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Understanding blood transfusion reactions is crucial for the USMLE Step 1. Here’s a structured breakdown of key reactions, their pathogenesis, timing, clinical presentation, and immune involvement.
Reaction Type | Pathogenesis | Timing | Clinical Presentation | Donor Factors | Host Factors |
---|---|---|---|---|---|
Allergic/Anaphylactic | Type I hypersensitivity reaction to plasma proteins (e.g., IgA in IgA-deficient patients). | Within minutes to 2–3 hrs | Urticaria, pruritus, wheezing, hypotension, shock. | Donor plasma proteins (e.g., IgA) | Host IgE antibodies against IgA. |
Acute Hemolytic | Type II hypersensitivity due to ABO mismatch; intravascular/extravascular hemolysis. | During transfusion or <24 hrs | Fever, flank pain, hemoglobinuria, jaundice, hypotension. | Donor RBC antigens (A/B groups) | Host IgG/IgM antibodies (anti-A/B). |
Febrile Non-Hemolytic | Cytokines from donor WBCs; mitigated by leukoreduction. | Within 1–6 hrs | Fever, headache, chills, flushing. | Donor WBC cytokines | Host anti-HLA/leukocyte IgG. |
Transfusion-Related Acute Lung Injury (TRALI) | Two-hit mechanism involving neutrophil activation and inflammatory mediators. | Within minutes to 6 hrs | Respiratory distress, non-cardiogenic pulmonary edema. | Donor antileukocyte antibodies | Host neutrophils. |
Delayed Hemolytic | Anamnestic response to donor RBC antigens (e.g., Rh/minor groups); extravascular hemolysis. | >24 hrs (1–2 weeks) | Mild fever, hyperbilirubinemia; usually self-limited. | Donor RBC antigens | Host IgG antibodies. |