Differential Diagnosis for Hives, Syncope, a few hours after IV Iron Infusion

• Single most likely diagnosis:

  • Anaphylactic reaction to IV iron: This is the most likely diagnosis given the symptoms of hives and syncope occurring shortly after the infusion. Anaphylaxis is a severe, life-threatening allergic reaction that can occur within minutes of exposure to an allergen, in this case, the IV iron.

• Other Likely diagnoses:

  • Hypotensive reaction to IV iron: While not as severe as anaphylaxis, some patients may experience a significant drop in blood pressure due to the infusion, leading to syncope. Hives could be part of a less severe allergic reaction.
  • Allergic reaction (non-anaphylactic): A less severe allergic reaction could cause hives without the full spectrum of anaphylaxis symptoms, but still potentially leading to syncope due to anxiety or other factors.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):

  • Septic shock: Although less likely, if the IV iron infusion became contaminated, it could lead to a severe infection. The initial symptoms might mimic an allergic reaction, making it crucial not to miss this potentially fatal condition.
  • Cardiac event: The stress of an allergic reaction or the infusion itself could potentially trigger a cardiac event in susceptible individuals, which would be critical to identify and treat promptly.

• Rare diagnoses:

  • Iron overload reaction: While rare, an acute reaction to iron overload could potentially cause systemic symptoms, though this would be more expected in cases of significant iron overdose rather than a standard infusion.
  • Mastocytosis or mast cell activation syndrome: These conditions involve the accumulation of mast cells or their abnormal activation, which could lead to anaphylaxis-like symptoms in response to various triggers, including possibly IV iron. However, these are rare conditions and would not typically be the first consideration without other supporting evidence.