[Diagnostic value of intestinal tissue metagenomic next-generation sequencing in severe diarrhea following haploidentical hematopoietic stem cell transplantation].

Objective: To evaluate the diagnostic value of intestinal tissue metagenomic next-generation sequencing (mNGS) in severe diarrhea following haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT) . Methods: Sixteen patients who developed severe diarrhea or hematochezia after haploidentical allo-HSCT at the First Affiliated Hospital of Fujian Medical University (June 2023-August 2024) were enrolled. All underwent gastrointestinal endoscopy and mNGS for microbial detection. Clinical, endoscopic, pathological, and microbiological data were analyzed to evaluate the diagnostic value of mNGS and treatment outcomes following targeted therapy. Results: The study included 16 patients (12 males, 4 females; median age 32.5 years, range 3-60 years). Diarrhea occurred a median of 3.93 months post-transplant (range 1.63-10.40 months). Stool cultures were negative except for one case with Candida. One patient tested positive for Clostridium difficile antigen. Endoscopy revealed mucosal congestion, edema, erosion, and bleeding, with focal inflammation on pathology. mNGS detected pathogens in 87.5% (14/16) of cases, including mixed infections in 78.5% (11/14). Common pathogens were Klebsiella pneumoniae, Enterococcus faecium, Escherichia coli, Rhizopus microsporus, EBV, and CMV. Targeted treatment adjustments led to symptom improvement in 87.5% of patients. Conclusion: Allo-HSCT patients are prone to infectious diarrhea due to immunosuppression. Molecular analysis of endoscopic biopsy tissues using mNGS can accurately identify pathogens, guide targeted therapy, and improve clinical outcomes.