The gut-enthesis axis and the pathogenesis of Spondyloarthritis.

Subclinical inflammation is associated with Spondylarthritis (SpA). SpA patients show features of dysbiosis, altered gut barrier function, and local expansion of innate and innate-like cells involved in type 3 immune response. The recirculation of intestinal primed immune cells into the bloodstream and, in some cases, in the joints and the inflamed bone marrow of SpA patients gave the basis of the gut-joint axis theory. In the light of the critical role of enthesis in the pathogenesis of SpA and the identification of mucosal-derived immune cells residing into the normal human enthesis, a gut-enthesis axis is also likely to exist. This work reviews the current knowledge on enthesis-associated innate immune cells' primary involvement in enthesitis development, questions their origin, and critically discusses the clues supporting the existence of a gut-enthesis axis contributing to SpA development.

Expression of HIF1α in intestinal epithelium restricts arthritis inflammation by inhibiting RIPK3-induced cell death machinery.

OBJECTIVES: To investigate the mechanism by which intestinal epithelial cell (IEC) death induces arthritis. METHODS: IEC death was assessed by staining for necroptosis and apoptosis markers and fluorescence in situ hybridisation at different time points during collagen-induced arthritis (CIA). During the development of CIA, messenger RNA (mRNA) sequencing was performed, followed by Gene Ontology enrichment analysis of differentially expressed genes. Mice deficient for hypoxia-inducible factor 1α (Hif1a) in IECs (Hif1a ∆IEC) were generated and induced for arthritis. mRNA sequencing, chromatin immunoprecipitated (ChIP) DNA sequencing and ChIP-qualitative PCR were performed on IECs from Hif1a ∆IEC mice and littermate controls. Effects of HIF1α stabilisation by inhibition of prolyl hydroxylase domain-containing enzymes and treatment with the inhibitor of receptor-interacting protein kinase-3 (RIPK3) were tested in intestinal organoids and in CIA. RESULTS: IEC underwent apoptotic and necroptotic cell death at the onset of arthritis, leading to impaired gut barrier function. HIF1α was identified as one of the most upregulated genes in IECs during the onset of arthritis. Deletion of Hif1a in IEC enhanced IEC necroptosis, triggered intestinal inflammation and exacerbated arthritis. HIF1α was found to be a key transcriptional repressor for the necroptosis-inducing factor RIPK3. Enhanced RIPK3 expression, indicating necroptosis, was also found in the intestinal epithelium of patients with new-onset rheumatoid arthritis. Therapeutic stabilisation of HIF1α as well as small-molecule-based RIPK3 inhibition rescued intestinal necroptosis in vitro and in vivo and suppressed the development of arthritis. CONCLUSION: Our results identify IEC necroptosis as a critical link between the gut and the development of arthritis.

CD8+ tissue-resident memory T cells are expanded in primary Sjögren's disease and can be therapeutically targeted by CD103 blockade.

OBJECTIVE: Tissue-resident memory cells (Trm) are a subset of T cells residing persistently and long-term within specific tissues that contribute to persistent inflammation and tissue damage. We characterised the phenotype and function of Trm and the role of CD103 in primary Sjogren's syndrome (pSS). METHODS: In both pSS and non-pSS sicca syndrome patients, we examined Trm frequency, cytokine production in salivary glands (SG) and peripheral blood (PB). We also analysed Trm-related gene expression in SG biopsies through bulk and single-cell RNA sequencing (scRNAseq). Additionally, we investigated Trm properties in an immunisation-induced animal model of pSS (experimental SS, ESS) mouse model and assessed the effects of Trm inhibition via intraglandular anti-CD103 monoclonal antibody administration. RESULTS: Transcriptomic pSS SG showed an upregulation of genes associated with tissue recruitment and long-term survival of Trm cells, confirmed by a higher frequency of CD8+CD103+CD69+ cells in pSS SG, compared with non-specific sialadenitis (nSS). In SG, CD8+ CD103+ Trm contributed to the secretion of granzyme-B and interferon-γ, CD8+ Trm cells were localised within inflammatory infiltrates, where PD1+CD8+ T cells were also increased compared with nSS and MALT lymphoma. scRNAseq of PB and pSS SG T cells confirmed expression of CD69, ITGAE, GZMB, GZMK and HLA-DRB1 among CD3+CD8+ SG T cells. In the SG of ESS, CD8+CD69+CD103+ Trm producing Granzyme B progressively expanded. However, intraglandular blockade of CD103 in ESS reduced Trm, reduced glandular damage and improved salivary flow. CONCLUSIONS: CD103+CD8+Trm cells are expanded in the SG of pSS and ESS, participate in tissue inflammation and can be therapeutically targeted.

