APS is an autoimmune disorder that causes an increased risk for developing a venous or arterial thromboembolism, as well as recurrent miscarriages. APS frequently occurs in people with lupus, and is referred to as secondary APS in this case. Many people who have APS, however, do not have another autoimmune disorder, and their disease is referred to as primary APS. APS may be a genetic disorder, and identifying the gene(s) that predisposes an individual to develop it could lead to a better understanding of the disease, as well as improved therapies. This study will use a genetic strategy to identify potential risk factors for the development of APS by recruiting people with APS who have family members who are either affected by the syndrome or who have another autoimmune disorder. The results of the genetic testing will be compared among the following two groups of families: people with APS who also have one or more of their family members affected specifically by APS; and people with APS who also have one or more of their family members affected by another type of autoimmune disorder, such as lupus or rheumatoid arthritis.

Participants in this study will perform a pre-screening questionnaire over the phone to determine relevant clinical diagnoses and collect a brief family history of autoimmune disorders. Eligible participants will receive an enrollment package in the mail. If possible, participants will then report to the study site to supply a detailed family and medical history and provide a blood sample for analysis for antiphospholipid antibodies and preparation of genomic DNA. If participants are unable to attend the study visit, the interviews will be conducted over the phone. Those who are unable to attend the site visit will receive a blood enrollment kit in the mail, and these participants will report to a convenient location for phlebotomy services. Participants who have already provided blood samples for the APS Collaborative Registry (APSCORE) may not have to provide another sample for this study. Information collected for statistical analysis will include the following data: demographic information; co-morbid conditions and chronic risk factors; lipid profile; history of recurrent infections, renal failure, and cardiovascular disease; height and weight; details of any medications and supplements currently being taken; venous and arterial thromboembolic events; and any history of adverse pregnancy outcomes.