Secretion of mitochondrial DNA via exosomes promotes inflammation in Behçet's syndrome.

Mitochondrial DNA (mtDNA) leakage into the cytoplasm can occur when cells are exposed to noxious stimuli. Specific sensors recognize cytoplasmic mtDNA to promote cytokine production. Cytoplasmic mtDNA can also be secreted extracellularly, leading to sterile inflammation. However, the mode of secretion of mtDNA out of cells upon noxious stimuli and its relevance to human disease remain unclear. Here, we show that pyroptotic cells secrete mtDNA encapsulated within exosomes. Activation of caspase-1 leads to mtDNA leakage from the mitochondria into the cytoplasm via gasdermin-D. Caspase-1 also induces intraluminal membrane vesicle formation, allowing for cellular mtDNA to be taken up and secreted as exosomes. Encapsulation of mtDNA within exosomes promotes a strong inflammatory response that is ameliorated upon exosome biosynthesis inhibition in vivo. We further show that monocytes derived from patients with Behçet's syndrome (BS), a chronic systemic inflammatory disorder, show enhanced caspase-1 activation, leading to exosome-mediated mtDNA secretion and similar inflammation pathology as seen in BS patients. Collectively, our findings support that mtDNA-containing exosomes promote inflammation, providing new insights into the propagation and exacerbation of inflammation in human inflammatory diseases.

Comprehensive analysis of T-cell receptor repertoires reveals antigen-driven T-cell clusters in patients with Behçet's syndrome.

T lymphocytes are the major components of adaptive immunity in Behçet's syndrome (BS) pathology. However, the precise mechanism of T-cell-induced inflammatory condition remains to be determined. We applied bulk sequencing of the T-cell receptor (TCR) ß chain in peripheral blood samples from 45 patients with BS and 10 healthy donors as controls. TCR repertoires in BS patients displayed more clonality and less diversity than in healthy donors. Male patients exhibited lower diversity metrics of TCR and had a larger proportion in the top 10 clones than females (p = 0.016). There were no TCR clonality differences in other clinical features, such as age, disease duration, organ involvement, disease severity, and activity. By "Grouping of Lymphocyte Interactions by Paratope Hotspots" (GLIPH2) for antigen prediction, we found distinct 2477 clusters of TCR-ß sequences that potentially recognize similar antigens shared between BS patients. We observed clonal T-cell expansion in BS patients. Sexual differences in TCR clonal expansion and public TCR groups deserve further study to reveal the underline T-cell-mediated immunity in BS.

De novo manifestations during adalimumab treatment in Behçet's syndrome.

OBJECTIVES: Treatment response may be variable across organ manifestations of Behçet syndrome (BS). We aimed to determine the frequency of de novo manifestations during adalimumab treatment. METHODS: We conducted a chart review of all BS patients who received adalimumab in our center between 2008 and 2023. Demographic data, reasons for initiating adalimumab, concurrent medications, previous treatments, and outcomes were recorded. We defined de novo manifestations as new BS manifestations that occurred for the first time during treatment with adalimumab. For patients with vascular involvement, a new vascular event at another vessel was also considered as a de novo manifestation. RESULTS: Among the 335 patients, a de novo manifestation developed in 14 (4%) patients. De novo manifestations were vascular involvement in 5 patients, arthritis in 3, anterior uveitis in 2, nervous system involvement in 2, gastrointestinal involvement in 1, and epididymitis in 1 patient. The primary reasons for adalimumab treatment were vascular involvement in 5 patients, uveitis in 4, arthritis in 3, mucocutaneous involvement in 1, and epididymitis in 1 patient. Upon the development of de novo manifestation, adalimumab was switched to another biologic in 4 patients, dose was intensified in 3, colchicine, conventional immunosuppressives, and/or glucocorticoids were added in 5, and topical eye drops were added in 2 patients, leading to remission of de novo manifestations in all patients. CONCLUSION: De novo manifestations were infrequent (4%) among BS patients treated with adalimumab. Of these, 57% were major organ involvement, mainly vascular involvement. None of the patients developed posterior uveitis.

Validation of the Behçet's Syndrome Overall Damage Index (BODI) for Retrospective Studies and a Proposal for Modification.

