JAK inhibitors in the treatment of adult patients with juvenile idiopathic arthritis: a retrospective monocentric experience.

OBJECTIVES: This study aims to evaluate the efficacy and safety of JAK inhibitors (JAKi) in a monocentric cohort of adult patients with juvenile idiopathic arthritis (JIA). METHODS: Patients attending a rheumatology transition clinic were retrospectively included in case of: i) JIA diagnosis according to current classification criteria (1); ii) age ≥18 years and iii) treatment with JAKi for at least 3 months. RESULTS: Seventeen adult patients with JIA were treated with JAKi (as first JAKi, 9 patients (52.9%) received tofacitinib and 8 (47.1%) baricitinib). At 3 months after JAKi initiation, 8 patients (47%) achieved a response and 4 patients (23.5%) achieved disease remission (3 patients with baricitinib and 1 with tofacitinib, 37.5% vs. 16.7%, p=0.294). None of those with systemic JIA and enthesitis-related arthritis obtained remission; the remission rate at 3 months was higher, although not significantly, in the oligoarticular subset compared to the polyarticular subset (37.5% vs. 20%). Patients with ≤1 active joint involvement at JAKi start had a higher remission rate (50% vs. 22.2%). Subjects who achieved remission on JAKi had a significantly lower pre-treatment DAS28-CRP compared to those with still active disease (p=0.010, Mann-Whitney U=4). A pre-treatment DAS28-CRP <3.76 predicted response to JAKi with 100% sensitivity and 84.6% specificity (p=0.023). The remission rate was lower among patients who had been treated with ≥2 biological drugs before JAKi start (9% vs. 66.7%; p=0.05). One patient in concomitant treatment with leflunomide developed severe arterial hypertension. CONCLUSIONS: JAKi may represent an effective and safe treatment option for adult JIA patients with low/moderate disease activity, particularly in case of oligoarticular involvement.

Deciphering the clinical significance of longitudinal antiphospholipid antibody titers.

In antiphospholipid syndrome (APS), the risk of clinical manifestations increases with higher titers of antiphospholipid antibodies (aPL). Despite the adoption of aPL titers in the classification approach to aPL-positive subjects, the value of longitudinal monitoring of those titers in the follow-up is still debated, being well studied only in systemic lupus erythematosus (SLE). The literature suggests that the rate of aPL positivity decreases during follow-up in primary APS, estimating that seroconversion occurs in between 8.9 and 59% of patients over time. Negativisation of aPL occurs more frequently in asymptomatic aPL carriers than in patients with full-blown APS as well as in subjects with single aPL positivity or low aPL antibody titers. In patients with SLE, aPL typically behave fluctuating from positive to negative and back again in the course of follow-up. The few studies assessing the longitudinal course of aPL positivity with no associated systemic connective tissue disease reported a progressive decrement of aPL titers over time, in particular of antibodies against ß2 glycoprotein I (antiß2GPI) and cardiolipin (aCL) of IgG isotype. After a thrombotic event, aPL titers tend to decrease, as emerged from cohorts of both primary and secondary APS. Hydroxychloroquine has been identified as the most effective pharmacological agent to reduce aPL titers, with multiple studies demonstrating a parallel reduction in thrombosis rate. This review addresses available evidence on the significance of aPL titer fluctuation from clinical, therapeutic and pathogenic perspectives.

16th International congress on antiphospholipid antibodies task force report on antiphospholipid syndrome laboratory diagnostics and trends.

Classification criteria for antiphospholipid syndrome (APS) require IgG or IgM isotypes of the anticardiolipin (aCL) antibodies, anti-ß2 glycoprotein I (anti-ß2GPI) antibodies, and/or the lupus anticoagulant (LA) to satisfy the laboratory disease definition. Over the past 20 years, non-criteria antiphospholipid antibodies (aPL) directed to other proteins of the coagulation cascade (i.e. prothrombin and/or phosphatidylserine-prothrombin complex) or to some domains of ß2GPI have been proposed. This task force concentrated and reviewed the literature on data including aPS/PT, antibodies to domain 4/5 of ß2GPI and the newly described antibodies to protein/HLA-DR complex. In addition, we discussed testing of LA in the 'new' oral anticoagulants' era and the value of triple positivity in the risk assessment of aPL. The conclusions were presented at a special session during the 16th International Congress on aPL, Manchester, UK, September 2019.

