Differential Diagnosis

When considering the symptoms described, the following differential diagnoses can be organized into categories based on their likelihood and potential impact:

• Single most likely diagnosis:

  • Dermatographism: This condition is characterized by the appearance of red, itchy, and raised marks after scratching the skin. It is often seen in response to minor trauma, such as scratching, and can be exacerbated by heat, which aligns with the symptoms described.

• Other Likely diagnoses:

  • Urticaria: Also known as hives, urticaria can cause red, itchy welts that appear after scratching or due to heat. The reaction is usually temporary and can be triggered by various factors, including environmental changes.
  • Keratosis pilaris: This is a harmless condition that causes small, rough patches on the skin, which can sometimes become red and itchy. Scratching these areas might lead to temporary red marks.
  • Dry skin (xerosis): Dry skin can become itchy and, when scratched, may leave red marks due to irritation and inflammation.

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

  • Mastocytosis: A rare condition where mast cells accumulate in the skin and other tissues, leading to symptoms like itching, redness, and hives upon scratching. While rare, it's crucial to consider due to its potential systemic implications.
  • Cutaneous mast cell degranulation disorders: Conditions like mast cell activation syndrome can cause a range of symptoms, including skin reactions to heat or minor trauma, and are important to diagnose due to their potential for severe reactions.

• Rare diagnoses:

  • Ehlers-Danlos syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. Some types can lead to easy bruising and skin hyperextensibility, which might be mistaken for red marks after scratching.
  • Sickle cell disease: In rare cases, sickle cell disease can cause skin manifestations, including painful crises that might be accompanied by redness and itching, though this would typically be part of a broader clinical picture.