Registry participants will have a blood sample drawn and will be interviewed about their medical histories. Participants will be asked to return for a follow-up visit after two years. Clinical, demographic, and laboratory data will be collected. Registry resources will be made available to researchers and medical practitioners to support a broad range of research on the causes, diagnosis, mechanisms, and treatment of APS. The University of North Carolina at Chapel Hill is the coordinating center and an enrollment site for the registry. There are seven other enrollment sites: Ball Memorial Hospital, Muncie, IN; Duke University, Durham, NC; Hospital for Special Surgery, New York, NY; Johns Hopkins University, Baltimore, MD; Morehouse School of Medicine, Atlanta, GA; University of Texas Health Science Center, San Antonio, TX; and University of Utah Health Science Center, Salt Lake City, UT.
Inclusion Criteria: * Antiphospholipid antibodies with or without associated clinical manifestations