1. From the Departments of Pediatrics (L.G.), Radiology (R.L.C.), Medicine (G.K.R., S.B.), and Pathology (E.I.A.), Massachusetts General Hospital, and the Departments of Pediatrics (L.G.), Radiology (R.L.C.), Medicine (G.K.R., S.B.), and Pathology (E.I.A.), Harvard Medical School — both in Boston; and the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD (S.M.H.).