Self-reported race/ethnicity derives from multiple-choice selection of US Census-standardized terms and does not fully capture the complexity of participant racial identity. CCHMC = Cincinnati Children’s Hospital Medical Center; KPW/UW = Kaiser Permanente Washington / University of Washington; CHOP = Children’s Hospital of Philadelphia. Sequencing Centers (SCs, italics): The Baylor College of Medicine Human Genome Sequencing Center [BCM-HGSC], Houston TX; Broad Institute and Partners Laboratory for Molecular Medicine [LMM], Cambridge, MA.