Insights into the clinical presentation of juvenile systemic lupus erythematosus: the PRAGMA monocentric cohort of 177 patients.

OBJECTIVES: The aim of this work is to describe the clinical manifestations at onset and during follow-up in a monocentric cohort of patients with juvenile systemic lupus erythematosus (jSLE) from the Paediatric Rheumatology group of the Milan area (PRAGMA). METHODS: Patients were retrospectively included in case of i) SLE diagnosis according to the 1997 American College of Rheumatology or the 2012 SLICC classification criteria and ii) disease onset before 18 years. RESULTS: Among the 177 recruited patients (155 females), haematologic involvement was the most common disease manifestation (75%), followed by joint and cutaneous involvements (70% and 57%, respectively). Renal disease was observed in 58 patients (32.8%), neurological complications in 26 cases (14.7%). Patients presented most commonly 3 clinical manifestations (32.8%), while 2 organ involvements were identified in 54 patients (30.5%) and 4 in 25 subjects (14.1%). The 49 patients with disease onset <10 years had less commonly articular involvement (p=0.02), while patients aged >14.8 years displayed less neurological manifestations (p=0.02). At a median follow-up of 118 month, the disease progressed in 93 patients, with a median of 2 new manifestations per patient. Low complement at diagnosis predicted new clinical manifestations (p=0.013 for C3 and p=0.0004 for C4). The median SLEDAI at diagnosis was 13; SLEDAI was substantially similar at 6 months, decreased at 12 months to remain stable at 18 months and further reduce at 24 months (p<0.0001). CONCLUSIONS: These data from a large jSLE monocentric cohort allow gaining further insights into a rare disease with a still high morbidity burden.

Low complement levels are related to poor obstetric outcomes in women with obstetric antiphospholipid syndrome. The EUROAPS Registry Study Group.

INTRODUCTION: Obstetric antiphospholipid syndrome (OAPS) is an autoimmune disease related to antiphospholipid antibodies (aPL) with primaryinflammatory injury followed by clot cascade activation and thrombus formation. Complement system activation and their participation in aPL-related thrombosis is unclosed. METHODS: We haveanalysed adverse pregnancy outcomes (APO) related to low complement (LC) levels in a cohort of 1048 women fulfilling classification criteria for OAPS. RESULTS: Overall, 223 (21.3%) women presented LC values, during pregnancy. The length of pregnancy was shorter in OAPS women with LC compared to those with normal complement (NC) (median: 33 weeks, interquartile range: [24-38] vs. 35 weeks [27-38]; p = 0.022). Life new-born incidence was higher in patients with NC levels than in those with LC levels (74.4% vs. 67.7%; p = 0.045). Foetal losses were more related to women with triple or double aPL positivity carrying LC than NC values (16.3% vs. 8.0% NC; p = 0.027). Finally, some placental vasculopathies were affected in OAPS patients with LC as late Foetal Growth Restriction (FGR >34 weeks) rise to 7.2% in women with LC vs. 3.2% with NC (p = 0.007). DISCUSSION: Data from our registry indicate that incidence of APO was higher in OAPS women with LC levels and some could be reverted by the correct treatment.

Fluctuation of Anti-Domain 1 and Anti-ß2 -Glycoprotein I Antibody Titers Over Time in Patients With Persistently Positive Antiphospholipid Antibodies.