EULAR recommendations for the management of psoriatic arthritis with pharmacological therapies: 2023 update.

OBJECTIVE: New modes of action and more data on the efficacy and safety of existing drugs in psoriatic arthritis (PsA) required an update of the EULAR 2019 recommendations for the pharmacological treatment of PsA. METHODS: Following EULAR standardised operating procedures, the process included a systematic literature review and a consensus meeting of 36 international experts in April 2023. Levels of evidence and grades of recommendations were determined. RESULTS: The updated recommendations comprise 7 overarching principles and 11 recommendations, and provide a treatment strategy for pharmacological therapies. Non-steroidal anti-inflammatory drugs should be used in monotherapy only for mild PsA and in the short term; oral glucocorticoids are not recommended. In patients with peripheral arthritis, rapid initiation of conventional synthetic disease-modifying antirheumatic drugs is recommended and methotrexate preferred. If the treatment target is not achieved with this strategy, a biological disease-modifying antirheumatic drug (bDMARD) should be initiated, without preference among modes of action. Relevant skin psoriasis should orient towards bDMARDs targeting interleukin (IL)-23p40, IL-23p19, IL-17A and IL-17A/F inhibitors. In case of predominant axial or entheseal disease, an algorithm is also proposed. Use of Janus kinase inhibitors is proposed primarily after bDMARD failure, taking relevant risk factors into account, or in case bDMARDs are not an appropriate choice. Inflammatory bowel disease and uveitis, if present, should influence drug choices, with monoclonal tumour necrosis factor inhibitors proposed. Drug switches and tapering in sustained remission are also addressed. CONCLUSION: These updated recommendations integrate all currently available drugs in a practical and progressive approach, which will be helpful in the pharmacological management of PsA.

Short-term effectiveness of guselkumab in psoriatic arthritis patients and suggestive features of axial involvement: results from a real-life multicentre cohort.

OBJECTIVE: To evaluate the short-term effectiveness of guselkumab in patients with psoriatic arthritis (PsA) and suggestive features of axial involvement in a prospective "real-life" multicentre cohort. METHODS: Between June 2022 and June 2023, PsA patients with axial involvement were evaluated if treated at least for 4 months with guselkumab. The effectiveness was evaluated by BASDAI, ASDAS, DAPSA, and achievement of BASDAI ≤ 4, also exploiting predictive factors. In a group of patients, MRI findings on sacroiliac joints were assessed before and after guselkumab administration. RESULTS: Sixty-seven patients with PsA and suggestive features of axial involvement (age 53.4 ± 11.2 years, male sex 26.9%) were treated with guselkumab. After 4 months, a significant reduction of BASDAI, ASDAS, and DAPSA was observed. A ΔBASDAI of -2.11 ± 0.43 was estimated assessing the mean difference values before and after guselkumab administration and 52.2% of patients reached a BASDAI ≤ 4. In 27 patients, MRI findings on sacroiliac joints were assessed before and after guselkumab administration. A reduction of 0.80 or larger of the sacroiliac joint lesion score was observed in the majority of patients (70.3%) based on MRI improvements, paralleling with the clinical response.No life-threatening side effects were recorded; 17.9% of patients reported minor adverse events mainly injection site reactions. CONCLUSIONS: The short-term effectiveness of guselkumab in patients with PsA and suggestive features of axial involvement was shown. Although further studies are needed, our multicentre "real-life" study may suggest the clinical usability of guselkumab in this context.

The assessment of the drug retention rate of secukinumab in patients with psoriatic arthritis in a real-life multicentre cohort.