OBJECTIVE: Assessment of damage accrual over time is important for evaluating and comparing long-term results of treatment modalities and strategies. Retrospective studies may be useful for assessing long-term damage, especially in rare diseases. We aimed to validate Behçet's Syndrome Overall Damage Index (BODI) for use in retrospective studies by evaluating its construct validity, reliability, and feasibility in retrospectively collected data. Additionally, we aimed to determine missing items by evaluating Behçet's syndrome patients with different types of organ involvement and long-term follow-up. METHODS: We included 300 patients who had at least 2 clinic visits at 1-year intervals. The construct validity for use in retrospective trials was assessed by comparing BODI scores calculated from patient charts and during face-to-face visits. BODI was additionally scored using retrospective chart data by 2 different observers and by the same observer six months apart, in a blinded manner. The time for filling BODI was evaluated to assess feasibility. Additionally, damaged items that were missing from BODI were identified. RESULTS: There was a good correlation between the retrospective and face-to-face evaluation of BODI (ICC 0.99; %95 CI 0.99-0.99). Inter-observer and intra-observer agreement were good (ICC 0.96 and 1, respectively). The main damage items that BODI did not capture were hypertension, liver failure, lung parenchymal involvement, glaucoma, and lymphedema. CONCLUSION: BODI seems to be a reliable and feasible instrument for assessing damage in retrospective studies. Modifying BODI using the additional damage items identified in this study may make it an even better scale.

HLA-B5 prevalence in patients with spondyloarthritis and impact on disease phenotype: a multicentric case-control study.

OBJECTIVE: The study aimed to estimate the prevalence of HLA-B51 and HLA-B52 in Lebanese patients with spondyloarthritis (SpA) compared to healthy controls (HC). We further aimed to evaluate the impact of HLA-B51 on phenotype and identify the distribution of the alleles in the HLA-B locus. METHODS: A case-control study enrolled consecutive SpA patients from three rheumatology clinics in Lebanon, including axial (axSpA), peripheral SpA (pSpA), and psoriatic arthritis (PsA) and HC from blood donors. Demographic and disease data were collected through interviews and file reviews, with testing of the entire HLA-B locus using molecular techniques. The prevalence of HLA-B51 and B52 was estimated in SpA patients versus controls. Prevalence comparisons were made, and logistic regression identified factors associated with HLA-B51 in patients. RESULTS: Data from 120 HC and 86 SpA patients (65 axSpA, 15 pSpA, 6 PsA), mean age 25.6 and 46.4 years, respectively, showed a higher HLA-B51 prevalence in SpA (25.6%), especially axSpA (29.2%) versus HC (12.5%), p = 0.016, and a numerically higher HLA-B52 prevalence (8.1% versus 4.2%, p = 0.230). HLA-B51 correlated with recurrent oral ulcerations (OR 7.99(95%CI 2.14-29.84) and radiographic juxta-articular erosions (OR 7.65(95%CI 1.14-38.03)). HLA-B35 was the most dominant allele in both groups (18.7%), followed by HLA-B27 (15.7%) and HLA-B51 (13.4%) in SpA. CONCLUSION: HLA-B51 was identified more frequently in patients with SpA compared to HC and was associated with recurrent oral ulcerations and juxta-articular radiographic erosions. Longitudinal studies are needed to determine whether this association indicates a disease overlap or might correlate with a specific SpA phenotype.

Disease and Treatment-Specific Complications of Behçet Syndrome.

PURPOSE OF REVIEW: We aimed to highlight disease-related and treatment-related complications of Behçet syndrome (BS) based on previous and recent studies and our own experience. RECENT FINDINGS: The Behçet's Disease Overall Damage Index is a newly developed instrument to assess damage in BS. Validation studies showed that damage is already present in some patients at diagnosis and continues to progress during the follow-up, mainly related to treatment complications. Nervous system and eye involvement are important causes of long-term disability. Cyclophosphamide seems to be associated with infertility and an increased risk of malignancies among BS patients, prompting the consideration of shortening the treatment duration. Flares in mucocutaneous manifestations have been reported with tocilizumab, and de novo BS manifestations with secukinumab therapy. Earlier diagnosis and treatment are essential to prevent disease-related damage in BS. Treatment-related complications seem to be the leading cause of damage during the disease course.

Impact of age at diagnosis on long-term prognosis in patients with intestinal Behçet's disease.