OBJECTIVE: The present study was undertaken to longitudinally evaluate titers of antibodies against ß2 -glycoprotein I (anti-ß2 GPI) and domain 1 (anti-D1), to identify predictors of variations in anti-ß2 GPI and anti-D1 titers, and to clarify whether antibody titer fluctuations predict thrombosis in a large international cohort of patients who were persistently positive for antiphospholipid antibodies (aPL) in the APS ACTION Registry. METHODS: Patients with available blood samples from at least 4 time points (at baseline [year 1] and at years 2-4 of follow-up) were included. Detection of anti-ß2 GPI and anti-D1 IgG antibodies was performed using chemiluminescence (BIO-FLASH; INOVA Diagnostics). RESULTS: Among 230 patients in the study cohort, anti-D1 and anti-ß2 GPI titers decreased significantly over time (P < 0.0001 and P = 0.010, respectively). After adjustment for age, sex, and number of positive aPL tests, we found that the fluctuations in anti-D1 and anti-ß2 GPI titer levels were associated with treatment with hydroxychloroquine (HCQ) at each time point. Treatment with HCQ, but not immunosuppressive agents, was associated with 1.3-fold and 1.4-fold decreases in anti-D1 and anti-ß2 GPI titers, respectively. Incident vascular events were associated with 1.9-fold and 2.1-fold increases in anti-D1 and anti-ß2 GPI titers, respectively. Anti-D1 and anti-ß2 GPI titers at the time of thrombosis were lower compared to titers at other time points. A 1.6-fold decrease in anti-D1 titers and a 2-fold decrease in anti-ß2 GPI titers conferred odds ratios for incident thrombosis of 6.0 (95% confidence interval [95% CI] 0.62-59.3) and 9.4 (95% CI 1.1-80.2), respectively. CONCLUSION: Treatment with HCQ and incident vascular events in aPL-positive patients predicted significant anti-D1 and anti-ß2 GPI titer fluctuations over time. Both anti-D1 and anti-ß2 GPI titers decreased around the time of thrombosis, with potential clinical relevance.

Immunology of pregnancy and reproductive health in autoimmune rheumatic diseases. Update from the 11th International Conference on Reproduction, Pregnancy and Rheumatic Diseases.

Autoimmune rheumatic diseases (ARD) can affect women and men during fertile age, therefore reproductive health is a priority issue in rheumatology. Many topics need to be considered during preconception counselling: fertility, the impact of disease-related factors on pregnancy outcomes, the influence of pregnancy on disease activity, the compatibility of medications with pregnancy and breastfeeding. Risk stratification and individualized treatment approach elaborated by a multidisciplinary team minimize the risk of adverse pregnancy outcomes (APO). Research has been focused on identifying biomarkers that can be predictive of APO. Specifically, preeclampsia and hypertensive disorders of pregnancy tend to develop more frequently in women with ARD. Placental insufficiency can lead to intrauterine growth restriction and small-for-gestational age newborns. Such APO have been shown to be associated with maternal disease activity in different ARD. Therefore, a key message to be addressed to the woman wishing for a pregnancy and to her family is that treatment with compatible drugs is the best way to ensure maternal and fetal wellbeing. An increasing number of medications have entered the management of ARD, but data about their use in pregnancy and lactation are scarce. More information is needed for most biologic drugs and their biosimilars, and for the so-called small molecules, while there is sufficient evidence to recommend the use of TNF inhibitors if needed for keeping maternal disease under control. Other issues related to the reproductive journey have emerged as "unmet needs", such as sexual dysfunction, contraception, medically assisted reproduction techniques, long-term outcome of children, and they will be addressed in this review paper. Collaborative research has been instrumental to reach current knowledge and the future will bring novel insights thanks to pregnancy registries and prospective studies that have been established in several Countries and to their joint efforts in merging data.

Long-term Outcome of Children Born to Women with Autoimmune Rheumatic Diseases: A Multicentre, Nationwide Study on 299 Randomly Selected Individuals.

