Differential Diagnosis for General Pruritis and Upper Lip Angioedema

• Single Most Likely Diagnosis
  • Angiotensin-Converting Enzyme (ACE) Inhibitor-Induced Angioedema: The patient has been on ACE inhibitors for years, which is a well-known cause of angioedema, especially in the absence of other identifiable allergens. The onset can be delayed, and it does not necessarily require a new exposure to the drug.
• Other Likely Diagnoses
  • Allergic Reaction: Despite no known exposure to an allergen, an allergic reaction to an unknown substance cannot be ruled out. This could be due to a new food, medication (other than ACEi), or environmental exposure.
  • Urticarial Vasculitis: This condition presents with skin lesions that can resemble urticaria but are due to inflammation of the blood vessels. It can cause pruritis and angioedema-like symptoms.
• Do Not Miss Diagnoses
  • Hereditary Angioedema (HAE): Although less common, HAE can present at any age and is crucial to diagnose due to its potential for severe, life-threatening episodes. A family history may or may not be present.
  • Anaphylaxis: While the presentation might not fully align with anaphylaxis (given the lack of respiratory or cardiovascular symptoms), any condition that could potentially progress to anaphylaxis should be considered, especially if the patient's condition worsens.
• Rare Diagnoses
  • Acquired Angioedema: This can be due to lymphoproliferative disorders, autoimmune diseases, or infections, which might not be immediately apparent but could explain the symptoms if other causes are ruled out.
  • Erythema Multiforme or Stevens-Johnson Syndrome: Although these conditions typically present with more specific skin lesions, they can cause significant morbidity and should be considered in the differential diagnosis of any patient with new-onset skin symptoms and angioedema.