BACKGROUND AND AIM: Although age at disease onset is considered to be a significant factor in the prognosis of Crohn's disease, little is known about its influence on the long-term prognosis of those with intestinal Behçet's disease (BD). This study aimed to evaluate the long-term clinical outcomes of patients with intestinal BD according to age of disease onset. METHODS: Patients diagnosed with intestinal BD at < 18, 18-60, and > 60 years of age were classified into early-onset, adult-onset, and late-onset groups, respectively. The influence of disease onset time on clinical prognosis, including specific medical requirements, BD-related intestinal surgery, hospitalization, and emergency room visits, was compared using the log-rank test in a large cohort of patients with intestinal BD. RESULTS: Among 780 patients, 21 (2.7%), 672 (86.2%), and 87 (11.1%) comprised the early-onset, adult-onset, and late-onset groups, respectively. Patients in the early-onset group were more likely to require immunosuppressants than those in the adult-onset group (P = 0.048). Nine (42.9%), 158 (23.5%), and 18 (20.7%) patients in the early-onset, adult-onset, and late-onset groups, respectively, underwent intestinal resection. The early-onset group exhibited a higher risk for intestinal resection than the late-onset (P = 0.043) and adult-onset (P = 0.030) groups. The late-onset group exhibited a higher risk for BD-related hospitalization than the adult-onset group (P = 0.023). CONCLUSIONS: Age at diagnosis affected the clinical course of intestinal BD, including intestinal surgery, hospitalization, and specific medical requirements. Different treatment strategies should be established according to age at diagnosis.

Cerebral infarction in Behçet's syndrome caused by obliterative focal arteritis.

We present a case in which cerebral infarction was seen and Behcet's syndrome was diagnosed. Following investigation and monitoring, we identified that the cause was a progressive obliterative focal arteritis of the middle cerebral artery. Such an entity has not previously been reported, although similar cases are described which explain the pathophysiology of the disorder.

Enthesitis as an initial presentation of vascular Behçet's syndrome: a case-based review.

Enthesitis is a characteristic manifestation of spondyloarthropathy (SpA). Historically, Behçet's syndrome (BS) was classified within SpA. Although they are now classified separately, the association between BS and SpA remains controversial. The concept of MHC-I (major histocompatibility complex class I)-opathy has been proposed based on the overlap in immunopathological mechanisms among diseases associated with human leukocyte antigen (HLA) class I. Enthesitis is a frequent complication in patients with BS who also have acne and arthritis. However, information regarding enthesitis in patients with BS without arthritis (BS-WA) is limited. Herein, we report a case of vascular BS complicated by enthesitis. In this case, heel pain was the dominant symptom at presentation. Laboratory tests revealed chlamydia antibody positivity, leading to a tentative diagnosis of reactive arthritis. Despite treatment, C-reactive protein (CRP) levels remained elevated. Imaging revealed numerous aneurysmal lesions in the large vessels. Based on these findings and other symptoms, patient was diagnosed with vascular BS. He tested positive for HLA-B15 and HLA-B46, which are associated with peripheral SpA. Subsequent remission induction therapy for BS was effective and the patient was discharged without complications. Our case and a literature review suggest that there exists a subgroup of BS-WA with a complication of enthesitis, possibly belonging to the spectrum of MHC-I-opathies. It is important to consider BS as a differential diagnosis in patients presenting with enthesitis and to conduct a precise medical history review regarding the symptoms of BS.

Sexual dysfunction among female patients with rheumatic diseases.

To demonstrate the burden of sexual dysfunction (SD) among females with rheumatic diseases, we conducted a cross-sectional comparative study in patients with systemic sclerosis (SSc), systemic lupus erythematosus (SLE), and Behçet's syndrome (BS) along with suitable healthy controls (HCs). Age-matched female patients with SSc (n = 50), SLE (n = 49), and BS (n = 54), along with 52 female HCs were included in this study between April and October, 2021. Sociodemographic features were recorded, and psychometric tests, i.e., female sexual function index (FSFI), Beck depression inventory (BDI), body cathexis scale, and marital adjustment test (MAT) were performed. Scale scores were compared, and binary logistic regression was used to identify predictors for SD in the whole group. The total FSFI and body cathexis scores among the patient groups were significantly lower than those of the HCs (p < 0.001). Depression was significantly more frequent in the patient groups. MAT scores did not differ significantly between the study groups. Patients with SSc had the worst scores in each psychometric index, including MAT. Decreased body cathexis score [OR 0.974, 95% CI (0.957-0.991), p = 0.003] and low MAT score [OR 0.937, 95% CI (0.896-0.980), p = 0.005], and being diagnosed with SSc [OR 6.6, 95% CI (1.975-22.498), p = 0.002], SLE [OR 2.7, 95% CI (0.998-7.753), p = 0.050], and BS [OR 2.8, 95% CI (1.100-7.359), p = 0.031], were identified as independent predictors for SD. Body cathexis seems to be the most important independent predictor for SD, and the burden of SD appears heavier in patients with SSc, probably due to poor body image satisfaction.