The concern about the offspring's health is one of the reasons for a reduced family size of women with rheumatic diseases (RD). Increased risk of autoimmune diseases (AD) and neurodevelopmental disorders (ND) has been reported in children born to patients with RD. Within a nationwide survey about reproductive issues of women with RD, we aimed at exploring the long-term outcome of their children. By surveying 398 patients who received their diagnosis of RD during childbearing age (before the age of 45), information about the offspring were obtained from 230 women who declared to have had children. A total of 148 (64.3%) patients were affected by connective tissue diseases (CTD) and 82 (35.7%) by chronic arthritis. Data on 299 children (156 males, 52.1%; mean age at the time of interview 17.1 ± 9.7 years) were collected. Twelve children (4.0%), who were born to patients with CTD in 75% of the cases, were affected by AD (8 cases of celiac disease). Eleven children had a certified diagnosis of ND (3.6%; 6 cases of learning disabilities); 9 of them were born to mothers with CTD (5 after maternal diagnosis). No association was found between ND and prenatal exposure to either maternal autoantibodies or anti-rheumatic drugs. Absolute numbers of offspring affected by AD and ND were low in a multicentre cohort of Italian women with RD. This information can be helpful for the counselling about reproductive issues, as the health outcomes of the offspring might not be an issue which discourage women with RD from having children.

Anti-phospholipid antibodies and reproductive failures.

Anti-phospholipid syndrome (APS) recapitulates the link between autoimmunity and pregnancy failure: Acquired anti-phospholipid antibodies (aPL) play a pathogenic role in pregnancy complications. The diagnosis of obstetric APS can easily be pursued when women present with laboratory and clinical features fulfilling the international classification criteria. Standard therapeutic approach to obstetric APS consists in the association of anti-platelet agents and anticoagulants. Most patients achieve a live birth thanks to conventional treatment; however, approximately 20% fail to respond and are managed with additional therapeutic tools added on the top of conventional treatment. Surely, a refinement of risk stratification tools would allow early identification of high-risk pregnancies that warrant tailored treatment. In real life, obstetricians and rheumatologists face complex diagnostic scenarios including women with pregnancy morbidities other than those mentioned in classification criteria such as one or two early losses and premature birth after 34 weeks due to preeclampsia or placental insufficiency, women with low-titer aPL not fulfilling criteria laboratory requirements, women with positive non-criteria aPL, asymptomatic aPL carriers, and infertile women found to be aPL-positive. This review focuses on some of the several unanswered questions related to diagnostic, prognostic, and therapeutic aspects in obstetric APS.

EUREKA algorithm predicts obstetric risk and response to treatment in women with different subsets of anti-phospholipid antibodies.

OBJECTIVES: aPL, the serum biomarkers of APS, are the most common acquired causes of pregnancy morbidity (PM). This study investigates the impact of aPL positivity fulfilling classification criteria ('criteria aPL') and at titres lower than thresholds considered by classification criteria ('low-titre aPL') on PM and assesses the effectiveness of low-dose aspirin (LDASA), low molecular weight heparin (LMWH) and HCQ in reducing the probability of PM (PPM). METHODS: Longitudinal data on 847 pregnancies in 155 women with persistent aPL at any titre and 226 women with autoimmune diseases and negative aPL were retrospectively collected. A generalized estimating equations model for repeated measures was applied to quantify PPM under different clinical situations. RESULTS: EUREKA is a novel algorithm that accurately predicts the risk of aPL-associated PM by considering aPL titres and profiles. aPL significantly impact PPM when at low titres and when fulfilling classification criteria. PPM was further stratified upon the aPL tests: aCL IgG/IgM and anti-ß2-glycoprotein I (ß2GPI) IgM, alone or combined, do not affect the basal risks of PPM, an increase occurs in case of positive LA or anti-ß2GPI IgG. LDASA significantly affects PPM exclusively in women with low-titre aPL without anti-ß2GPI IgG. The LDASA + LMWH combination significantly reduces PPM in all women with low-titre aPL and women with criteria aPL, except those carrying LA and anti-ß2GPI IgG. In this group, the addition of HCQ further reduces PPM, although not significantly. CONCLUSION: EUREKA allows a tailored therapeutic approach, impacting everyday clinical management of aPL-positive pregnant women.