OBJECTIVES: We aimed to evaluate the drug retention rate (DRR) of secukinumab, an anti-IL-17A monoclonal antibody, in patients with psoriatic arthritis (PsA) in a real-life cohort, and to assess the impact of comorbidities and patient clinical characteristics on the DRR of secukinumab. METHODS: A retrospective study of prospective followed-up patients was performed to evaluate the DRR of secukinumab on patients with PsA attending the recruiting centres between January 2016 and June 2022. RESULTS: In 207 patients with PsA, a 60-month DRR of secukinumab of 57.0% was estimated (mean time of administration of 21.5±17.1 months). Male gender, age ≥65 years, disease duration ≥5 years and ≥10 years did not influence the DRR of secukinumab. The presence of comorbidities, considering any concomitant disorder, did not affect the DRR of secukinumab. In patients with cardiometabolic multimorbidity, a trend toward a better DRR of secukinumab was recorded. In fact, patients with high blood pressure, dyslipidaemia, and type 2 diabetes showed a trend toward an improved DRR of secukinumab. Furthermore, the presence of obesity did not influence the DRR of secukinumab. Different dosages, previous bDMARDs, and concomitant therapy with csDMARDs did not influence the DRR of secukinumab. CONCLUSIONS: A cumulative 60-month DRR of secukinumab of 57.0% in patients with PsA was retrieved. The presence of cardiometabolic multimorbidity could be associated with an improved DRR of secukinumab, whereas obesity did not affect this feature in our cohort. Previous bDMARDs, concomitant csDMARDs, and different drug dosages could not influence the DRR of secukinumab over time.

Prostaglandin E2/EP4 axis is upregulated in Spondyloarthritis and contributes to radiographic progression.

Ankylosing spondylitis (AS) is an inflammatory disease leading to spine ankylosis; however, the mechanisms behind new bone formation are still not fully understood. Single Nucleotide Polymorphisms (SNPs) in PTGER4, encoding for the receptor EP4 of prostaglandin E2 (PGE2), are associated with AS. Since the PGE2-EP4 axis participates in inflammation and bone metabolism, this work aims at investigating the influence of the prostaglandin-E2 axis on radiographic progression in AS. In 185 AS (97 progressors), baseline serum PGE2 predicted progression, and PTGER4 SNP rs6896969 was more frequent in progressors. Increased EP4/PTGER4 expression was observed in AS circulating immune cells, synovial tissue, and bone marrow. CD14highEP4 + cells frequency correlated with disease activity, and when monocytes were cocultured with mesenchymal stem cells, the PGE2/EP4 axis induced bone formation. In conclusion, the Prostaglandin E2 axis is involved in bone remodelling and may contribute to the radiographic progression in AS due to genetic and environmental upregulation.

Butyrophilin 2a2 (Btn2a2) expression on thymic epithelial cells promotes central T cell tolerance and prevents autoimmune disease.

Butyrophilins are surface receptors belonging to the immunoglobulin superfamily. While several members of the butyrophilin family have been implicated in the development of unconventional T cells, butyrophilin 2a2 (Btn2a2) has been shown to inhibit conventional T cell activation. Here, we demonstrate that in steady state, the primary source of Btn2a2 are thymic epithelial cells (TEC). Absence of Btn2a2 alters thymic T cell maturation and bypasses central tolerance mechanisms. Furthermore, Btn2a2-/- mice develop spontaneous autoimmunity resembling human primary Sjögren's Syndrome (pSS), including formation of tertiary lymphoid structures (TLS) in target organs. Ligation of Btn2a2 on developing thymocytes is associated with reduced TCR signaling and CD5 levels, while absence of Btn2a2 results in increased TCR signaling and CD5 levels. These results define a novel role for Btn2a2 in promoting central tolerance by modulating TCR signaling strength and indicate a potential mechanism of pSS development.

UBE2L3 regulates TLR7-induced B cell autoreactivity in Systemic Lupus Erythematosus.

Both TLR7 and NF-κB hyperactivity are known to contribute to pathogenesis in Systemic Lupus Erythematosus (SLE), driving a pro-interferon response, autoreactive B cell expansion and autoantibody production. UBE2L3 is an SLE susceptibility gene which drives plasmablast/plasma cell expansion in SLE, but its role in TLR7 signalling has not been elucidated. We aimed to investigate the role of UBE2L3 in TLR7-mediated NF-κB activation, and the effect of UBE2L3 inhibition by Dimethyl Fumarate (DMF) on SLE B cell differentiation in vitro. Our data demonstrate that UBE2L3 is critical for activation of NF-κB downstream of TLR7 stimulation, via interaction with LUBAC. DMF, which directly inhibits UBE2L3, significantly inhibited TLR7-induced NF-κB activation, differentiation of memory B cells and plasmablasts, and autoantibody secretion in SLE. DMF also downregulated interferon signature genes and plasma cell transcriptional programmes. These results demonstrate that UBE2L3 inhibition could potentially be used as a therapy in SLE through repurposing of DMF, thus preventing TLR7-driven autoreactive B cell maturation.

Seronegative rheumatoid arthritis: one year in review 2023.

