex, age, education level and year of diagnosis. Case definitions were varied to test their robustness.More than 16 000 individuals had a history of sarcoidosis in 2013. When defined as two or more sarcoidosis-coded visits, the prevalence was 160 per 100 000. Using different definitions, the prevalence ranged from 152 (requiring a specialist visit) to 215 per 100 000 (only one visit required). The highest prevalence was observed in northern less densely populated counties. The incidence was 11.5 per 100 000 per year and varied by -10% to +30% depending on case definition. The incidence peaked in males aged 30-50 years and in females aged 50-60 years, but did not differ by education level and was stable over time.This study represents the largest epidemiological investigation of sarcoidosis using population-based individual-level data. Age at diagnosis in men was 10 years younger than in women and geographical variation was observed.