Antiphospholipid Antibody Profile Stability Over Time: Prospective Results From the APS ACTION Clinical Database and Repository.

OBJECTIVE: The APS ACTION Registry studies long-term outcomes in persistently antiphospholipid antibody (aPL)-positive patients. Our primary objective was to determine whether clinically meaningful aPL profiles at baseline remain stable over time. Our secondary objectives were to determine (1) whether baseline characteristics differ between patients with stable and unstable aPL profiles, and (2) predictors of unstable aPL profiles over time. METHODS: A clinically meaningful aPL profile was defined as positive lupus anticoagulant (LAC) test and/or anticardiolipin (aCL)/anti-ß2 glycoprotein-I (anti-ß2-GPI) IgG/M ≥ 40 U. Stable aPL profile was defined as a clinically meaningful aPL profile in at least two-thirds of follow-up measurements. Generalized linear mixed models with logit link were used for primary objective analysis. RESULTS: Of 472 patients with clinically meaningful aPL profile at baseline (median follow-up 5.1 yrs), 366/472 (78%) patients had stable aPL profiles over time, 54 (11%) unstable, and 52 (11%) inconclusive. Time did not significantly affect odds of maintaining a clinically meaningful aPL profile at follow-up in univariate (P = 0.906) and multivariable analysis (P = 0.790). Baseline triple aPL positivity decreased (OR 0.25, 95% CI 0.10-0.64, P = 0.004) and isolated LAC test positivity increased (OR 3.3, 95% CI 1.53-7.13, P = 0.002) the odds of an unstable aPL profile over time. CONCLUSION: Approximately 80% of our international cohort patients with clinically meaningful aPL profiles at baseline remain stable at a median follow-up of 5 years; triple aPL-positivity increase the odds of a stable aPL profile. These results will guide future validation studies of stored blood samples through APS ACTION Core Laboratories.

16th International Congress on Antiphospholipid Antibodies Task Force Report on Obstetric Antiphospholipid Syndrome.

Obstetric antiphospholipid syndrome (APS) remains a clinical challenge for practitioners, with several controversial points that have not been answered so far. This Obstetric APS Task Force met on the 16th International Congress on Antiphospholipid Antibodies in Manchester, England, to discuss about treatment, diagnostic and clinical aspects of the disease. This report will address evidence-based medicine related to obstetric APS, including limitations on our current management, the relationship between antibodies against domain 1 of ß2GPI and obstetric morbidity, hydroxychloroquine use in patients with obstetric APS and factors associated with thrombosis after obstetric APS. Finally, future directions for better understanding this complex condition are also reported by the Task Force coordinators.

"Disease knowledge index" and perspectives on reproductive issues: A nationwide study on 398 women with autoimmune rheumatic diseases.

OBJECTIVE: The reproductive choices of women affected by rheumatic diseases (RD) can be influenced by several factors, including the quality of physician-patient communication. We conducted a survey on reproductive issues aiming at exploring the unmet needs of women with RD during childbearing age. METHODS: We administered 65 multiple-choice and 12 open-answer questions about pregnancy counselling, contraception, use of drugs during pregnancy and other women reproductive issues to 477 consecutive women with RD aged 18-55 years followed-up in 24 rheumatology centres in Italy. Analysis was restricted to 398 patients who received their diagnosis of RD before the age of 45. According to the RD diagnosis, patients were subdivided into 2 groups: connective tissue diseases (n = 249) and chronic arthritis (n = 149). RESULTS: At the time of interview, women in both groups had a mean age of 40 years. Nearly one third of patients in each group declared not to have received any counselling about either pregnancy desire nor contraception. A smaller family size than desired was reported by nearly 37% of patients, because of concerns related to maternal disease in one fourth of the cases. A "Disease Knowledge Index" (DKI) was created to investigate the degree of patients' information about the implications of their RD on reproductive issues. Having received counselling was associated with higher DKI values and with a positive impact on family planning. CONCLUSION: Italian women of childbearing age affected by RD reported several unmet needs in their knowledge about reproductive issues. Strategies are needed to implement and facilitate physician-patient communication.

