1. From the Department of Laboratories (Drs Dickerson, Cole, Jack, Rutledge, and Astion and Mss Conta and Wellner) and the Division of Genetic Medicine (Dr Wallace), Seattle Children's Hospital, Seattle, Washington; the Departments of Laboratory Medicine (Drs Dickerson, Jack, Rutledge, and Astion) and Pathology (Dr Cole), University of Washington, Seattle; and the Department of Pediatrics, University of Washington School of Medicine, Seattle (Dr Wallace).