Differential Diagnosis for 58-year-old Female with Hives
Single Most Likely Diagnosis
- Allergic reaction to amoxicillin: The patient's recent initiation of amoxicillin for a sore throat, coupled with the onset of hives, strongly suggests an allergic reaction to the medication. The annular shape of the hives over extensor surfaces is consistent with an allergic etiology.
Other Likely Diagnoses
- Urticarial vasculitis: This condition involves inflammation of the blood vessels and can present with hives, often on the extensor surfaces. It may be related to the patient's recent infection or medication use.
- Autoimmune urticaria: This condition involves the immune system attacking the body's own tissues, leading to hives. It can be triggered by infections or medications.
- Infection-related urticaria: The patient's recent sore throat and amoxicillin use may be contributing to an infection-related urticaria, although this is less likely given the temporal relationship with medication initiation.
Do Not Miss Diagnoses
- Stevens-Johnson syndrome (SJS) or Toxic Epidermal Necrolysis (TEN): Although rare, these conditions are life-threatening and can be triggered by medications like amoxicillin. They present with skin lesions, including hives, and can progress to widespread skin necrosis.
- Anaphylaxis: A severe, life-threatening allergic reaction that can present with hives, among other symptoms. Although the patient's symptoms are currently limited to hives, anaphylaxis is a potential complication of an allergic reaction.
Rare Diagnoses
- Erythema multiforme: A rare skin condition characterized by target-shaped lesions, which can be triggered by infections or medications.
- Mastocytosis: A rare condition involving the accumulation of mast cells in the skin, which can present with hives and other skin lesions.
- Paraneoplastic urticaria: A rare condition in which urticaria is associated with an underlying malignancy.