Babesia parasitemia rebound after red blood cell exchange

Babesiosis is an increasingly recognized disease which may benefit from therapeutic apheresis (Category II/Grade 2C). Vulnerable populations include the splenectomized, those aged >50, those with malignancies, and the immunocompromised. In the setting of parasite levels > 10%, significant anemia, renal impairment, pulmonary compromise, or hepatic dysfunction, RBC exchange can rapidly reduce parasite burdens and decrease the bioavailability of proinflammatory cytokines. No previous report has shown such a rapid rebound in parasitemia despite adequate organism removal. Herein, we report a case of severe babesiosis in a splenectomized 56 year old male with a past medical history significant for benign multiple sclerosis. Following a week of flu-like symptoms, the patient presented to an outside hospital with anemia, elevated bilirubin, thrombocytopenia, and 15% of his RBCs containing Babesia forms on a peripheral smear. Despite initiation of appropriate antimicrobials, subsequent transfer to our facility revealed worsening parasitemia (25%), tachypnea, and hypoxia. An emergent two volume RBC exchange was performed, resulting in 15% post-exchange parasitemia. Twelve hours later, the parasitic burden had climbed to 30%. A second RBC exchange reduced the parasite burden to 1.5%. His post-procedural course was significant for diminishing periodic increases in parasitemia despite continued antimicrobial therapy. Rapid increases in parasitic burden following RBC exchanges can occur and post-procedural surveillance of parasitemia should be closely monitored to expedite additional exchanges.