Clinical epidemiology of familial sarcoidosis: A systematic literature review

Whole exome sequencing of a German sarcoidosis family with four affected and one spontaneous remission case

OBJECTIVES

To analyse genetic mechanisms triggering familial sarcoidosis, whole exome screening of a family of six persons with four cases of sarcoidosis and two healthy controls was performed integrating progressive and spontaneous remission cases and evaluating involved genetic alterations that could potentially determine the individual course of the disease.

METHODS

Clinical diagnostic criteria in patients of the selected sarcoidosis family were according to American Thoracic Society/European Respiratory Society/World Association of Sarcoidosis and other Granulomatous Disorders guidelines. Exome screening of four patients and the two intrafamilial healthy relatives was performed by paired-end (2 × 100 bp) sequencing. We then selected the gene variants considered pathogenic on the basis of a series of prediction software applications and presence only in members of the family affected by sarcoidosis, after subtracting the common variations observed in healthy subjects.

RESULTS

Four persons out of six family members were affected by sarcoidosis. Fifty genes with uncommon in silico pathogenic variants could be identified that differentiated affected and healthy family members. One patient with sarcoidosis showed spontaneous remission whereas the remaining three patients required immunosuppressive treatment. Subtraction analysis revealed 18 genes that distinguished the three progressive cases from the patient with spontaneous remission.

CONCLUSION

The genetic analysis of these cases with familial sarcoidosis identified several involved genes and functional pathways that could help in understanding the basic mechanisms that determine the development of the disease and that discriminate spontaneously regressive and progressive forms.

Noninfectious Granulomatous Lung Disease: Radiological Findings and Differential Diagnosis

Granulomatous lung diseases (GLDs) are a heterogeneous group of pathological entities that can have different clinical presentations and outcomes. Granulomas are histologically defined as focal aggregations of activated macrophages, Langerhans cells, and lymphocytes, and may form in the lungs when the immune system cannot eliminate a foreign antigen and attempts to barricade it. The diagnosis includes clinical evaluation, laboratory testing, and radiological imaging, which especially consists of high-resolution computed tomography. bronchoalveolar lavage, transbronchial needle aspiration or cryobiopsy, positron emission tomography, while genetic evaluation can improve the diagnostic accuracy. Differential diagnosis is challenging due to the numerous different imaging appearances with which GLDs may manifest. Indeed, GLDs include both infectious and noninfectious, and necrotizing and non-necrotizing granulomatous diseases and the imaging appearance of some GLDs may mimic malignancy, leading to confirmatory biopsy. The purposes of our review are to report the different noninfectious granulomatous entities and to show their various imaging features to help radiologists recognize them properly and make an accurate differential diagnosis.

Establishing a Diagnosis of Pulmonary Sarcoidosis

Pulmonary sarcoidosis is the most prevalent manifestation of sarcoidosis and the commonest diagnosis in clinics for ILD. Due to the lack of a simple and reliable test, making the diagnosis is often challenging. There are three criteria that must always be considered: (1) compatible clinical presentation; (2) evidence of granuloma formation (usually non-caseating); and (3) exclusion of alternative causes of granulomatous disease. There are various tools available for diagnosis, amongst which serum biomarkers like sACE and sIL-2R, HRCT, BAL, EBUS/EUS and sometimes bronchoscopic or surgical lung biopsy are most contributive. However, the degree of invasiveness of the applied test and associated risk to the patient must be weighed against management consequences. In specific situations (e.g., presentation as Löfgren's syndrome) or when there is high suspicion based on HRCT in the context of supportive clinical findings, it might be justifiable to decide on a "working diagnosis of sarcoidosis" and to refrain from further invasive procedures for the patient. This should, however, preferably be agreed upon after discussion in an experienced multidisciplinary team and requires close follow-up of the patient. In general, it is advisable to always maintain a healthy dose of skepticism when making the diagnosis of sarcoidosis, especially when the clinical course of disease gives rise to this.

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.

European Respiratory Society statement on familial pulmonary fibrosis

Genetic predisposition to pulmonary fibrosis has been confirmed by the discovery of several gene mutations that cause pulmonary fibrosis. Although genetic sequencing of familial pulmonary fibrosis (FPF) cases is embedded in routine clinical practice in several countries, many centres have yet to incorporate genetic sequencing within interstitial lung disease (ILD) services and proper international consensus has not yet been established. An international and multidisciplinary expert Task Force (pulmonologists, geneticists, paediatrician, pathologist, genetic counsellor, patient representative and librarian) reviewed the literature between 1945 and 2022, and reached consensus for all of the following questions: 1) Which patients may benefit from genetic sequencing and clinical counselling? 2) What is known of the natural history of FPF? 3) Which genes are usually tested? 4) What is the evidence for telomere length measurement? 5) What is the role of common genetic variants (polymorphisms) in the diagnostic workup? 6) What are the optimal treatment options for FPF? 7) Which family members are eligible for genetic sequencing? 8) Which clinical screening and follow-up parameters may be considered in family members? Through a robust review of the literature, the Task Force offers a statement on genetic sequencing, clinical management and screening of patients with FPF and their relatives. This proposal may serve as a basis for a prospective evaluation and future international recommendations.

