Histopathology. (A) Preserved liver parenchyma with an inflammatory focus within the lobule, associated with clusters of foamy macrophages containing finely granular golden brown pigment, which was positive with PAS stain and negative with Perls stain for iron. These appearances are characteristic of chronic granulomatous disease (hematoxylin and eosin [H&E] stain). (B) Skin biopsy demonstrating spongiosis of the epidermis with basal vacuolization, dyskeratosis, and a lymphocytic infiltrate of the papillary dermis. Pigment incontinence is also seen within the papillary dermis. These features are consistent with GVHD (H&E stain). (C) Bowel mucosa with crypts shows intraepithelial vacuoles, filled with karyorrhectic debris. These apoptotic bodies are numerous, and intraepithelial lymphocytes are also present. There is scant inflammation within the lamina propria. These features are consistent with GVHD (H&E stain). (D) Postmortem lung parenchyma with muscular arteries shows concentric cellular intimal proliferation. There is almost complete occlusion. Within the airspaces, there is degenerating fibrin. No acute inflammation was present (H&E stain). (E) The corresponding elastic Van Gieson stain of panel D confirms the concentric intimal proliferation. These findings are of severe pulmonary arterial vasculopathy (EVG stain). (F) Postmortem bowel, with extensive necrosis and loss of the normal mucosa. Bacterial colonies are seen, and even at this low power, hemorrhage can be appreciated within the submucosa, which also appears expanded and fibrotic. The muscularis propria appears ragged. These features are of hemorrhagic necrosis, resultant from TMA (H&E stain). (G-H) A high-power view of the submucosa from panel F, highlighting a vessel with eccentric partial occlusion due to thrombus adherent to the wall. A similar vessel is seen in panel H, which is occluded and contains macrophages. These features are related to the underlying vasculopathy (H&E stain). Scale bars, 500 μm (A) and 100 μm (B-H).