Clinical Presentation - Anaphylactic Transfusion Reactions

A severe allergic reaction may begin after infusion of only a few mL with symptoms that may be mild at first but can rapidly progress to loss of consciousness, shock, and, in rare cases, death. Reactions usually occur within 1 to 45 minutes of the start of transfusion, although the less severe anaphylactoid reactions may begin up to 2-3 hours after the transfusion was initiated.

Symptoms are categories by body system in the following table:

Mechanism

IgE-mediated reactions are type I immediate hypersensitivity reactions. IgE has the ability to bind to mast cells and tissue basophils through Fc receptors on their cell membranes. Mast cells (armed with a surface coating of IgE) are triggered when the patient next becomes exposed to the antigen (allergen) recognized by the IgE. This leads to cross-linking of the bound IgE antibody, producing mast cell degranulation with release of preformed and new mediators of the allergic reaction.

Histamine is the most important preformed mediator. It causes vasodilation, increased vascular permeability, increased mucous secretion by nasal and bronchial glands, and smooth muscle contraction. Other granule compounds that mediate the reaction include heparin, enzymes, leukotrienes, cytokines, and activating factors such as the eosinophil and neutrophil chemotactic factors and platelet activating factor.

In the case of class-specific antibodies to IgA, IgA deficiency has a frequency of about 1 in 700 in persons of European descent, defined as less than 0.0005 g/L of IgA. Some of these individuals will have immune or naturally occurring (no history of prior exposure to blood or blood products via pregnancy or transfusion) anti-IgA that is capable of causing anaphylactic reactions.