Renal sarcoidosis

Sarcoidosis is a systemic inflammatory disease of unknown etiology. The pathogenesis rests on an aberrant T cell response to unidentified antigens in individuals predisposed by genetic and environmental factors. Increased expression of polarized macrophages and disequilibrium between effector and regulator T cells contribute to the formation of noncaseating granulomas, that are frequently found in affected organs. The main kidney abnormalities in sarcoidosis are granulomatous interstitial nephritis (GIN) and hypercalcemia-related disorders. The clinical diagnosis is difficult. The outcome is variable, ranging from spontaneous remission to end-stage kidney disease (ESKD). Early diagnosis and prompt treatment with corticosteroids can improve the prognosis. Hypercalcemia may be responsible for acute kidney injury (AKI) caused by vasoconstriction of afferent arterioles. Complications of persistent hypercalcemia include nephrocalcinosis and renal stones. In patients with ESKD, dialysis and transplantation can offer results comparable to those observed in patients with other causes of kidney failure. Based on a review of the literature, we present an overview of the etiopathogenesis, the renal manifestations of sarcoidosis and their complications, management and prognosis.

Sarcoidosis beyond pulmonary involvement: A case series of unusual presentations

Unusual presentations of sarcoidosis pose a diagnostic challenge and warrant attention. Hematologic associations: Case 1 (37-years-old male): Pancytopenia: myelofibrosis (leading to sepsis and mortality) following a two-year quiescent course of biopsy-proven-sarcoidosis. Case 2: (38-years-old male): Presentation with thrombocytopenia (5 × 10³/cmm): immune thrombocytopenic purpura (histologically associated with megakaryocytic emperipolesis). Biopsied enlarged lymph nodes demonstrated sarcoidosis. Hematologic sarcoid involvement is usually due to granulomatous bone marrow (3.9%) or splenic infiltration (6–30%); however, the presented manifestations are scarcely reported with a potential significance that is yet to be elucidated. Case 3: Neurologic presentation: 48-years-old female: presentation with bilateral sensorineural hearing loss and facial palsy. Brain magnetic resonance imaging showed leptomeningeal thickening. Biopsied enlarged lymph nodes showed sarcoidosis. Case 4: Neurologic and renal manifestations: 13-years-old male (family history of sarcoidosis): Presenting with acute headache, investigations showed elevated serum creatinine (2.1 mg/dL) and angiotensin converting enzyme, and computed tomography chest and abdominal findings characteristic of sarcoidosis. Associated benign increased intracranial and acute tubulointerstitial nephritis (with eosinophils) were diagnosed upon concordant workup. Of sarcoidosis neurologic affection (5–10%), cranial nerve(s) involvement is among the most common (25–50% of neurosarcoid affection), particularly that of the facial nerve (Case 3). Leptomeningeal enhancement is among the most common neurosarcoid radiologic findings (30–40%). Whereas benign increased intracranial tension (Case 4) is much less reported. Among sarcoidosis renal involvement (35–50%), interstitial nephritis usually presents with granulomatous renal lesions, yet its sole association with sarcoidosis is unusual (Case 4). The portrayed atypical hematologic, neurologic, and renal manifestations further emphasize the masquerading nature of sarcoidosis.

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Although hematologic involvement in sarcoidosis is usually due to granulomatous infiltration of the bone marrow or spleen and/or hypersplenism, associations with hematologic neoplasms or myelodysplastic syndromes have been reported. However, coexisting myelofibrosis (presented in our first patient) is much less reported and raises interest.

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We present a patient with coexistent with ITP (case 2) that was further histologically associated with megakaryocytic emperipolesis. The significance of this association is yet to be elucidated.

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Cranial nerve(s) involvement is among the most widely neurosarcoid manifestations reported which was demonstrated in our third patient. Brain MRI showing evidence of leptomeningeal enhancement which is among the most common radiologic findings of neurosarcoidosis.

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A juvenile-onset patient with a family history of sarcoidosis manifested with benign increased intracranial tension (ICT) and renal affection in the form of tubulointerstitial nephritis. Unlike cranial nerve affection, benign ICT is a rarely reported neurosarcoid manifestation, and renal involvement is usually due to hypercalcemia or granulomatous involvement with or without tubulointerstitial nephritis.

