Background: Diseases related to the immune system, blood clots, and blood vessels can affect every part of the body. These diseases are now known to be interrelated: People who have strokes, blood clots in their legs, or autoimmune disease, for example, are at greater risk of complications in the heart, brain, and other organs. Researchers want to learn more about how these diseases start, how they change over time, and how they affect different organs.

Objective: To learn more about how inflammation and diseases of the blood vessels start and how they change over time.

Eligibility: People aged 5 years and older with a disease related to blood clots, the immune system, or blood vessels. Healthy relatives of people with these diseases and unrelated healthy volunteers are also needed.

Design: Participants will have a baseline visit: They will provide a medical history, physical exam and blood test. All other tests and procedures are optional; these may be spread over more than 1 day: Tests of heart and lung function. Fill in a family tree form. Imaging scans Treadmill or bike stress tests and a 6-minute walk test. Tests of blood pressure and the flow of blood through vessels. Photos of the face and body. Eye exams, with photos taken of the retina. Saliva and urine samples. Biopsies (tissues samples) of the skin and fat. Tests of thinking and mental function. Evaluations by other medical specialists. Participants may opt to return for repeat testing for up to 90 months (7.5 years). Some visits may be done by telehealth.