Anaphylaxis and coagulopathy: from rare case reports to mechanistic insights.

Anaphylaxis is an unpredictable hypersensitivity reaction characterized by acute, life-threatening cardiopulmonary dysfunction, including shock, angioedema, and bronchospasm. Although coagulopathy and disseminated intravascular coagulation (DIC) have been reported in association with anaphylaxis, they remain uncommon manifestations. Based on limited case reports, proposed mechanisms of anaphylaxis-associated coagulopathy include the release of mast cell-derived mediators such as tryptase, platelet-activating factor, and heparin, as well as activation of the contact system. DIC may result from systemic coagulopathy as a consequence of the physiologic effects of shock, including ischemic hepatitis ("shock liver"). DIC is a pathological state due to a secondary cause and is diagnosed based on laboratory findings such as prolonged prothrombin time, thrombocytopenia, and elevated D-dimer and low fibrinogen levels. Recent systematic review data suggest an approximate 50% mortality in reported cases of anaphylaxis-associated DIC; while bleeding is the predominant clinical manifestation, thrombotic complications account for most fatal outcomes. This review examines the available clinical and mechanistic evidence for anaphylaxis-associated coagulopathy, explores diagnostic challenges, and highlights implications for patient management.