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Although unusual presentations warrant attention as the pose a diagnostic and therapeutic challenge, they should be prudently interpreted.

Retrospective study of elderly onset sarcoidosis in Tunisian patients

BACKGROUND

Sarcoidosis is a systemic granulomatous disease of unknown etiology. It affects mostly young adults. In the elderly, the presentation of this disease is different, often posing positive diagnosis problems.

OBJECTIVES

We intend to describe the various clinical features and the management of sarcoidosis in elderly patients (age ≥65 years) compared to the younger ones.

METHODS

We performed a retrospective, descriptive and comparative study in the Department of Internal Medicine in the University Hospital Hedi Chaker, Sfax, Tunisia, between 1996 and 2016.

RESULTS

From a series of 80 patients, we found sixteen patients (20%) with sarcoidosis diagnosed after the age of 65 years. A female preponderance (81,25%) was noted. Intrathoracic involvement concerned 13 patients (81,3%). Extrapulmonary signs were also frequent (93,8%). The main extrathoracic manifestations were ganglionar involvement (75%), an alteration of the general health (31,3%), hepatic involvement (31,3%), cutaneous involvement (25%) and ocular involvement (25%). Biological manifestations were hypercalcemia, hypercalciuria, lymphopenia and hypergammaglobulinemia noted in respectively 12,5%, 12,5%, 31,3% and 50% of the cases. Angiotensin-converting enzyme(ACE) level was elevated in 100% of the patients. Lymphadenopathy and cutaneous biopsies were important contributing factors to diagnosis (respectively: 100% and 75% were positive). Oral corticosteroid therapy was required in 50% of cases. Evolution was marked by pulmonary fibrosis in two cases. Satisfactory course of the disease was observed in the other patients.

CONCLUSION

Young and elderly subjects had common characteristics of sarcoidosis, except for more coexisting chronic morbidities, no erythema nodosum and more frequent high levels of ACE in the elderly group.

Novel ACE mutations mimicking sarcoidosis by increasing blood ACE levels

An elevated blood angiotensin I-converting enzyme (ACE) supports diagnosis of sarcoidosis and Gaucher disease. However, some ACE mutations increase ACE shedding, and patients with these mutations are therefore at risk of being incorrectly diagnosed with sarcoidosis because of elevated serum ACE levels. We applied a novel approach called "ACE phenotyping" to identify possible ACE mutations in 3 pulmonary clinic patients that had suspected sarcoidosis based on elevated blood ACE levels. Conformational fingerprinting of ACE indicated that these mutations may be localized in the stalk region of the protein and these were confirmed by whole exome sequencing. Index patient 1 (IP1) had a mutation (P1199L) that had been previously identified, while the other 2 patients had novel ACE mutations. IP2 had 2 mutations, T887M and N1196K (eliminating a putative glycosylation site), while IP3 had a stop codon mutation Q1124X (eliminating the transmembrane anchor). We also performed a comprehensive analysis of the existing database of all ACE mutations to estimate the proportion of mutations increasing ACE shedding. The frequency of ACE mutations resulting in increased blood ACE levels may be much higher than previously estimated. ACE phenotyping, together with whole exome sequencing, is a diagnostic approach that could prevent unnecessary invasive and/or costly diagnostic procedures, or potentially harmful treatment for patients misdiagnosed on the basis of elevated blood ACE levels.

High expression of mTOR signaling in granulomatous lesions is not predictive for the clinical course of sarcoidosis

INTRODUCTION

Sarcoidosis is a systemic granulomatous disease with a variable clinical presentation and disease course. There is still no reliable biomarker available, which assists in the diagnosis or prediction of the clinical course. According to a murine model, the expression level of the metabolic checkpoint kinase mechanistic target of Rapamycin complex 1 (mTORC1) in granulomas of sarcoidosis patients may be used as a clinical biomarker.

MATERIAL AND METHODS

This is a retrospective analysis of 58 patients with histologically confirmed sarcoidosis. Immunohistochemical staining of granulomas from tissue samples was evaluated for the expression of activated mTORC1 signaling, including phosphorylated mTOR, its downstream effectors S6K1, 4EBP1 and the proliferation marker Ki-67. Patients were categorized according to different clinical phenotypes, serum biomarkers, and immunomodulatory therapy.

RESULTS

All patients showed activated mTORC1 signaling in granulomas, which correlated with its downstream effectors S6K1 and 4EBP1 but was not related to Ki-67 expression. The mTORC1 activity revealed an association neither to disease severity nor the necessity of treatment; however, p-mTOR inversely correlated with cumulative corticosteroid dosage.

