Clinical Research Directory

INCLUSION CRITERIA: 1. Group 1 \[APS\]: Patients fulfilling the classification criteria for antiphospholipid syndrome (seropositive APS, SP-APS) 2. Group 2 \[SN-APS\]: patients with seronegative APS (SN-APS): with clinical criteria (thrombotic or obstetric) for APS, persistently negative for aPL, and with clinical features highly suggestive of APS (recurrent events, thrombotic + obstetrical events, extra-criteria manifestations, other autoimmune diseases) 3. Group 3: patients with clinical criteria (thrombotic or obstetric) for APS, negative for aPL, but without clinical features highly suggestive of APS (recurrent events, thrombotic + obstetrical events, extra-criteria manifestations, other autoimmune diseases). 4. Age \< 65 years (at event time) 5. Less than 5 years from the first even EXCLUSION CRITERIA 1. Group 2 and 3: patients with a known cause of thrombosis or obstetrical manifestations 2. Deceased patients 3. Less than 5 years from the first event