Limited cutaneous systemic sclerosis skin demonstrates distinct molecular subsets separated by a cardiovascular development gene expression signature.

BACKGROUND: Systemic sclerosis (SSc; scleroderma) is an uncommon autoimmune rheumatic disease characterised by autoimmunity, vasculopathy and fibrosis. Gene expression profiling distinguishes scleroderma from normal skin, and can detect different subsets of disease, with potential to identify prognostic biomarkers of organ involvement or response to therapy. We have performed gene expression profiling in skin samples from patients with limited cutaneous SSc (lcSSc). METHODS: Total RNA was extracted from clinically uninvolved skin biopsies of 15 patients with lcSSc and 8 healthy controls (HC). Gene expression profiling was performed on a DNA oligonucleotide microarray chip. Differentially expressed genes (DEG) were identified using significance analysis of microarrays (SAM). Functional enrichment analysis of gene signatures was done via g:Profiler. RESULTS: There were 218 DEG between lcSSc and HC samples (false discovery rate <10%): 181/218 DEG were upregulated in lcSSc samples. Hierarchical clustering of DEG suggested the presence of two separate groups of lcSSc samples: "limited 1" and "limited 2". The limited-1 group (13 samples, 10 unique patients) showed upregulation of genes involved in cell adhesion, cardiovascular system (CVS) development, extracellular matrix and immune and inflammatory response. The CVS development signature was of particular interest as its genes showed very strong enrichment in response to wounding, response to transforming growth factor (TGF)-ß and kinase cascade. Neither limited-2 samples (six samples, five unique patients) nor HC samples showed functional enrichment. There were no significant differences in demographic or clinical parameters between these two groups. These results were confirmed using a second independent cohort. CONCLUSIONS: Our study suggests the presence of molecular subsets in lcSSc based on gene expression profiling of biopsies from uninvolved skin. This may reflect important differences in pathogenesis within these patient groups. We identify differential expression of a subset of genes that relate to CVS and are enriched in fibrotic signalling. This may shed light on mechanisms of vascular disease in SSc. The enrichment in profibrotic profile suggests that dysregulated gene expression may contribute to vasculopathy and fibrosis in different disease subsets.

Antiphospholipid Antibodies and Infertility: A Gene Expression Study in Decidual Stromal Cells.

BACKGROUND: Antiphospholipid antibodies (aPL) have been advocated as potential mediators of unexplained female infertility, but no evidence has yet been raised to support such an association. OBJECTIVES: To test the hypothesis that aPL might interfere with uterine decidualization, a gene expression study was performed on decidual stromal cells treated with different aPL preparations. METHODS: Decidual stromal cells were isolated from first-trimester deciduas obtained from two women undergoing elective abortion, and treated with: (i) a ß2GPI-dependent aPL monoclonal antibody (IS3); (ii) IS3 plus TIFI, a synthetic peptide mimicking PL-binding region of ß2GPI; and (iii) IgG from healthy subjects (NHS). Gene expression data were acquired using human HT-12 v3 beadchip arrays (Illumina). Differential expression analysis was performed by fitting a gene-wise linear model using the treatment group and decidual source as covariates. RESULTS: In the comparison of IS3 versus IgG NHS-treated decidual cells, gene ontology (GO) enrichment was expressed in terms relating to well-characterized aPL-mediated cellular effects: "inflammatory response," "immune response," "response to stress," "oxydoreductase activity," "metalloendopeptidase activity," and "cytokine/chemokine activity." As expected, almost all genes were up-regulated by IS3 treatment. The same GO categories appeared to be differentially expressed when IS3 treatment was compared to IS3 + TIFI, but with most genes being down-regulated. CONCLUSIONS: Given the inflammatory response evinced on gene expression analysis of decidual stromal cells treated with a ß2GPI -dependent aPL monoclonal antibody, it is feasible that aPL might interfere with uterine decidualization, affecting the early stages of implantation and ultimately resulting in female infertility.

