A Massive Number of Extracellular Tropheryma whipplei in Infective Endocarditis: A Case Report and Literature Review

Abstract

Whipple's disease (WD) is a chronic multisystemic infection caused by Tropheryma whipplei. If this bacterium presents an intracellular localization, associated with rare diseases and without pathognomonic signs, it is often subject to a misunderstanding of its physiopathology, often a misdiagnosis or simply an oversight. Here, we report the case of a patient treated for presumed rheumatoid arthritis. Recently, this patient presented to the hospital with infectious endocarditis. After surgery and histological analysis, we discovered the presence of T. whipplei. Electron microscopy allowed us to discover an atypical bacterial organization with a very large number of bacteria present in the extracellular medium in vegetation and valvular tissue. This atypical presentation we report here might be explained by the anti-inflammatory treatment administrated for our patient's initial diagnosis of rheumatoid arthritis.

Keywords: Tropheryma whipplei; electron microscopy; infectious endocarditis; rheumatoid arthritis; tocilizumab.

Figure 1

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 ×100 and ×100, 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 ×100 and ×100, 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 ×100 and ×100, respectively).

Figure 2

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).