BACKGROUND: Human granulocytic anaplasmosis (HGA) is a tick-borne rickettsial infectious disease. To date four cases of transfusion-transmitted anaplasmosis (TTA) have been described in the literature, and only one from leukoreduced red blood cells (RBCs).

CASE REPORT: A 64-year-old patient with acute gastrointestinal blood loss was admitted to the hospital and received 5 units of prestorage leukoreduced RBCs. He was stabilized and discharged. He developed headache, fever, and chills 2 days after discharge and was readmitted. On Day 5 of his second admission polymorphonuclear leukocytes containing morulae consistent with HGA were reported in the peripheral smear.

RESULTS: Samples from the recipient tested positive by polymerase chain reaction (PCR) for Anaplasma phagocytophilum, the causative agent of HGA and a segment from one of the five donors tested positive by both serology and PCR.

CONCLUSION: Leukoreduction theoretically reduces the risk of TTA but does not interdict all infections. TTA requires consideration in recipients of RBC transfusion with unexplained fever.