Neoehrlichiosis Causing Hemolytic Anemia in Patients Treated with Rituximab, Norway, 2024-2025

Neoehrlichiosis is caused by infection with the tickborne intracellular bacterium Neoehrlichia mikurensis. We describe 3 cases of direct antiglobulin test-negative hemolytic anemia in rituximab-treated patients infected with tickborne N. mikurensis bacteria in Norway during 2024-2025. All 3 patients had splenomegaly and night sweats. The hemolysis ranged from mild with compensated hemolysis to severe transfusion-dependent hemolysis that resulted in splenectomy in 1 case. All patients experienced complete resolution of hemolytic anemia and other symptoms of infection after eradication therapy with doxycycline for 21 days. Neoehrlichiosis should be considered as a curable cause of hemolytic anemia in N. mikurensis-endemic regions.