Participating relatives will undergo a medical and family history, possibly with a review of medical records, physical examination, blood and urine tests. Additional procedures may include a 24-hour urine collection, X-rays, and consultations with medical specialists. A DNA sample (blood or saliva) will also be collected for genetic studies. Additional blood samples of no more than 550 mL during an 8-week period may be requested for studies of white cell adhesion (stickiness).