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Behçet’s disease (BD) is a systemic inflammatory disease with unknown etiology. It is characterized by recurrent mucocutaneous lesions and major organ disease such as ocular, neurologic, vascular, and gastrointestinal manifestations. The diagnosis of BD is mainly based on clinical manifestations after ruling out other potential causes. There are no specific laboratory, histopathologic, or genetic findings for the diagnosis of BD. The International Study Group (ISG) criteria set is still the most widely used set for the diagnosis. The main limitation of this criteria set is the lack of major organ manifestations such as vascular, neurologic, and gastrointestinal involvement. The ICBD 2014 criteria are more sensitive, especially in early disease. However, patients with such as spondyloarthritis can easily meet this criteria set, causing overdiagnosis. Diagnosing BD can be a big challenge in daily practice, especially in patients presenting with only major organ involvement such as posterior uveitis, neurologic, vascular, and gastrointestinal findings with or without oral ulcers. These patients do not meet ISG criteria and can be diagnosed with “expert opinion” in countries with high BD prevalence. The pathergy test is the only diagnostic test used as diagnostic or classification criteria for BD. Our recent studies showed that common femoral vein (CFV) thickness measurement can be a valuable, practical, and cheap diagnostic tool for BD with sensitivity and specificities higher than 80% for the cut-off value of 0.5 mm. However, the diagnostic accuracy of CFV measurement should be investigated in other disease groups in the differential diagnosis of BD and in also different ethnic populations.

Environmental and other triggering factors are suggested to cause the onset and the clinical relapses of Behçet’s syndrome (BS), a multi-systemic inflammatory disorder. In this review, environmental factors are discussed according to their interactions with etiopathogenesis, immune response and disease activity. Stress is a common self-triggering factor for most BS patients. Stimuli such as some foods can activate oral ulcers, and may be linked to the histamine content of the food. Oral/skin trauma and menstruation associated with hormonal factors aggravate, whereas allergy/atopy seem to alleviate the symptoms of BS. Infections are associated with BS, and microbial stimuli can activate inflammation in mucosal surfaces with increased Th1/Th17 responses. Fecal and oral microbiome patterns change in diversity and composition in BS. Better oral hygiene applications and anti-microbial interventions might be helpful to suppress oral ulcers in BS.

ObjectivesTo update the EULAR recommendations for the use of imaging modalities in primary large vessel vasculitis (LVV).MethodsA systematic literature review update was performed to retrieve new evidence on ultrasound, MRI, CT and [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) for diagnosis, monitoring and outcome prediction in LVV. The task force consisted of 24 physicians, health professionals and patients from 14 countries. The recommendations were updated based on evidence and expert opinion, iterating until voting indicated consensus. The level of agreement was determined by anonymous votes.ResultsThree overarching principles and eight recommendations were agreed. Compared to the 2018 version, ultrasound is now recommended as first-line imaging test in all patients with suspected giant cell arteritis, and axillary arteries should be included in the standard examination. As an alternative to ultrasound, cranial and extracranial arteries can be examined by FDG-PET or MRI. For Takayasu arteritis, MRI is the preferred imaging modality; FDG-PET, CT or ultrasound are alternatives. Although imaging is not routinely recommended for follow-up, ultrasound, FDG-PET or MRI may be used for assessing vessel abnormalities in LVV patients with suspected relapse, particularly when laboratory markers of inflammation are unreliable. MR-angiography, CT-angiography or ultrasound may be used for long-term monitoring of structural damage, particularly at sites of preceding vascular inflammation.ConclusionsThe 2023 EULAR recommendations provide up-to-date guidance for the role of imaging in the diagnosis and assessment of patients with LVV.

This article presents the concept that Behçet disease and several spondyloarthropathies might have a common immunopathogenetic basis. The authors propose that barrier dysfunction in environmentally exposed organs, and aberrant innate immune reactions at sites of mechanical stress, trigger secondary adaptive immune CD8 + T-cell responses characterized by prominent neutrophilic inflammation. The differential immunopathology of these 'MHC-I-opathies' could reflect antigenic differences in target tissues. The spondyloarthropathies comprise ankylosing spondylitis (AS), reactive arthritis, psoriatic arthritis (PsA) and arthritis associated with inflammatory bowel disease. In this Perspectives article, we describe how Behçet disease and several clinically distinct spondyloarthropathies—all associated with MHC class I (MHC-I) alleles such as HLA-B * 51 , HLA-C * 0602 and HLA-B * 27 and epistatic ERAP-1 interactions—have a shared immunopathogenetic basis. As a unifying concept, we propose that barrier dysfunction in environmentally exposed organs such as the skin, and aberrant innate immune reactions at sites of mechanical stress, can often trigger secondary adaptive immune CD8 + T-cell responses with prominent neutrophilic inflammation that culminate in exacerbation and recurrence of these diseases. Of note, these 'MHC-I-opathies' show a differential immunopathology, probably reflecting antigenic differences within target tissues: HLA-B * 51 is linked to ocular and mucocutaneous disease but not gut involvement, and HLA-C * 0602 is linked to type I psoriasis but not scalp or nail disease.

