Severe histologic sequelae in the CNS of patients with TA-TMA. Cerebral (A-B; original magnification ×8 (A), original magnification ×40 (B)) and cerebellar (C-D; original magnification x20.5 (C), original magnification ×2.5 (D)) white matter show extensive demyelination, with scattered macrophages (C, yellow arrow, original magnification ×20.5), though not to confluence and not an infarct microscopically or in vascular distribution. Many vessels are affected by chronic changes in other organs that are related to TA-TMA. (C) Capillaries with thickened rigid walls shown at low power, appearing “wire-like” with a ratio of wall to lumen to wall occasionally 1:1:1 (red arrow) are present. (A-C) Capillary basement membrane layering and splitting and pericapillary clearing are also seen (light blue arrows and most pronounced, dark blue arrow). A range of capillaries and small arteries show similar features. Pigment is seen in small capillaries (A, orange arrows) and macrophages are present in the periarteriolar stroma (A, green arrow). (E-F; original magnification ×1.8 (E), original magnification ×8.5 (F)) Loss of myelination is readily evident on Luxol fast blue stain with periodic acid–Schiff highlighting vascular features. (G-J) These findings were compared with the histology in a patient without TA-TMA. There were normal delicate capillaries (red arrows) and tracks (blue arrows), as well as preserved parenchyma in cerebellar (G-H; original magnification x13 (G), original magnification ×40 (H)) and cerebral white (I, original magnification ×40) matter and spinal cord (J, interface of white and gray matter, original magnification ×14/×0.4).