PMC9278803_01
Pathological analysis. (A, B) Aortic valve with Whipple's endocarditis: superficial vegetation and fibrosis of the connective valve tissue and mononuclear inflammatory cell infiltrate with numerous foamy macrophages near the vegetation (A, arrow) and with large eosinophilic deposits in the connective valve tissue (arrowheads, B) (hematoxylin-eosin-saffron, original magnification x100 and x100, respectively). (C, D) Foamy macrophages containing the characteristic inclusion bodies (C, arrow) and with massive extracellular detection of bacilli with the PAS stain (D, arrowheads) (PAS staining, original magnification x100 and x100, respectively). (E, F) Immunohistochemical detection of Tropheryma whipplei: bacilli are packed as coarse granular immunopositive material in foamy macrophage cytoplasm (E, arrow) and in an extracellular location in the connective valve tissue in massive number (F, arrowheads) (polyclonal rabbit anti-T. whipplei antibody used at a dilution of 1:2,000 with Mayer's hemalum counterstain, original magnification x100 and x100, respectively).
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Tropheryma whipplei-infected aortic valve showed typical histologic features related to infective endocarditis, with vegetation and inflammatory infiltrates in fibrotic tissue (Figures 1A, B). The foamy histiocytes were stuffed with a dense, granular material that was strongly positive on PAS staining and resistant to diastase (Figure 1C). Moreover, a massive PAS-positive deposit material was also observed in the valvular connective tissue with an extracellular location (Figure 1D). Bacilli were observed as immunopositive material, both in foamy macrophage cytoplasm and in extracellular location (Figures 1D-F).
Scanning electron microscopy of Tropheryma whipplei vegetation. (A) Low-magnification view of the whole cardiac biopsy piece along its deepness, with vegetation (right) superposed to valve leaflet (left). (B) Zoom-in image of the [B] boxed region in (A) showing a cluster of extracellular T. whipplei cells embedded in the valvular tissue. (C) Zoom-in image of the (C) boxed region in (A) showing extracellular T. whipplei cells (bold arrows) disseminated in a network of thick fibrin bundles and platelets (thick arrow). (D) Zoom-in image of the (D) boxed region in (A) with extracellular T. whipplei cells located in a fishnet-like network of fibrin filaments. (E, F) Zoom-in image of the (E, F) boxed region in (A) containing erythrocytes (E, F), isolated or aggregated platelets (E, F, *), fibrin, and extracellular T. whipplei cells (arrows). (G-I) Zoom-in image of the (G-I) boxed region in (A) depicting a more central region of the vegetation with numerous T. whipplei cells, intermingled with an amorphous matrix and focally organized (G) or more broadly distributed (H, I).
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SEM analysis was performed on a valvular piece consisting in vegetation anchored to the valve leaflet (Figure 2A). T. whipplei bacteria were found embedded in the leaflet tissue (Figure 2B). Tropheryma whipplei bacteria were also located extracellularly within the vegetation: i) in the peripheral areas of the vegetation, arranged as single cells disseminated within the other elements of the vegetation (Figures 2C-F), and ii) in deeper regions composed exclusively of T. whipplei cells, giving the appearance of "vermicelli" (Figures 2G-I). In these deep foci, T. whipplei cells were densely packed, embedded in an amorphous matrix, and spatially arranged with mixed orientations (Figures 2G-I).