Case Report: Diagnosis of Hemolytic Anemia from Babesia and Secondary Multi-Pathogen Pneumonia Using a Metagenomic Next-Generation Sequencing Approach.

Babesiosis, as a vector-borne infectious disease, remains relatively rare and is prone to being overlooked and misdiagnosed. Therefore, understanding the epidemiological characteristics and clinical manifestations of babesiosis is crucial for the prompt detection and treatment of the disease. We reported a 63-year-old male patient presenting with spontaneous fever and chills. Laboratory investigations revealed erythrocytopenia, reduced hemoglobin levels, and increased reticulocytes and total bilirubin. Bone marrow examination indicated vigorous cell proliferation, a decreased granulocyte to red cell ratio, and predominant erythroid cell proliferation, with a higher prevalence of intermediate and late-stage juvenile granulocyte and erythroid cells. Initial treatment focused on hemophagocytic syndrome triggered by Epstein-Barr virus infection yielded unsatisfactory results, leading to secondary multiple pulmonary infections. Metagenomic next-generation sequencing (mNGS) of sputum samples pointed to hemolytic anemia induced by Babesia infection, which was subsequently confirmed through peripheral blood smear analysis. The patient responded well to prompt administration of atovaquone and azithromycin, with symptoms resolving and laboratory parameters normalizing. Hemolytic anemia resulting from babesiosis should be distinguished from hemophagocytic syndrome caused by Epstein-Barr virus and other hematologic conditions. mNGS represents an efficient technique for Babesia detection.