In the past 20 years, earlier diagnosis and more intensive management have considerably improved the prognosis of rheumatoid arthritis (RA), with milder disease course achieved in particular in seropositive patients. In contrast, seronegative RA has remained largely neglected, and continues to be surrounded by uncertainties regarding its correct diagnosis, clinical phenotype, optimal treatment strategies and relevant outcomes.The purpose of this review is to summarise new insights about the pathogenic, clinical and prognostic peculiarities of seronegative RA that emerged during 2022, and that make this disease subset at least partially different from its seropositive counterpart.

Real-life efficacy of guselkumab in patients with early psoriatic arthritis.

OBJECTIVES: To assess the efficacy of the novel anti-IL-23 monoclonal antibody guselkumab in a real-life observational cohort of patients with early PsA. METHODS: We conducted an observational study on patients with early PsA followed by the joint dermatology-rheumatology clinics of two Italian centres starting therapy with guselkumab for severe skin involvement. Each patient was evaluated at baseline and every 24 weeks for one year, recording Disease Activity Index for PsA (DAPSA), PASI, VAS Pain, VAS Prutitus, Patient's Global Assessment (PtGA) and assessing DAPSA response. RESULTS: Twenty-four patients were recruited (16 women). The mean duration of skin disease was 12.5 years (CI 8; 17), but all patients had a shorter articular disease duration, 21.29 months (CI 15.9; 26.68). At baseline, all patients displayed a moderate cutaneous disease with a mean PASI of 15.2 (CI 11.7-18.6) and high disease activity, characterized by mean DAPSA of 26.84 (CI 22.49-31.19). An inflammatory low back pain was reported by five patients (20%) with a mean BASDAI 5.1 (CI 4,38-5,85) at baseline. The majority of guselkumab-treated patients (n = 18; 75%) reached DAPSA remission or DAPSA low disease activity after six months. Seventeen out of 24 patients completed 12 months of treatment, 11 of them (65%) in low disease activity, six (35%) in remission. All patients with axial disease reported improvement of inflammatory low back pain at week 24 with a mean BASDAI 2.98 (CI 2,18- 3,77). No significant side effects were reported. CONCLUSIONS: Real-life data on a cohort of early PsA patients confirm the efficacy and safety of guselkumab on peripheral and axial manifestations.

Increased plasma levels of Gas6 and its soluble tyrosine kinase receptors Mer and Axl are associated with immunological activity and severity of lupus nephritis.

OBJECTIVES: Growth arrest-specific 6 (Gas6) and its receptors have been shown to play a crucial role in the homeostasis of the innate immune system by regulating apoptosis and inflammation. We aimed to verify whether an impairment of this system is associated with systemic lupus erythematosus (SLE) disease activity and with lupus nephritis (LN). METHODS: Plasma Gas6 and the soluble cleaved form of the receptors MerTK (sMer) and Axl (sAxl) concentrations were measured in n=59 SLE patients (n=44 with nephritis, 75%) and analysed in relationship to clinical and laboratory data. RESULTS: Patients with LN were characterised by higher Gas6 (19.0 ng/mL [16.8-24.5] vs. 16.5 ng/mL [13.89-18.91]; p=0.03) and sAxl plasma levels than those without LN (31.36 ng/mL [25.1-41.4] vs. 20.2 ng/mL [15.6-30.7]; p=0.03); conversely sMer plasma concentrations were similar between groups. All the three biomarkers studied were directly correlated to creatinine and daily proteinuria, being inversely related to creatinine clearance. 39 patients had a proteinuria level of <0.5 mg/day, 14 between 0.5 and 3.5 mg/day and 5 had ≥3.5 g/day; Gas6, sAxl and sMer plasma concentrations significantly increased for increasing degree of proteinuria (test for trend p=0.0002; p=0.02; p=0.009, respectively).These correlations were confirmed in multiple linear regression analysis models accounting for gender, age, disease duration and concomitant treatment. CONCLUSIONS: Plasma Gas6, sAxl and sMer concentrations are associated with the severity of LN in patients affected by SLE. The excess cleavage of TAM receptors might contribute to LN pathogenesis.

De novo mutations implicate novel genes in systemic lupus erythematosus.

