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Urticaria pigmentosa

  • Definition
    • Urticaria pigmentosa is a skin disease that produces patches of darker skin (lesions) and very bad itching. Hives can develop when these skin areas are rubbed. 

  • Alternative Names
    • Mastocytosis; Mastocytoma

  • Causes
    • Urticaria pigmentosa occurs when there are too many inflammatory cells (mast cells) in the skin.

      Urticaria pigmentosa is most common in children. It can also occur in adults.

  • Symptoms
    • The main symptom is brownish patches on the skin. Rubbing the skin sore causes hive-like bumps. Younger children may develop a blister that is filled with fluid if the bump is scratched.

      The face may also get red quickly.

      In severe cases, these symptoms may occur:

      • Diarrhea
      • Fainting (uncommon)
      • Headache
      • Rapid heartbeat 
  • Exams and Tests
    • Tests to check for this condition are:

      • Skin biopsy to look for a higher number of mast cells
      • Urine histamine (histamines are chemicals your body produces as a response to some conditions) 
      • Blood tests for blood cell counts and blood tryptase levels (tryptase is an enzyme found in mast cells)
  • Treatment
    • Antihistamine medicines can help relieve symptoms such as itching and flushing. Talk to your health care provider about which type of antihistamine to use.

      Your provider may prescribe other kinds of medicine to treat symptoms of severe and unusual forms of urticaria pigmentosa.

  • Outlook (Prognosis)
    • Urticaria pigmentosa goes away by puberty in about half of affected children. Symptoms usually get better in others as they grow into adulthood.

      In adults, urticaria pigmentosa can lead to systemic mastocytosis. This is a serious condition that can affect bones, the brain, nerves, and the digestive system.

  • Possible Complications
    • The main problems are discomfort from itching and concern about the appearance of the spots. Other problems such as diarrhea and fainting are rare.

      Certain medicines may trigger flares of urticaria pigmentosa. Discuss these with your health care provider.

      Bee stings may also cause a bad allergic reaction in people with urticaria pigmentosa. Ask your provider if you should carry an epinephrine kit to use if you get a bee sting.

  • When to Contact a Medical Professional
    • Call your health care provider if you notice symptoms of urticaria pigmentosa.

  • References
    • Habif TP. Urticaria and angioedema. In: Habif TP, ed. Clinical Dermatology. 5th ed. St. Louis, MO: Elsevier Mosby; 2009:chap 6.

      Tharp MD. Mastocytosis. In: Bolognia JL, Jorizzo JL, Schaffer JV, et al, eds. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Mosby; 2012:chap 118.