To develop evidence-based recommendations for the use of imaging modalities in primary large vessel vasculitis (LVV) including giant cell arteritis (GCA) and Takayasu arteritis (TAK). European League Against Rheumatism (EULAR) standardised operating procedures were followed. A systematic literature review was conducted to retrieve data on the role of imaging modalities including ultrasound, MRI, CT and [18F]-fluorodeoxyglucose positron emission tomography (PET) in LVV. Based on evidence and expert opinion, the task force consisting of 20 physicians, healthcare professionals and patients from 10 EULAR countries developed recommendations, with consensus obtained through voting. The final level of agreement was voted anonymously. A total of 12 recommendations have been formulated. The task force recommends an early imaging test in patients with suspected LVV, with ultrasound and MRI being the first choices in GCA and TAK, respectively. CT or PET may be used alternatively. In case the diagnosis is still in question after clinical examination and imaging, additional investigations including temporal artery biopsy and/or additional imaging are required. In patients with a suspected flare, imaging might help to better assess disease activity. The frequency and choice of imaging modalities for long-term monitoring of structural damage remains an individual decision; close monitoring for aortic aneurysms should be conducted in patients at risk for this complication. All imaging should be performed by a trained specialist using appropriate operational procedures and settings. These are the first EULAR recommendations providing up-to-date guidance for the role of imaging in the diagnosis and monitoring of patients with (suspected) LVV.

Historically inflammation against self was considered autoimmune which stems back to the seminal observations by Ehrlich who described serum factors, now known to be autoantibodies produced by B lineage cells that mediate “horror autotoxicus”. The 20 th century elucidation of B- and T-cell adaptive immune responses cemented the understanding of the key role of adaptive immune responses in mediating pathology against self. However, Mechnikov shared the Nobel Prize for the discovery of phagocytosis, the most rudimentary aspect of innate immunity. Fast forward some 100 years and an immunogenetic understanding of innate immunity led to the categorising of innate immunopathology under the umbrella term ‘auto inflammation’ and terminology such as “horror autoinflammaticus” to highlight the schism from the classical adaptive immune understanding of autoimmunity. These concepts lead to calls for a two-tiered classification of inflammation against self, but just as innate and adaptive immunity are functionally integrated, so is immunopathology in many settings and the concept of an autoimmune to autoinflammation continuum emerged with overlaps between both. Herein we describe several historically designated disorders of adaptive immunity where innate immunity is key, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still's disease (AOSD) where the immunopathology phenotype is strongly linked to major histocompatibility complex (MHC) class II associations and responds to drugs that target T-cells. We also consider MHC-I-opathies including psoriasis and Behcet's disease(BD) that are increasingly viewed as archetype CD8 T-cell related disorders. We also briefly review the key role of barrier dysfunction in eczema and ulcerative colitis (UC) where innate tissue permeability barrier dysfunction and microbial dysbiosis contributes to prominent adaptive immune pathological mechanisms. We also highlight the emerging roles of intermediate populations of lymphocytes including gamma delta (γδ) and mucosal-associated invariant T (MAIT) cells that represent a blend of adaptive immune plasticity and innate immune rapid responders that may also determine site specific patterns of inflammation.

Behçet's syndrome (BS) is a rare systemic vasculitis, characterized by a wide range of different clinical involvements and unpredictable phases of recurrence and remission. BS can be described as a multifactorial disease with an incompletely known etiopathogenesis; in fact, though presenting some peculiar features, such as its typical geographic distribution and the strong association with the well-known genetic predisposing factor HLA-B * 51, the cause behind the onset and progression of the disease remains currently not fully understood. Besides genetic HLA and non-HLA predisposing associations and epigenetic influence, environmental factors also play an important role in the pathogenesis of the disease, and among these, infectious agents (both bacterial and viral) and specific microbiome alterations are considered of particular relevance in BS pathogenesis. BS has been included for decades among autoimmune diseases, in light of evidence showing T- and B-cell aberrant responses. However, because of recurrent mucocutaneous lesions and episodes of inflammation without antigen-specific T-cell or autoantibody responses, BS has also been classified among autoinflammatory disorders. Nevertheless, differently from autoinflammatory diseases, BS mildly responds to therapies targeting IL-1, its onset is not usually in childhood, and has high neutrophilic vasculitic involvement. Finally, given the association with HLA class I alleles, similar to spondyloarthropathies, the concept of BS as a major histocompatibility complex (MHC) I -opathy has been introduced. Understanding the complex etiopathogenesis of BS is essential to identify modifiable risk factors of BS occurrence or exacerbation and to develop targeted therapies. This review summarizes current evidence on the main genetic, environmental and immunological factors contributing to BS development.

