Fulminant demyelinating encephalomyelitis

The biopsy specimen revealed a small actively demyelinating lesion (A, arrow in the magnified section indicates macrophages containing LFB-positive myelin degradation products) and inflammatory infiltrates composed of CD68-positive macrophages (B), and CD8-positive T cells (C). One vessel showed perivascular deposits of activated complement complex C9neo (D, arrows). The autopsy tissue showed confluent demyelinating lesions in the brain that were immunohistochemically characterized by loss of MBP (E, rectangle enlarged in H) but contained large preoligodendrocytes that strongly labeled for CNPase (F, rectangle enlarged in I) while MOG was almost negative (G, rectangle enlarged in J; lesion borders highlighted with dotted lines). The inflammatory infiltrates mainly contained CD3-positive (K) and CD8-positive (L) T cells and perivascular CD79a-positive B cells (M). The lesion in the optic chiasm showed perivascular deposits of activated complement complex C9neo (N, arrows) and was characterized by a destructive tissue injury with loss of astrocytes in the anti-AQP4 (O), AQP1 (P), and GFAP staining (Q). One plaque in the medulla oblongata showed a selective loss of AQP4 (R; lesion border highlighted with dotted lines) while AQP1 (S) and GFAP (T) were still preserved. The astrocytes in this lesion showed clasmatodendrosis with beading or loss of processes resulting in rounded astrocytes (T, magnified sections). Magnification: E–G: ×40; A and O–T: ×100; B–D: 200×; H–N and magnified section in T: 400×; magnified section in A: 600×. AQP = aquaporin; CNPase = 2',3'-cyclic-nucleotide 3'-phosphodiesterase; GFAP = glial fibrillary acid protein; LFB = Luxol fast blue; MBP = myelin basic protein; MOG = myelin oligodendrocyte glycoprotein.