The Association of Behçet's Disease on the Quality of Life for Children and Their Parents.

Background and Aim Chronic diseases profoundly impact people's quality of life (QoL). Behçet's Disease (BD) is a multisystemic chronic disease characterized by vasculitis of various vessels. We aimed to assess QoL in pediatric BD patients and their parents. Methods We included pediatric BD patients meeting the pediatric BD classification criteria in a cross-sectional study conducted from June to December 2022. We recorded patients' clinical characteristics and assessed their QoL using PedsQL. Parents' QoL was evaluated using WHOQOL-Bref. Results The study involved 38 patients (60.5% girls, 39.5% boys) with a median age of 15.5 years (10-17) and a disease duration of 2 years (1-4) and their 38 parents. All patients exhibited oral aphthae, and many had other mucocutaneous findings: genital ulcers (78.9%), pseudofolliculitis (76.3%), and erythema nodosum (23.6%). Some patients had uveitis (13.1%), vascular (13.1%), neurological (10.5%), and gastrointestinal (5.2%) involvement. All patients were in remission under treatment during the study. Median PedsQL scores for total, physical health, and psychosocial health were 74.5(40-94.8), 76.5(43-100), and 75(25-92), respectively, with 14 patients scoring below the cut-off value. Girls had lower physical health scores than boys (p=0.004), and a negative correlation emerged between disease duration and PedsQL score (r=0.648, p=0.001). The median WHOQOL score among parents was 50(25-100), with 20 scoring below the cut-off value. Conclusion The QoL was low for one-third of children with pediatric BD and more than half of their parents.Similar to numerous chronic illnesses, factors such as the duration of the disease and gender were associated with the QoL in pediatric BD.

Screening for familial disease presence in first-degree relatives of Behçet's disease patients: Is measurement of common femoral vein wall thickness valuable for the diagnosis?

OBJECTIVES: We aimed to assess first degree relatives (FDRs) of BD patients for the presence of clinical symptoms and signs of BD and evaluate common femoral vein (CFV) wall thickness measurement for the diagnosis. METHODS: Patients with BD(n=129) and FDRs(n=230) of these patients were included. FDRs were questioned in terms of BD symptoms by phone. Pathergy test and CFV wall thickness measurement were performed among 111 FDRs who accepted the clinical assessment. Clinical assessment group were classified according to the criteria sets for BD. FDRs who did not meet the criteria sets and had at least one clinical finding in addition to oral aphthae(OA) were categorized as the "suspected BD". RESULTS: :We observed increased frequency of isolated BD manifestations in FDRs. Ten FDRs were diagnosed with BD during clinical evaluation. Significantly increased CFV wall thickness was observed in FDRs of BD patients fulfilling diagnostic BD criteria (p<0.001 for both sides) and also in those with suspected BD group (p<0.05 for both sides). Presence of OA, genital ulcer, folliculitis or erythema nodosum were associated with increased CFV wall thickness (p<0.05). CONCLUSION: . Our results suggest that CFV wall thickness measurement can be used in diagnosis of familial BD.

Impact of celiac disease in Behçet's syndrome patients: a study based on the database of Türkiye.