The triggering receptor expressed on myeloid cells 1 (TREM-1) and peptidoglycan recognition protein 1 (PGLYRP1) are involved in the propagation of inflammatory responses. This study investigated whether serum levels of TREM-1 and PGLYRP1 correlate with periodontitis in rheumatoid arthritis (RA) patients. A total of 154 non-smoking participants with RA (n = 55, F/M: 41/14), Behçet´s disease (BD, n = 41, F/M: 30/11) and healthy controls (HC, n = 58, F/M: 40/18) were recruited. Serum and saliva were collected, the 28-joint disease activity score (DAS-28) was calculated and dental/periodontal measurements were recorded. Serum TREM-1 and PGLYRP1 levels were measured by ELISA and salivary bacterial DNA counts by quantitative polymerase chain reaction. TREM-1 and PGLYRP1 levels were higher in RA (166.3 ± 94.3; 155.5 ± 226.9 pg/ml) than BD (102.3 ± 42.8; 52.5 ± 26.3 pg/ml) and HCs (89.8 ± 55.7; 67.4 ± 37.3 pg/ml) (p < 0.05). In RA, periodontitis was associated with increased TREM-1 and PGLYRP1 levels (p < 0.05), yet in patients under methotrexate TREM-1 levels were lower. TREM-1 correlated with C-reactive protein (CRP) levels, DAS-28 and erythrocyte sedimentation rate, whereas PGLYRP1 positively correlated with CRP. RA patients displayed 3.5-fold higher salivary bacterial DNA counts than HCs. Increased serum TREM-1 levels correlated with PGLYRP1, CRP and DAS-28-ESR in RA patients with periodontitis.

Vascular involvement, especially in young males, is seen in up to 40% of the patients with Behcet’s disease (BD) and is a major cause of mortality and morbidity. In this study, we investigated vessel wall thickness (VWT) and dilatation in lower extremity veins with Doppler ultrasound (US) in male BD patients. Sixty-one male patients with BD, 37 healthy male controls (HC) and 27 male patients, with ankylosing spondylitis (AS), were included in the study. Venous Doppler US was performed by an experienced radiologist blinded to cases. Bilateral common femoral vein (CFV) wall thickness and great/small saphenous vein (SV) dilatations were assessed. All venous measurements were significantly higher in BD compared to AS and HC (p < 0.001 for all). Both right and left extremity CFV thicknesses had a high area under the ROC curve (> 0.8). Cut-off values for right and left CFV thicknesses for BD was 0.49 and 0.48 mm, respectively. High sensitivity and specificities are observed for both measurements (right CFV: sensitivity 81%, specificity 78.4%; left CFV: sensitivity 82.8%, specificity 81.1%). We found increased CFV thickness in BD patients independent of vascular involvement. As a similar change was not observed in controls, increased CFV thickness may be a specific sign of venous inflammation in BD. Our acceptable sensitivity and specificity values of CFV measurements suggest that assessment of femoral vein thickness with US may be a candidate diagnostic tool, especially in young males suspected of BD.

BackgroundsBehçet’s disease (BD) and Crohn’s disease (CD) cannot be easily differentiated in young adults presenting with nonspecific gastrointestinal (GI) manifestations due to similar extraintestinal manifestations. We recently showed that increased common femoral vein (CFV) thickness is a distinctive feature of BD, rarely present in other inflammatory or vascular diseases with a specificity higher than 80% for the cutoff value of ≥ 0.5 mm. We suggest that CFV thickness measurement with ultrasonography (US) can be a diagnostic tool for BD.AimsTo assess the diagnostic performance of CFV thickness measurement in the differential diagnosis of BD and CD.MethodsPatients with BD (n = 69), CD (n = 38), and healthy controls (HC) (n = 38) were included in the study. Bilateral CFV thickness was measured with Doppler US.ResultsBoth right and left CFV thicknesses were significantly higher in BD compared to HC and CD (for right: 0.76 mm vs 0.33 mm, for left: 0.78 mm vs 0.35 mm, p < 0.001 for both). CFV thicknesses in CD were similar to HC (p > 0.05 for both). CFV thickness was also similar between BD patients with and without GI involvement (p = 0.367). The diagnostic cutoff values of ≥ 0.5 mm for CFV thickness performed well against to both CD and HCs for discrimination of BD. The sensitivity and specificity rates were > 85% for both HC and CD. Positive and negative predictive values in our tertiary clinical setting were > 90%.ConclusionWe found significantly lower CFV thickness in CD compared to BD. Our results suggest that CFV wall thickness measurement is a distinctive diagnostic tool for the differentiation of BD and CD and can be helpful in daily practice for the differentiation of two diseases.