Antiphospholipid Syndrome (APS) ACTION Plaquenil

Inclusion Criteria:

• Age 18-60

• Persistent (at least 12 weeks apart) aPL-positivity within 12 months prior to thescreening defined as:

• aCL IgG/M (> 40U, medium-to-high titer, and/or greater than the 99th percentile)and/or

• aβ2GPI IgG/M (>40U, medium-to-high titer, and/or greater than the 99th percentile)and/or

• Positive LA test based on the International Society of Thrombosis & HaematosisRecommendations

Exclusion Criteria:

• History of thrombosis (arterial, venous, and/or biopsy proven microthrombosis)

• Of note, history of superficial thrombophlebitis is not an exclusion criterion.

• History of Transient Ischemic Attack Confirmed by a Neurologist

• SLE Diagnosis based on the ACR Classification Criteria > 4/11

• Other Systemic Autoimmune Diseases diagnosed based on ACR Classification Criteria (e.g., RA, Systemic Vasculitis, Spondylarthropathy, Systemic Sclerosis, InflammatoryMuscle Disease, Sjogren Syndrome, Mixed Connective Tissue Disorder)

• Current HCQ or another antimalarial treatment (-3 months)

• Current warfarin treatment (- 3 months)

• Current heparin therapy (- 3 months)

• Current pregnancy

• Acute seizure within 7 days prior to screening (contraindication for HCQ treatment)

• Psoriasis (contraindication for HCQ treatment)

• History of HCQ eye toxicity

• History of Hydroxychloroquine allergy

• Liver disease with AST or ALT two times of the upper limit

• Known glucose-6-phosphate dehydrogenase deficiency

• Known malignancy (with the exception of non-metastatic squamous cell and basal cellskin carcinomas)

• Alcoholism (chronic alcohol abuse)

• Known illicit drug abuse

• Patient refusal

• Inability to comply with study and follow-up procedures