The omnigenic model of complex disease stipulates that the majority of the heritability will be explained by the effects of common variation on genes in the periphery of core disease pathways. Rare variant associations, expected to explain far less of the heritability, may be enriched in core disease genes and thus will be instrumental in the understanding of complex disease pathogenesis and their potential therapeutic targets. Here, using complementary whole-exome sequencing, high-density imputation, and in vitro cellular assays, we identify candidate core genes in the pathogenesis of systemic lupus erythematosus (SLE). Using extreme-phenotype sampling, we sequenced the exomes of 30 SLE parent-affected-offspring trios and identified 14 genes with missense de novo mutations (DNM), none of which are within the >80 SLE susceptibility loci implicated through genome-wide association studies. In a follow-up cohort of 10, 995 individuals of matched European ancestry, we imputed genotype data to the density of the combined UK10K-1000 genomes Phase III reference panel across the 14 candidate genes. Gene-level analyses indicate three functional candidates: DNMT3A, PRKCD, and C1QTNF4. We identify a burden of rare variants across PRKCD associated with SLE risk (P = 0.0028), and across DNMT3A associated with two severe disease prognosis sub-phenotypes (P = 0.0005 and P = 0.0033). We further characterise the TNF-dependent functions of the third candidate gene C1QTNF4 on NF-κB activation and apoptosis, which are inhibited by the p.His198Gln DNM. Our results identify three novel genes in SLE susceptibility and support extreme-phenotype sampling and DNM gene discovery to aid the search for core disease genes implicated through rare variation.

Pathogenesis of primary Sjögren's syndrome beyond B lymphocytes.

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder affecting exocrine glands of the body, prevalently lacrimal and salivary glands. The pSS pathogenesis has been thought to be B-cell-centric and several clinical trials have been carried out in order to clarify the therapeutic role of B-cell depletion in patients with pSS. Unfortunately, however, B-cell depletion with rituximab has failed in demonstrating any significant results in pSS patients. Besides the contribution of B cells in the pathogenesis of pSS, effector Tfh, Th17 and Th22 cells, follicular dendritic cells (DCs), innate cells (ICs) and several cytokines, chemokines and miRNA have been proved to participate to the development of this systemic disease. Understanding these molecular processes may help guide research into resistant diseases and highly targeted therapeutic strategies. This review aims to discuss important pathogenetic mechanisms involved in the initiation and perpetuation of pSS behind the established role of B cells.

Synovial tissue signatures enhance clinical classification and prognostic/treatment response algorithms in early inflammatory arthritis and predict requirement for subsequent biological therapy: results from the pathobiology of early arthritis cohort (PEAC).

OBJECTIVE: To establish whether synovial pathobiology improves current clinical classification and prognostic algorithms in early inflammatory arthritis and identify predictors of subsequent biological therapy requirement. METHODS: 200 treatment-naïve patients with early arthritis were classified as fulfilling RA1987 American College of Rheumatology (ACR) criteria (RA1987) or as undifferentiated arthritis (UA) and patients with UA further classified into those fulfilling RA2010 ACR/European League Against Rheumatism (EULAR) criteria. Treatment requirements at 12 months (Conventional Synthetic Disease Modifying Antirheumatic Drugs (csDMARDs) vs biologics vs no-csDMARDs treatment) were determined. Synovial tissue was retrieved by minimally invasive, ultrasound-guided biopsy and underwent processing for immunohistochemical (IHC) and molecular characterisation. Samples were analysed for macrophage, plasma-cell and B-cells and T-cells markers, pathotype classification (lympho-myeloid, diffuse-myeloid or pauci-immune) by IHC and gene expression profiling by Nanostring. RESULTS: 128/200 patients were classified as RA1987, 25 as RA2010 and 47 as UA. Patients classified as RA1987 criteria had significantly higher levels of disease activity, histological synovitis, degree of immune cell infiltration and differential upregulation of genes involved in B and T cell activation/function compared with RA2010 or UA, which shared similar clinical and pathobiological features. At 12-month follow-up, a significantly higher proportion of patients classified as lympho-myeloid pathotype required biological therapy. Performance of a clinical prediction model for biological therapy requirement was improved by the integration of synovial pathobiological markers from 78.8% to 89%-90%. CONCLUSION: The capacity to refine early clinical classification criteria through synovial pathobiological markers offers the potential to predict disease outcome and stratify therapeutic intervention to patients most in need.

ILC3 in Axial Spondyloarthritis: the Gut Angle.

