Electron microscope examination of microvasculature in the brain from MPS III D patient. Representative longitudinal capillaries of control putamen (A), hippocampus (D), cerebellum (G), and motor cortex (J) were characterized by normal ultrastructural appearance indicating intact BBB. In MPS III D patient, capillaries in the putamen (B, C), hippocampus (E, F), cerebellum (H, I), and motor cortex (K, L) showed swollen EC narrowing the lumen or necrotic EC separating from the BM. Completely degenerated pericyte, perivascular edema, and vacuoles or autophagosomes in EC were also observed. Some capillaries displayed ruptured degenerated pericytes releasing zebra bodies into extracellular space (F, K). Capillaries also showed large collagen accumulations separating the BM (E, H) and swollen endothelium with lipid inclusion (H). Large areas of extracellular edema were observed surrounding capillaries and free floating swollen mitochondria in the space occupied by degenerated astrocyte foot processes. EC - endothelial cell, BM - basement membrane, A – axon, P – pericyte, Nu – nucleus, M – mitochondrion, V – vacuole, Aph – autophagosome, Pl – platelets, Coll – collagen accumulation, L – lipid inclusion, * - separation of EC from BM or P, + - extracellular edema, ! – ruptured pericyte. Magnification in (A), (G) is 3,500; in (B), (C), (L) is 8,900; in (D) is 2,200; in (E) is 1,800; in (F), (I), (K) is 7,100; in (H) is 5,600; in (J) is 4,400.