Differential Diagnosis for Welts on Skin after Scratches

The patient's symptoms of developing welts on the skin after getting scratches can be approached by considering several potential diagnoses, categorized for clarity and urgency.

• Single Most Likely Diagnosis

  • Dermatographism: This condition is characterized by the appearance of welts or hives after the skin is scratched, rubbed, or subjected to pressure. It's a common and benign condition that aligns closely with the patient's symptoms.

• Other Likely Diagnoses

  • Urticaria: This is a condition marked by the appearance of itchy hives, which can be triggered by various factors, including allergic reactions, infections, or autoimmunity. Scratches could potentially trigger or exacerbate urticaria in susceptible individuals.
  • Allergic Contact Dermatitis: While this condition typically presents with a delayed reaction to allergens coming into contact with the skin, some individuals might experience an immediate reaction that could resemble welts after a scratch if the scratch introduces an allergen into the skin.

• Do Not Miss Diagnoses

  • Mastocytosis: A condition where there's an accumulation of mast cells in one or more organs, including the skin. It can lead to severe allergic reactions, including anaphylaxis, and skin manifestations can include urticaria-like symptoms or dermatographism. Although less common, missing this diagnosis could have significant implications.
  • Angioedema: This condition involves deeper layers of the skin and can cause significant swelling, often in response to an allergic reaction. It's crucial to differentiate it from other causes of welts, especially if there's any involvement of the airways.

• Rare Diagnoses

  • Cold Urticaria: A rare condition where hives or welts develop in response to cold temperatures. While less likely to be directly related to scratches, if the patient experiences symptoms after cold-induced scratches, this could be considered.
  • Solar Urticaria: Another rare condition where exposure to sunlight triggers the appearance of hives. If the patient's symptoms are exacerbated by sunlight after scratches, this could be a rare but possible diagnosis.

Each of these diagnoses has a different set of implications for treatment and management, emphasizing the importance of a thorough diagnostic evaluation to determine the underlying cause of the patient's symptoms.