It is a benign occurrence with symptoms that include fever but not directly related with hemolysis.
[1] It is caused by cytokine release from leukocytes within the donor product as a consequence of white blood cell breakdown.
[7] Fever must be at least 38 °C/100.4 °F oral and a change of at least 1 °C/1.8 °F from pre-transfusion value OR chills and/or rigors must be present.
[9] Fever of at least 39 °C, OR a rise in temperature of at least 2 °C from pre-transfusion values AND/OR other symptoms or signs, including chills (rigors), painful muscles (myalgia), or nausea that are severe enough that the transfusion is stopped.
[9] Fever of at least 39 °C, OR a rise in temperature of at least 2 °C from pre-transfusion values AND/OR other symptoms or signs, including chills (rigors), painful muscles (myalgia), or nausea that are severe enough that the transfusion is stopped AND requires immediate medical treatment, admission to hospital, or lengthens the duration of hospital admission.