PURPOSE OF REVIEW: A growing body of evidence supports the relevance of the interleukin-23/interleukin-17 (IL-23/IL-17) pathway for the pathogenesis of axial spondyloarthritis (axSpA) and its treatment. Recently, innate lymphoid cells (ILC), a heterogeneous family of immune effector cells, have been identified as a relevant contributor in tissue homeostasis, partially via IL-23/IL-17 axis. This review describes the biology and the origins of the group 3 ILCs (ILC3s) in humans, focusing on their role in the pathogenesis of axSpA. RECENT FINDINGS: Clinical trials showed the effectiveness of IL23/IL-17 axis inhibition in both spondyloarthritis (SpA) and Inflammatory Bowel Disease (IBD). Recent findings confirm the high prevalence of subclinical gut inflammation in patients with SpA. Translational data in humans have demonstrated an increase in the number of ILC3s responsive to IL-23 and producing either IL-22 or IL-17 in the gut of SpA patients. The observation of gut-derived ILC3s in circulation and at inflamed tissues in patients with SpA suggest a recirculation of ILCs from mucosal site to lymphoid tissues and possibly enthesis and joints. Multiple observations demonstrate the expansion of IL-17- and IL-22-producing ILC3 in the subclinically inflamed gut of SpA patients. These innate immune cells, also observed in normal entheses, seem to be able to re-circulate from the gut to inflamed tissues of SpA patients, thus contributing to the disease perpetuation. The development of tools that can provide access to diseased tissue from sacroiliac joint and spinal entheses will provide valuable knowledge on the role of ILC3 in axSpA pathogenesis.

Mast cells in early rheumatoid arthritis associate with disease severity and support B cell autoantibody production.

OBJECTIVES: Mast cells (MCs) are involved in the pathogenesis of rheumatoid arthritis (RA). However, their contribution remains controversial. To establish their role in RA, we analysed their presence in the synovium of treatment-naïve patients with early RA and their association and functional relationship with histological features of synovitis. METHODS: Synovial tissue was obtained by ultrasound-guided biopsy from treatment-naïve patients with early RA (n=99). Immune cells (CD3/CD20/CD138/CD68) and their relationship with CD117+MCs in synovial tissue were analysed by immunohistochemistry (IHC) and immunofluorescence (IF). The functional involvement of MCs in ectopic lymphoid structures (ELS) was investigated in vitro, by coculturing MCs with naïve B cells and anticitrullinated protein antibodies (ACPA)-producing B cell clones, and in vivo in interleukin-27 receptor alpha (IL27ra)-deficient and control mice during antigen-induced arthritis (AIA). RESULTS: High synovial MC counts are associated with local and systemic inflammation, autoantibody positivity and high disease activity. IHC/IF showed that MCs reside at the outer border of lymphoid aggregates. Furthermore, human MCs promote the activation and differentiation of naïve B cells and induce the production of ACPA, mainly via contact-dependent interactions. In AIA, synovial MC numbers increase in IL27ra deficient mice, in association with ELS and worse disease activity. CONCLUSIONS: Synovial MCs identify early RA patients with a severe clinical form of synovitis characterised by the presence of ELS.

Complement C3 and fatty liver disease in Rheumatoid arthritis patients: a cross-sectional study.

BACKGROUND: Recent evidence suggested a potential role of complement fraction C3 as a biomarker of nonalcoholic fatty liver disease (NAFLD) in the general population. Aim of this study was to evaluate the performance of C3 for prediction of NAFLD in RA patients. MATERIALS AND METHODS: For the present study, consecutive RA patients were recruited. NAFLD was diagnosed according to predefined ultrasonographic (US) criteria. For comparison, the hepatic steatosis index (HSI) was calculated. RESULTS: Of 164 consecutive RA patients, 41 (25%) were diagnosed with NAFLD. The NAFLD group had a significant lower proportion of females (P = 0·04), higher BMI (P < 0·0001), C-reactive protein (P = 0·04), complement C3 (P = 0·001) and HSI (P = 0·003). In a logistic regression model, only male sex (OR 2·65, 95% CI: 1·08-6·50, P = 0·03), increasing BMI (OR 1·22, 95% CI: 1·02-1·46, P = 0·03) and complement C3 (OR 5·05, 95% CI: 1·06-23·93, P = 0·04) were associated with higher likelihood of being diagnosed with NAFLD. Finally, we built ROC curves for BMI, complement C3 and their combination for prediction of having NAFLD. The best cut-off for BMI was 28·5 kg/m2 and yielded a sensitivity of 66% and a specificity of 71%; the best cut-off for complement C3 was 1·23 g/L and yielded a sensitivity of 76% and a specificity of 64% for classification of NAFLD cases. CONCLUSIONS: Our results provide preliminary evidence for a potential role of complement C3 as a surrogate biomarker of NAFLD in RA patients.