A 79-year-old retired farmer from rural Shandong Province presented with 4 days of high fevers and a preceding month of intermittent syncope. He was pale, febrile, and had scattered lymphadenopathy on imaging. Initial microbiologic testing, including blood and bone marrow cultures and Widal serology, failed to identify Salmonella, and the admission exam did not note any eschar. The source reported that only after targeted next-generation sequencing (NGS) identified Orientia tsutsugamushi did clinicians perform a directed reexamination and find a concealed 5-mm popliteal eschar with central necrosis. The authors emphasized that careful inspection of concealed skin sites in endemic regions such as Shandong remains an accessible, high-yield diagnostic step.
Bone marrow aspirate displayed clusters of large macrophages whose cytoplasm was filled with fine eosinophilic granules. Those cells were morphologically indistinguishable from the classic typhoid cells historically associated with Salmonella enterica serovar Typhi infection. Hemophagocytosis of erythrocytes and platelets was also evident, and the patient developed worsening thrombocytopenia over several days. While the marrow appearances strongly suggested enteric fever on morphology alone, the clinical picture lacked typical enteric symptoms—no abdominal pain, no diarrhea, no rose spots—and standard culture-based and serologic tests did not support Salmonella infection.
Because conventional testing was unrevealing, the team sent the bone marrow aspirate for targeted NGS. The result, available on hospital day 6, detected Orientia tsutsugamushi. The source article reports that the targeted NGS sequence data were deposited in the National Center for Biotechnology Information Sequence Read Archive (BioProject accession and BioSample accession provided in the original text). With the molecular diagnosis in hand, clinicians reexamined the patient and found the previously overlooked popliteal eschar. The patient later recalled gardening barefoot and wearing shorts but did not remember an insect bite. The sequence-based identification shifted the working diagnosis from enteric fever to scrub typhus.
Following targeted identification, the patient received intravenous doxycycline as reported in the source. Fever abated within 48 hours of initiating therapy. Laboratory recovery occurred rapidly: platelet count rose from 60,000/µL to 152,000/µL by hospital day 7, and transaminases normalized in the same timeframe. At three-week follow-up, syncopal episodes had not recurred, and the patient began specific therapy for his concurrently diagnosed myelodysplastic syndrome (MDS) with SF3B1 mutation and ring sideroblasts identified on marrow. The authors attribute the acute, reversible component of the pancytopenia primarily to scrub typhus–associated hemophagocytosis rather than MDS.
The case demonstrates that scrub typhus can produce bone marrow macrophages that closely mimic typhoid cells, expanding the known morphologic spectrum of scrub typhus bone marrow pathology. The authors noted that marrow typhoid cells have long been treated as relatively specific for enteric fever, but when those cells appear without microbiologic evidence of Salmonella, clinicians should consider alternative intracellular pathogens, including Orientia tsutsugamushi. The patient also met multiple criteria consistent with secondary hemophagocytic lymphohistiocytosis; the article cites a systematic review showing many patients recover with anti-rickettsial antibiotics alone.
Several limitations were recognized in the report. The source states that whether other intracellular pathogens can produce identical marrow macrophages has not been systematically examined. Myelodysplastic syndrome with SF3B1 mutation was a coexisting diagnosis and a potential confounder for cytopenias; the authors argued, however, that the rapid hematologic and biochemical response to doxycycline indicated a dominant role for scrub typhus in the acute presentation. Finally, the initial failure to inspect concealed skin sites delayed recognition of a classic clinical sign; this omission illustrates an avoidable diagnostic gap, especially in endemic regions.
The report ends by calling attention to these specific clinical lessons and unanswered questions documented in the source: whether typhoid-like marrow cells occur with other intracellular infections, and how best to integrate molecular diagnostics with focused physical examination in patients who are older or immunocompromised.