The hidden world of anti-phospholipid antibodies and female infertility: A literature appraisal.

Even though the association of anti-phospholipid antibodies (aPL) with infertility is debated, infertile women are commonly screened for aPL. To review evidence, a systematic PubMed search was conducted to retrieve papers addressing (i) the association between aPL and infertility, (ii) the positivity rate of criteria and non-criteria aPL in women with infertility, (iii) the association between aPL and assisted reproduction technologies (ART) outcome, (iv) the efficacy of medical treatments on ART outcome, and (v) the effects of ART on thrombotic risk. A total of 46 papers were considered; several limitations emerged: (i) wide heterogeneity in study populations, (ii) non-prospective design in 90% of studies, and (iii) aPL cutoffs not conforming to international guidelines in more than 75% of studies; aPL positivity not confirmed in 89% of studies. Most studies evinced an association between infertility and anti-ß2GPI antibodies and almost all non-criteria aPL. The association rate with infertility was below 50% for lupus anti-coagulant, anti-cardiolipin antibodies (aCL), and anti-phosphatidic acid antibodies. According to our estimates, overall positivity rates of criteria and non-criteria aPL tests are 6% and 3% among infertile women, 1% and 2% among controls, respectively. A significant difference in the positivity rate of patients versus controls emerged for aCL only. Five of 18 studies reported a detrimental effect of aPL on ART outcome. Only one of the six studies assessing the effects of treatment on ART outcome among aPL-positive infertile women reported a benefit. All relevant studies reported no increase in the rate of thrombosis among aPL-positive women undergoing ART.

Clinical characterization of antiphospholipid syndrome by detection of IgG antibodies against ß2 -glycoprotein i domain 1 and domain 4/5: ratio of anti-domain 1 to anti-domain 4/5 as a useful new biomarker for antiphospholipid syndrome.

OBJECTIVE: It has been suggested that only antibodies against domain 1 (D1) of ß2 -glycoprotein I (ß2 GPI) are pathogenic and diagnostic. The role of antibodies against other ß2 GPI domains is still debated. This study was undertaken to evaluate the clinical relevance of domain specificity profiling of anti-ß2 GPI IgG antibodies in antiphospholipid syndrome (APS) patients and in control groups of patients with systemic autoimmune rheumatic diseases and in asymptomatic antiphospholipid antibody (aPL) carriers. METHODS: We evaluated 159 subjects with persistently positive, medium or high-titer anti-ß2 GPI IgG, including 56 patients with thrombotic (obstetric or nonobstetric) primary APS, 31 women with obstetric primary APS, 42 aPL-positive patients with systemic autoimmune rheumatic diseases, and 30 asymptomatic aPL carriers. One hundred healthy donors were included. Anti-ß2 GPI D1 and D4/5 IgG were tested on research enzyme-linked immunosorbent assays containing recombinant ß2 GPI domains. RESULTS: As compared to other groups, aPL carriers displayed higher frequency/titer of anti-D4/5 IgG. Unlike anti-D4/5, anti-D1 IgG antibodies were more frequent and at higher titer in triple than in single or double aPL-positive subjects. An anti-D1 to anti-D4/5 ratio of ≥1.5 was predictive of systemic autoimmunity (odds ratio 3.25 [95% confidence interval 1.45-7.49], P = 0.005). Neither anti-D1 nor anti-D4/5 antibodies were associated with APS clinical criteria. CONCLUSION: Anti-D1 IgG is the preferential specificity not only in vascular and obstetric primary APS, but also in patients with systemic autoimmune rheumatic disease with no clinical features of APS. Conversely, aPL carriers do not have a polarized profile toward D1. Combined testing for anti-ß2 GPI IgG with different domain specificity allows a more accurate aPL profiling, with polarization toward anti-D1 IgG as a possible fingerprint of systemic autoimmunity.