Definition of Urticaria pigmentosa:

Urticaria pigmentosa is a skin disease that produces lesions and intense itching. If you rub the lesions, hives may develop.

Causes, incidence, and risk factors:

Urticaria pigmentosa is one of several forms of mastocytosis, which occurs where there are too many inflammatory cells (mast cells) in the skin.

Urticaria pigmentosa is most often seen in children, but it can also occur in adults.

Symptoms:

The main symptom is brownish lesions on skin. Rubbing the skin sore causes a hive-like bump. Younger children may develop a fluid-filled blister if it is scratched.

The face may also become flushed.

In severe cases, the following symptoms may occur:

• Diarrhea
• Fainting (uncommon)
• Headache
• Rapid heartbeat (tachycardia)

Signs and tests:

• Skin biopsy to confirm an increase in the number of mast cells
• Urine histamine

Treatment:

Antihistamines may relieve symptoms such as itching and flushing. Discuss the choice of antihistamine with your child's health care provider. Other medications may be recommended for symptoms of more severe and unusual forms of urticaria pigmentosa.

Expectations (prognosis):

Urticaria pigmentosa goes away by puberty in about half of the affected children. Symptoms usually get better in others as they grow into adulthood.

In adults, urticaria pigmentosa may develop into a more serious condition called systemic mastocytosis.

Complications:

Discomfort from itching, and possible self-consciousness about the "spots," are the primary complications. Other problems such as diarrhea and fainting are rare.

Certain medications may trigger flares of urticaria pigmentosa. Discuss these with your doctor.

Bee stings may also cause severe allergic reactions in some patients with urticaria pigmentosa. Your doctor may advise you to carry an injectable epinephrine kit (such as EpiPen or Twinject) to be used in case of a bee sting.

Calling your health care provider:

Call for an appointment with your health care provider if your child has symptoms of urticaria pigmentosa.