Background/aim: Our primary aim was to investigate the effects of concomitant celiac disease (CD) on the clinical characteristics of Behçet's syndrome (BS) patients. Materials and method: The study was a retrospective, nationwide, multicenter study. Turkish Ministry of Health National Electronic Database (e-Nabiz) is used under Health Ministry's supervision to extract the subject's data. Statistical analysis: Statistical analyses were made by the Statistical Package for Social Sciences (SPSS) software version 20 (IBM Corp., Armonk, New York). Continuous variables were presented by mean ± standard derivation (SD) or median (min-max) according to normality and compared by student-t test. A binary logistic regression analysis was performed to further investigating the relation between having a concomitant CD with each BD manifestation and comorbidity, frequencies of which were detected to be significantly different in the student-test. Results: A total of 84,241 patients diagnosed with BS were analyzed, and CD was identified in 175 (0.21 %) patients. The group with CD had a mean age of 41.30 ± 13.69 which was significantly younger. the prevalence of females was significantly higher (71.4%). The mean age of first admission for BS was also significantly younger in the group with CD (36.64 ± 13.28). BS patients with CD had a significantly higher prevalence of inflammatory bowel disease (27.2% vs. 7.3%, p < 0.001). When comorbid conditions were investigated depression (35.4% vs. 23.3%, p < 0.001), migraine (7.4 % vs. 2.6%, p < 0.001), fibromyalgia (10.9% vs. 4.5%, p < 0.001) and osteoporosis (12.6% vs. 6.6%, p = 0.001) were significantly more frequent in BS patients with CD. Conclusion: Our results suggest coexistence of CD in BS patients is related to female dominance and probably to an earlier disease onset. Several CD-related comorbidities as well as inflammatory bowel disease were more frequent in the CD group which implied an increased overall disease burden.

Outcome measures in Behçet syndrome.

Disease assessment has been challenging in Behçet syndrome due to the heterogeneous disease course and multiorgan involvement with variable treatment response. There have been several recent improvements regarding outcome measures including development of a Core Set of Domains for Behçet syndrome and novel instruments for assessing specific organs and overall damage. This review focuses on the current state of outcome measures in Behçet syndrome, unmet needs, and a research agenda towards the development of standardized and validated outcome measure instruments.

Microbiome in Behcet's syndrome.

This review will discuss the current understanding of the role of microbiomes in Behcet's Syndrome, their influence on immune response and disease and potential future studies.

Difficult-to-treat Behçet syndrome: A therapeutic approach.

Behcet syndrome is a systemic vasculitis which can involve many different organ systems. As such, treatment decisions need to be based on organ system involved. In addition, specific patient characteristics potentially predict milder or more severe course, and all these factors need to be taken into consideration when making treatment decisions. In this paper, we review the current approaches to treating Behcet syndrome patients.

Infliximab for vascular involvement in Behçet's syndrome.

OBJECTIVE: Vascular involvement is an important cause of morbidity and mortality in patients with Behçet's syndrome (BS). We aimed to survey the efficacy and safety of infliximab (IFX) in BS patients with vascular involvement followed in a dedicated tertiary center. METHODS: Charts of all BS patients who used IFX for vascular involvement between 2004 and 2022 were reviewed. Primary endpoint was remission at Month 6, defined as lack of new clinical symptoms and findings associated with vascular lesion, lack of worsening of the primary vascular lesion and a new vascular lesion on imaging, and CRP < 10 mg/L. Relapse was defined as development of a new vascular lesion or recurrence of the preexisting vascular lesion. RESULTS: Among the 127 patients (102 men, mean age at IFX initiation: 35.8 ± 9.0 years) treated with IFX, 110 (87%) had received IFX for remission induction and 87 of these (79%) were already on immunosuppressives when the vascular lesion requiring IFX developed. The remission rate was 73% (93/127) at Month 6 and 63% (80/127) at Month 12. Seventeen patients experienced relapses. Remission rates were better among patients with pulmonary artery involvement and venous thrombosis compared to patients with non-pulmonary artery involvement and venous ulcers. Fourteen patients had adverse events leading to IFX discontinuation and 4 had died due to lung adenocarcinoma, sepsis, and pulmonary hypertension-related right heart failure due to pulmonary artery thrombosis (n = 2). CONCLUSION: Infliximab seems to be effective in majority of BS patients with vascular involvement, even in those who are refractory to immunosuppressives and glucocorticoids.

EULAR study group on 'MHC-I-opathy': identifying disease-overarching mechanisms across disciplines and borders.

