Profound Hemolytic Anemia in Babesiosis With Lyme Disease Coinfection and Occult Strongyloidiasis.

Babesiosis is a tick-borne infection caused by intraerythrocytic Babesia parasites and may result in severe hemolytic anemia and systemic complications. Coinfection with other Ixodes-borne pathogens may further complicate diagnosis and management. We report a 45-year-old immunocompetent man working as a landscaper in Connecticut who presented with syncope following two weeks of fever, fatigue, diaphoresis, arthralgias, jaundice, and dark urine. Laboratory evaluation revealed profound hemolytic anemia with a hemoglobin of 6.8 g/dL, elevated lactate dehydrogenase (LDH), undetectable haptoglobin, reticulocytosis, and stage 1 acute kidney injury. Peripheral blood smear demonstrated characteristic Maltese cross formations, with approximately 0.6% parasitemia, and polymerase chain reaction (PCR) testing confirmed Babesia microti and Borrelia burgdorferi coinfection. Direct antiglobulin testing for immunoglobulin G (IgG) was negative. The patient required intensive care monitoring and transfusion and improved following treatment with atovaquone, azithromycin, and doxycycline. Subsequent outpatient evaluation identified asymptomatic Strongyloides stercoralis infection, which was treated with ivermectin. This finding was clinically significant because warm autoimmune hemolytic anemia is a recognized complication of babesiosis and may require corticosteroid therapy, which can precipitate potentially life-threatening Strongyloides hyperinfection in patients with occult infection. This case highlights that severe babesiosis may occur despite low-level parasitemia and emphasizes the importance of recognizing coinfections and obtaining a detailed occupational and environmental exposure history, particularly when future immunosuppressive therapy may be considered.