Febrile Nonhemolytic Transfusion Reaction

Febrile Nonhemolytic Transfusion Reaction is a common complication that can occur during or shortly after a blood transfusion. It primarily affects the immune system and causes a sudden rise in body temperature or fever. This reaction happens because the body reacts to proteins or white blood cells in the transfused blood. Symptoms often include chills, fever, and sometimes mild discomfort or headache. Although it can be alarming, this reaction does not usually cause serious harm and is different from more severe transfusion reactions. The condition involves the body's immune response to foreign substances in the transfused blood, leading to inflammation and fever.

Febrile Nonhemolytic Transfusion Reaction (FNHTR) is defined as a febrile response occurring during or within 4 hours after a blood transfusion, characterized by an increase in body temperature of at least 1°C (1.8°F) above baseline without evidence of hemolysis. The core pathology involves the recipient's immune system reacting to donor leukocyte-derived cytokines or recipient antibodies against donor human leukocyte antigens (HLA) or white blood cells. FNHTR is the most common type of transfusion reaction and is usually caused by the accumulation of proinflammatory cytokines in stored blood products or alloimmunization to donor leukocytes. Clinically, it presents with fever, chills, and sometimes mild rigors, but without signs of hemolysis or severe allergic reactions. It is important to distinguish FNHTR from more severe transfusion reactions such as acute hemolytic transfusion reaction or transfusion-related acute lung injury (TRALI). FNHTR is significant because it can cause patient discomfort and may lead to unnecessary diagnostic workup if not recognized.