The 'MHC-I (major histocompatibility complex class I)-opathy' concept describes a family of inflammatory conditions with overlapping clinical manifestations and a strong genetic link to the MHC-I antigen presentation pathway. Classical MHC-I-opathies such as spondyloarthritis, Behçet's disease, psoriasis and birdshot uveitis are widely recognised for their strong association with certain MHC-I alleles and gene variants of the antigen processing aminopeptidases ERAP1 and ERAP2 that implicates altered MHC-I peptide presentation to CD8+T cells in the pathogenesis. Progress in understanding the cause and treatment of these disorders is hampered by patient phenotypic heterogeneity and lack of systematic investigation of the MHC-I pathway.Here, we discuss new insights into the biology of MHC-I-opathies that strongly advocate for disease-overarching and integrated molecular and clinical investigation to decipher underlying disease mechanisms. Because this requires transformative multidisciplinary collaboration, we introduce the EULAR study group on MHC-I-opathies to unite clinical expertise in rheumatology, dermatology and ophthalmology, with fundamental and translational researchers from multiple disciplines such as immunology, genomics and proteomics, alongside patient partners. We prioritise standardisation of disease phenotypes and scientific nomenclature and propose interdisciplinary genetic and translational studies to exploit emerging therapeutic strategies to understand MHC-I-mediated disease mechanisms. These collaborative efforts are required to address outstanding questions in the etiopathogenesis of MHC-I-opathies towards improving patient treatment and prognostication.

Organ damage is a major determinant of work productivity impairment in Behçet's Syndrome: a post-hoc analysis of the BODI validation study.

OBJECTIVES: To evaluate the prevalence, magnitude, and potential determinants of work productivity impairment in patients with Behçet's Syndrome (BS), focusing on the role of irreversible organ damage. METHODS: A post-hoc analysis of the BS overall damage index (BODI) prospective validation study was performed. Demographics and clinical features were recorded in all patients. The Work Productivity and Activity Impairment: General Health (WPAI: GH) questionnaire was administered to assess the work limitation and the BODI to measure organ damage. The independent effect of BS features on WPAI: GH outcomes was evaluated by regression analysis. RESULTS: Out of 148 patients, 34.5% were unemployed, with age (OR 1.035) and BODI score (OR 1.313 for 1-unit increase) as the only factors significantly (p< 0.05) associated with the unemployment state. An overall work impairment was reported in about 64.2% of the employed patients. Indeed, 22.7% reported missing work h due to their health (absenteeism), with a mean time loss of 34.4%; whereas 60.2% declared a reduced performance at work because of their health (presenteeism), with a mean productivity impairment of 45.4%. Ocular damage was associated with absenteeism (ß 0.225); female sex (ß 0.260), physician global assessment of disease activity (ß 0.502) and an increased BODI score (ß 0.166 for 1-point increase) with presenteeism; fibromyalgia (ß 0.246), physician global assessment (ß 0.469), and musculoskeletal damage (ß 0.325) with overall work impairment. CONCLUSIONS: Disease activity and organ damage accrual remarkably affect work productivity in BS patients. Achieving remission and preventing damage accrual are crucial and complementary objectives.

Validation of the PEDiatric Behçet's Disease classification criteria: an evidence-based approach.

OBJECTIVES: to validate the PEDiatric Behçet's Disease classification criteria (PEDBD) with an evidence-based approach. METHODS: 210 pediatric patients (70 Behçet's disease (BD), 40 Periodic Fever, Aphthous stomatitis, Pharyngitis, Adenitis, 35 familial Mediterranean fever, 26 hyper-IgD syndrome, 22 TNF-Receptor associated Periodic fever Syndrome, 17 undefined recurrent fevers) were randomly selected from the Eurofever Registry. A set of 11 experienced clinicians/researchers blinded to the original diagnosis evaluated the patients. Using the table consensus as gold standard (agreement ≥ 80%), the PEDBD, ISG and ICBD criteria were applied to BD patients and to confounding diseases with other autoinflammatory conditions in order to define their sensitivity, specificity and accuracy. RESULTS: At the end of the third round, a consensus was reached in 139/210 patients (66.2%). The patients with a consensus ≥80% were classified as confirmed-BD (n = 24), and those with an agreement of 60-79% as probable-BD (n = 10). When comparing these patients with the confounding diseases group, an older age at disease onset, the presence of oral and genital ulcers, skin papulo-pustular lesions, a positive pathergy test and posterior uveitis were BD distinctive elements. The ISG, ICBD and PEDBD criteria were applied to confirmed-BD and to the confounding disease group, showing a sensitivity of 0.50, 0.79 and 0.58, a specificity of 1.00, 0.97, 0.99, and an accuracy of 0.91, 0.94 and 0.92, respectively. CONCLUSIONS: the PEDBD criteria were very specific, while the ICBD resulted to be more sensitive. The complexity of childhood BD suggests larger prospective international cohorts to further evaluate the performance of the criteria.