Lymphofollicular lesions associated with monkeypox (Mpox) virus proctitis

Abstract

In the recent 2022 monkeypox (Mpox) global outbreak, cases have been mostly documented among men who have sex with men. Proctitis was reported in almost 14% of cases. In this study, four Mpox-confirmed cases requiring hospitalizations for severe proctitis were characterized by clinical, virological, microbiological, endoscopic, and histological aspects. The study showed the presence of lymphofollicular lesions associated with Mpox virus rectal infection for the first time.

Keywords: Lymphofollicular hyperplasia; Monkeypox (mpox); Outbreak; PTGC; Proctitis.

Figure 1

Endoscopic and histopathological findings. (a) Representative endoscopic image shows edematous rectal mucosa sprinkled with small surface erosions. (b,c) Representative micrographs of hematoxylin and eosin stained sections: (b) Crypt epithelial cells displaying signs of viral cytopatic changes: loss of cell polarity, nuclei dislocation with irregular contours and prominent nucleoli, vacuolization of cytoplasm (arrows); (c) Intramucosal isolated hyperplastic follicle showing PTGC, with irregular demarcation of germinal center and mantle zone (light zone and dark zone) (asterisk). (d-i) Immunohistochemical characterization of PTGC: (d,e) prominent and irregular lymphoid follicle display dispersion of CD3 positive T cells (d), and B cells CD20 positive extending into the germinal center (e); (f,g) germinal center appear predominantly composed of mantle zone B lymphocytes that are BCL2 positive cells (f), with few residual germinal center cells, highlighted by BCL6 positivity (g); (h,i) CD23 immunolabeling shows disruption of follicular dendritic cells network into clusters (i, higher magnification of squared area in h). Bars: b = 50 µm; c = 100 µm; d, e, h = 200 µm; f, g. i = 50 µm. CD, clusters of differentiation; PTGC, progressive transformation of the germinal centers.