Brain MRIs of patients 1, 3, and 8. Coronal brain MRIs of patients P1 (taken at age 20 months, 11 months after HSCT), P3 (age 6 years, 2 months before HSCT), and P8 (age 3 years, 3 months after HSCT). T2-weighted images are shown for P1, and fluid attenuation inversion recovery (FLAIR) images are shown for P3 and P8. (A) Bilateral, abnormal hyperintensities in the periventricular white matter (arrows) and the anterior part of the corpus callosum. (B) Abnormal hyperintensities in the white matter, the periventricular area but not of the U fibers (arrows), and a unilateral signal abnormality in the basal ganglia (the caudate nucleus in P3 and the putamen in P8; arrowheads). (C) White matter abnormalities in the cerebellum (arrows).