Severe Babesia microti infection in an American immunocompetent patient diagnosed in Spain.

We report a severe Babesia microti infection in an immunocompetent patient diagnosed in Spain. A 66-year-old woman coming from USA presented with fever, thrombocytopenia, and multiorgan failure. Intraerythrocytic parasites were observed in Giemsa-stained peripheral blood smears and B. microti was first suspected by optical microscopy and afterward confirmed by specific polymerase chain reaction (PCR). Patient received antibiotic therapy, vital support measures and one red blood cell (RBC) exchange procedure. After 15 days, patient recovered and she was transferred to her reference hospital. This case report highlights the importance of clinical suspicion by physicians in non-endemic areas to diagnose this entity, the differential diagnosis with malaria infection, and the indication of RBC exchange as a therapeutic apheresis modality in the management of severe forms.