Neutrophil-erythrocyte rosettes: a rare morphologic clue to autoimmune hemolytic anemia

A 69-year-old woman with previously treated endometrial carcinoma developed progressive anemia, with hemoglobin declining to 4.2 g/dL and later stabilizing between 6-7 g/dL despite preserved leukocyte and platelet counts. Laboratory evaluation demonstrated elevated erythropoietin, lactate dehydrogenase (LDH), bilirubin, vitamin B12, and iron levels, prompting further investigation. The key diagnostic finding was the presence of neutrophil erythrocyte rosettes on peripheral smear-neutrophils encircled by antibody-coated red cells through Fc-mediated binding. This rare morphologic phenomenon, seldom described in autoimmune hemolytic anemia (AIHA), provided a crucial early clue, especially in the absence of spherocytes or red cell fragments. Reticulocytosis supported ongoing hemolysis, and monospecific direct antiglobulin test (DAT) later confirmed IgG-mediated AIHA. Elevated rheumatoid factor suggested an autoimmune predisposition. Recognition of neutrophil-erythrocyte rosettes in this case directly guided confirmatory testing and diagnosis, emphasizing their diagnostic significance.