Thoendel, Matthew J

ABSTRACT Background Babesia microti , a parasite transmitted by the Ixodes scapularis 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). Case Summary 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 Babesia microti , 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. Conclusion 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.

We previously demonstrated that shotgun metagenomic sequencing can detect bacteria in sonicate fluid, providing a diagnosis of prosthetic joint infection (PJI). A limitation of the approach that we used is that data analysis was time-consuming and specialized bioinformatics expertise was required, both of which are barriers to routine clinical use.

Metagenomic shotgun sequencing has the potential to transform how serious infections are diagnosed by offering universal, culture-free pathogen detection. This may be especially advantageous for microbial diagnosis of prosthetic joint infection (PJI) by synovial fluid analysis since synovial fluid cultures are not universally positive and since synovial fluid is easily obtained preoperatively.