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Objective: The release of neutrophil extracellular traps (NETs) by hyperactive neutrophils has recently been recognized to play an important role in antiphospholipid syndrome (APS). This study was undertaken to evaluate autoantibodies targeting NETs in patients with primary APS, and to determine their potential functions and clinical associations., Methods: We measured global anti-NET activity in 76 patients with primary APS, 23 patients with systemic lupus erythematosus without antiphospholipid antibodies (aPL), 11 patients with a history of unprovoked venous thrombosis without aPL, and 44 healthy controls. The ability of APS sera to degrade NETs was also assessed., Results: We found markedly elevated levels of anti-NET IgG and IgM in patients with primary APS compared with healthy controls (for IgG, mean ± SD optical density 0.55 ± 0.34 versus 0.33 ± 0.17; for IgM, mean ± SD optical density 0.76 ± 0.51 versus 0.26 ± 0.23). This anti-NET activity did not correlate with levels of traditional aPL and was relatively stable over time. Mechanistically, anti-NET antibodies (especially of the IgG isotype) impaired the ability of patient sera to degrade NETs (r = 0.4, P = 0.003). Levels of anti-NET IgM inversely correlated with complement C4 (r = 0.4, P = 0.019). Clinically, anti-NET antibodies associated with certain APS clinical manifestations, and in particular recurrent venous thrombosis (odds ratio 4.3; P = 0.002). Interestingly, anti-NET antibody levels also appeared to be associated with unprovoked venous thrombosis in the general population (for IgM, mean ± SD optical density 0.67 ± 0.34 versus 0.26 ± 0.23)., Conclusion: Our data indicate high levels of anti-NET antibodies in patients with primary APS, which may impair NET clearance and activate the complement cascade. These findings may ultimately enable more effective risk stratification., (© 2020, American College of Rheumatology.)

Objectives: We assessed the burden of systemic lupus erythematosus (SLE) among Arab and Chaldean Americans residing in southeast Michigan., Methods: For those meeting SLE criteria from the Michigan Lupus Epidemiology and Surveillance Registry, we determined Arab or Chaldean ethnicity by links with demographic data from birth certificates and with a database of Arab and Chaldean names. We compared prevalence and incidence of SLE for Arab and Chaldean Americans with estimates for non-Arab and non-Chaldean American Whites and Blacks., Results: We classified 54 individuals with SLE as Arab and Chaldean Americans. The age-adjusted incidence and prevalence estimates for Arab and Chaldean Americans were 7.6 and 62.6 per 100 000, respectively. Arab and Chaldean Americans had a 2.1-fold excess SLE incidence compared with non-Arab and non-Chaldean American Whites. Arab and Chaldean American women had both significantly higher incidence rates (5.0-fold increase) and prevalence estimates (7.4-fold increase) than did Arab and Chaldean American men., Conclusions: Recognizing that Arab and Chaldean Americans experience different disease burdens from Whites is a first step toward earlier diagnosis and designing targeted interventions. Better methods of assigning ethnicity would improve research in this population.