Long-term use of hydroxychloroquine reduces antiphospholipid antibodies levels in patients with primary antiphospholipid syndrome.

Hydroxychloroquine (HCQ) was suggested to play a role in lowering antiphospholipid antibody titers and preventing thrombotic recurrences in patients with systemic lupus erythematosus, but few data are available in patients with primary antiphospholipid syndrome (PAPS). In this retrospective, propensity score-matched cohort study, we evaluated the impact of HCQ on aPL titers and the incidence of thrombotic events in 57 exposed patients compared to 57 not exposed patients. These were matched for sex/type of disease onset/follow-up duration, age at the beginning of the follow-up ±10 years and initial date of the follow-up ±5 years. At baseline, no significant differences in demographical, clinical and serological features were observed between the two groups except for positive anti-extractable nuclear antigen antibodies (21 % in HCQ exposed vs 0 % in HCQ not exposed, P = 0.001). Both the levels of IgG anti-cardiolipin and IgG/IgM anti-β2-glycoprotein I (anti-β2GPI) were significantly reduced at end of follow-up compared to the baseline in HCQ-exposed patients, while there were no differences in the other group. Moreover, anti-β2GPI IgG titers were significantly decreased when the end of follow-up was compared between the two groups (P < 0.002). Among patients with a history of thrombosis, the annual incidence of recurrence was 1.16 % in HCQ exposed and 1.71 % in not exposed patients, with a significant reduction in the incidence of arterial events (0 vs 1.14 %). This study shows a strong reduction in aPL titers together with an apparent decrease in the incidence of arterial thrombosis recurrence in PAPS patients treated with HCQ.