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Aims: The identification of haemophagocytosis in bone marrow (BM) is recurrently identified in patients with severe COVID-19. These initial COVID-19 autopsy studies have afforded valuable insight into the pathophysiology of this disease; however, only a limited number of case series have focused on lymphoid or haematopoietic tissues., Methods: BM and lymph node (LN) specimens were obtained from adult autopsies performed between 1 April 2020 and 1 June 2020, for which the decedent had tested positive for SARS-CoV-2. Tissue sections (H&E, CD3, CD20, CD21, CD138, CD163, MUM1, kappa/lambda light chains in situ hybridisation) were examined by two haematopathologists, who recorded morphological features in a blinded fashion. Haemophagocytic lymphohistiocytosis (HLH) was assessed based on HLH 2004 criteria., Results: The BM demonstrated a haemophagocytic pattern in 9 out of 25 patients (36%). The HLH pattern was associated with longer hospitalisation, BM plasmacytosis, LN follicular hyperplasia and lower aspartate aminotransferase (AST), as well as ferritin at demise. LN examination showed increased plasmacytoid cells in 20 of 25 patients (80%). This pattern was associated with a low absolute monocyte count at diagnosis, lower white cell count and lower absolute neutrophil count at demise, and lower ferritin and AST at demise., Conclusions: Autopsy results demonstrate distinct morphological patterns in BM, with or without haemophagocytic macrophages, and in LN, with or without increased plasmacytoid cells. Since only a minority of patients met diagnostic criteria for HLH, the observed BM haemophagocytic macrophages may be more indicative of an overall inflammatory state., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Pathology and Monkeypox virus (MPXV) tissue tropism in severe and fatal human mpox is not thoroughly described but can help elucidate the disease pathogenesis and the role of coinfections in immunocompromised patients., Methods: We analyzed biopsy and autopsy tissues from 22 patients with severe or fatal outcomes to characterize pathology and viral antigen and DNA distribution in tissues by immunohistochemistry and in situ hybridization. Tissue-based testing for coinfections was also performed., Results: Mucocutaneous lesions showed necrotizing and proliferative epithelial changes. Deceased patients with autopsy tissues evaluated had digestive tract lesions, and half had systemic tissue necrosis with thrombotic vasculopathy in lymphoid tissues, lung, or other solid organs. Half also had bronchopneumonia, and one-third had acute lung injury. All cases had MPXV antigen and DNA detected in tissues. Coinfections were identified in 5 of 16 (31%) biopsy and 4 of 6 (67%) autopsy cases., Conclusions: Severe mpox in immunocompromised patients is characterized by extensive viral infection of tissues and viremic dissemination that can progress despite available therapeutics. Digestive tract and lung involvement are common and associated with prominent histopathological and clinical manifestations. Coinfections may complicate mpox diagnosis and treatment. Significant viral DNA (likely correlating to infectious virus) in tissues necessitates enhanced biosafety measures in healthcare and autopsy settings., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2024.)

Collagenous gastritis has been reported as a rare cause of nausea, diarrhea, weight changes, and early satiety in female patients. Here, we describe two women aged 43 and 71 years who presented with similar symptoms. Gastric biopsies from both individuals showed thickened, irregular subepithelial collagen bands (>10  μ m). The pathogenesis of collagenous gastritis is poorly understood, but it may be the presenting symptom for many underlying autoimmune conditions. In particular, there is a well-established connection between collagenous disorders of the gastrointestinal tract and celiac sprue, Sjögren syndrome, and lymphocytic colitis; however, none of these conditions had been diagnosed in our patients. The older woman had incidentally discovered hypogammaglobinemia and IgA deficiency, whereas the younger woman suffered from fibromyalgia. Although a gluten-free diet and budesonide have been effective in some cases, there is no standardized therapy for collagenous gastritis. Our patients trialed diet modification and have required no additional medical interventions., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2023 Mark G. Evans et al.)