Urticaria pigmentosa

Alternative names:

mastocytoma; mastocytosis; systemic mastocytosis

Definition:

A disease that produces skin lesions, intense itching, and hive formation at the site of the lesion upon rubbing.

Causes, incidence, and risk factors:

The cause of urticaria pigmentosa is unknown. Affected children develop skin lesions by age 2. These lesions may be tan to light brown in color and contain mast cells that produce histamine. Histamine is responsible for the typical skin response and may be responsible for systemic symptoms. Rubbing of a lesion produces a rapid wheal (a hive-like bump). Younger children may develop a fluid-filled blister over a lesion if it is traumatized.

A large histamine release may cause flushing, headache, diarrhea, a rapid heartbeat (tachycardia), and even fainting. This is uncommon with urticaria pigmentosa but may be seen in other forms of mastocytosis.

Urticaria pigmentosa is one of several forms of mastocytosis. Other forms include the solitary mastocytoma (a single lesion) and systemic mastocytosis (involvement in organs other than the skin).

Urticaria pigmentosa often disappears by puberty. It is considered a self-limiting benign disease.