Urticaria pigmentosa

Urticaria pigmentosa (UP) is a form of cutaneous mastocytosis characterized by brownish or reddish patches on the skin. It is the most common form of mastocytosis, a group of rare disorders caused by an excessive number of mast cells in the body.

Symptoms

The primary symptom of urticaria pigmentosa is the presence of small, round or oval, reddish-brown spots on the skin. These spots, or lesions, can appear anywhere on the body but are most commonly found on the trunk and limbs. When rubbed, the lesions may produce a reaction known as Darier's sign, which involves the formation of a wheal and flare reaction, similar to that seen in urticaria (hives).

Other symptoms can include flushing, itching, abdominal pain, nausea, vomiting, diarrhea, headache, and anaphylaxis in severe cases. These symptoms are caused by the release of histamine and other chemicals from mast cells.

Causes

Urticaria pigmentosa is caused by an excessive number of mast cells in the skin. The exact cause of this increase is unknown, but it is thought to be due to a mutation in the KIT gene, which is involved in the growth and development of mast cells.

Diagnosis

The diagnosis of urticaria pigmentosa is usually made based on the characteristic skin lesions and the presence of Darier's sign. Additional tests may include a skin biopsy, blood tests, and bone marrow biopsy to assess the number of mast cells in the body.

Treatment

Treatment for urticaria pigmentosa is primarily aimed at managing symptoms. This may include the use of antihistamines to reduce itching and flushing, and corticosteroids to reduce inflammation. In severe cases, medications to reduce the number of mast cells may be used.

Prognosis

The prognosis for individuals with urticaria pigmentosa is generally good, although the condition can cause significant discomfort and impact quality of life. In rare cases, urticaria pigmentosa can progress to systemic mastocytosis, a more serious condition that affects multiple organs in the body.

See also

• Mastocytosis
• Cutaneous mastocytosis
• Systemic mastocytosis

Urticaria pigmentosa Resources
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