CONCLUSION

Our data confirm activation of the mTORC1 pathway in sarcoidosis, supporting the hypothesis that mTOR is a significant driver in granuloma formation. However, we could not find a relationship between the degree of mTOR activation and disease severity or the need for therapy.

Recent advances in sarcoidosis genomics: epigenetics, gene expression, and gene by environment (G × E) interaction studies

PURPOSE OF REVIEW

We aim to review the most recent findings in genomics of sarcoidosis and highlight the gaps in the field.

RECENT FINDINGS

Original explorations of sarcoidosis subphenotypes, including cases associated with the World Trade Center and ocular sarcoidosis, have identified novel risk loci. Innovative gene--environment interaction studies utilizing modern analytical techniques have discovered risk loci associated with smoking and insecticide exposure. The application of whole-exome sequencing has identified genetic variants associated with persistent sarcoidosis and rare functional variations. A single epigenomics study has provided background knowledge of DNA methylation mechanisms in comparison with gene expression data. The application of machine-learning techniques has suggested new drug repositioning for the treatment of sarcoidosis. Several gene expression studies have identified prominent inflammatory pathways enriched in the affected tissue.

SUMMARY

Certainly, sarcoidosis research has recently advanced in the exploration of disease subphenotypes, utilizing novel analytical techniques, and including measures of clinical variation. Nevertheless, large-scale and diverse cohorts investigated with advanced sequencing methods, such as whole-genome and single-cell RNA sequencing, epigenomics, and meta-analysis coupled with cutting-edge analytic approaches, when employed, will broaden and translate genomics findings into clinical applications, and ultimately open venues for personalized medicine.

Current Insights in Genetics of Sarcoidosis: Functional and Clinical Impacts

Sarcoidosis is a complex disease that belongs to the vast group of autoinflammatory disorders, but the etiological mechanisms of which are not known. At the crosstalk of environmental, infectious, and genetic factors, sarcoidosis is a multifactorial disease that requires a multidisciplinary approach for which genetic research, in particular, next generation sequencing (NGS) tools, has made it possible to identify new pathways and propose mechanistic hypotheses. Codified treatments for the disease cannot always respond to the most progressive forms and the identification of new genetic and metabolic tracks is a challenge for the future management of the most severe patients. Here, we review the current knowledge regarding the genes identified by both genome wide association studies (GWAS) and whole exome sequencing (WES), as well the connection of these pathways with the current research on sarcoidosis immune-related disorders.

Genetic Basis of Myocarditis: Myth or Reality?

The genetic basis of myocarditis remains an intriguing concept, at least as long as the definition of myocarditis constitutes the definitive presence of myocardial inflammation sufficient to cause the observed ventricular dysfunction in the setting of cardiotropic infections. Autoimmune or immune-mediated myocardial inflammation constitutes a complex area of clinical interest, wherein numerous and not yet fully understood role of hereditary auto-inflammatory diseases can result in inflammation of the pericardium and myocardium. Finally, myocardial involvement in hereditary immunodeficiency diseases, cellular and humoral, is a possible trigger for infections which may complicate the diseases themselves. Whether the role of constitutional genetics can make the patient susceptible to myocardial inflammation remains yet to be explored.

Clustering of immune-mediated diseases in sarcoidosis

PURPOSE OF REVIEW

Sarcoidosis is an immune-mediated disease of unknown cause. Immune-mediated diseases appear to cluster in patients and in families. We review what is known on this topic for sarcoidosis, and what factors may underlie disease clustering.

RECENT FINDINGS

In populations of patients with sarcoidosis, relative risk estimates of Sjögren's syndrome, systemic lupus erythematosus, autoimmune hepatitis, ankylosing spondylitis, multiple sclerosis (MS), celiac disease, autoimmune thyroid disease, and ulcerative colitis, varied between 2.1 and 11.6. In relatives of patients with sarcoidosis, relative risk estimates varied between 1.3 and 5.8 for sarcoidosis, MS, celiac disease, type 1 diabetes, Graves' disease, rheumatoid arthritis, Crohn's disease, and ulcerative colitis. Shared risk loci in key immunological pathways provide evidence for a contribution to development of multiple diseases. Identical changes in the immune status, epigenetic alterations, and environmental triggers have been detected in several diseases, and drug-induced disease is likely responsible for a small portion of co-occurring disease.

SUMMARY

Clustering of sarcoidosis and other immune-mediated diseases in patients and in their relatives occurs for sarcoidosis, MS, celiac disease, Graves' disease, and ulcerative colitis. Further research is needed to substantiate causal links and risk estimates in patients and their relatives.