{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T13:22:27Z","timestamp":1788268947208,"version":"build-2803163510"},"reference-count":9,"publisher":"American Society for Microbiology","issue":"5","license":[{"start":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T00:00:00Z","timestamp":1788220800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T00:00:00Z","timestamp":1788220800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["ASM Case Rep"],"published-print":{"date-parts":[[2026,9,1]]},"abstract":"ABSTRACT<\/jats:title>\n \n \n \n Background<\/jats:title>\n \n Babesia microti<\/jats:italic>\n , a parasite transmitted by the\n Ixodes scapularis<\/jats:italic>\n tick, can cause infections ranging in presentation from asymptomatic to fulminant, life-threatening disease. Ocrelizumab, an anti-CD20 B-lymphocyte monoclonal antibody used to treat multiple sclerosis, increases the risk of severe or relapsing infections with tick-borne pathogens. In rare cases, babesiosis may trigger hemophagocytic lymphohistiocytosis (HLH).\n <\/jats:p>\n <\/jats:sec>\n \n Case Summary<\/jats:title>\n \n We report a case of babesiosis manifesting in a subacute fashion with secondary HLH in a 51-year-old female on B cell-depleting therapy. She presented in December with generalized weakness and fever and was found to have pancytopenia, transaminitis, and hyperinflammatory markers consistent with HLH. A microbial cell-free DNA next-generation sequencing test detected\n Babesia microti<\/jats:italic>\n , with subsequent confirmation by blood PCR and smear demonstrating <0.01% parasitemia. The patient improved following treatment with atovaquone and azithromycin, along with corticosteroids for HLH.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n This case highlights the heterogeneity of babesiosis and its potential to present with minimal parasitemia, yet severe systemic inflammation in immunocompromised hosts. Additionally, this case underscores the importance of maintaining a broad differential in patients on B cell-depleting agents who present with new pancytopenia and systemic inflammatory symptoms. Early utilization of microbial cell-free DNA next-generation sequencing tests may aid in timely diagnosis and treatment.<\/jats:p>\n <\/jats:sec>\n <\/jats:sec>","DOI":"10.1128\/asmcr.00066-26","type":"journal-article","created":{"date-parts":[[2026,7,24]],"date-time":"2026-07-24T13:00:08Z","timestamp":1784898008000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Babesiosis at ultra-low parasitemia presenting as secondary hemophagocytic lymphohistiocytosis in a patient on B cell-depleting therapy"],"prefix":"10.1128","volume":"2","author":[{"given":"Nadia","family":"Toumeh","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02qp3tb03","id-type":"ROR","asserted-by":"publisher"}],"name":"Division of Hospital Internal Medicine, Mayo Clinic","place":["Rochester, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4329-4515","authenticated-orcid":true,"given":"Bismarck S.","family":"Bisono Garcia","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02qp3tb03","id-type":"ROR","asserted-by":"publisher"}],"name":"Division of Hospital Internal Medicine, Mayo Clinic","place":["Rochester, USA"]},{"id":[{"id":"https:\/\/ror.org\/02qp3tb03","id-type":"ROR","asserted-by":"publisher"}],"name":"Division of Public Health, Infectious Diseases, and Occupational Medicine, Mayo Clinic","place":["Rochester, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Felicity C.","family":"Norrie","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02qp3tb03","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Laboratory Medicine and Pathology, Mayo Clinic","place":["Rochester, 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Clinic","place":["Rochester, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_1_2_2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMra1202018"},{"key":"e_1_3_1_3_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.idcr.2022.e01570"},{"key":"e_1_3_1_4_2","doi-asserted-by":"publisher","DOI":"10.1186\/s12941-017-0179-z"},{"key":"e_1_3_1_5_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.msard.2020.102731"},{"key":"e_1_3_1_6_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.idcr.2025.e02172"},{"key":"e_1_3_1_7_2","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2023.1210041"},{"key":"e_1_3_1_8_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijid.2017.09.026"},{"key":"e_1_3_1_9_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41564-018-0349-6"},{"key":"e_1_3_1_10_2","doi-asserted-by":"publisher","DOI":"10.1186\/s12879-021-06292-4"}],"container-title":["ASM Case 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