Genetic Risk Factors Associated With Antiphospholipid Antibody Syndrome

Inclusion Criteria: * Persistent presence of an antiphospholipid antibody, as defined by one or both of the following criteria: 1. Medium or high anticardiolipin antibody level in the blood on two or more occasions at least 6 weeks apart 2. Presence of lupus anticoagulant in the plasma on two or more occasions at least 6 weeks apart * Presence of clinical symptoms seen in patients with APS, including vascular thrombosis (one or more clinical episodes of arterial, venous, or small vessel thrombosis in any tissue or organ) and/or pregnancy morbidity, defined as any of the following: 1. One or more unexplained deaths of a morphologically normal fetus at or beyond the 10th week of gestation, with normal fetus morphology documented by ultrasound or direct examination or the fetus 2. One or more premature births of a morphologically normal baby at or before the 34th week of gestation because of severe pre-eclampsia, eclampsia, or severe placental insufficiency 3. Three or more unexplained consecutive spontaneous abortions before the 10th week of gestation, with maternal anatomic or hormonal abnormalities and paternal and maternal chromosomal causes excluded * People who have elevated antiphospholipid antibody levels but do not fully meet clinical criteria for APS, and do have affected family members, will be considered for enrollment Exclusion Criteria: * No documented presence of antiphospholipid antibody