Urticaria pigmentosa

Urticaria pigmentosa

Chris Schach

Author Bio -

 Key points
* Condition is a type of mastocytosis resulting in brown patches appear on the skin, causing itching, swelling and redness.
* In children, the patches appear over the first few months, persisting and increasing in number, but often disappearing in adolescence.
* In adults, the patches tend to persist in the long term.
* Certain medications can exacerbate the Urticaria pigmentosa.

Urticaria pigmentosa is a type of mastocytosis, in which brown patches appear on the skin due to an abnormal collection of mast cells. Mast cells contain granules which contain histamine and other chemicals. When the mast cell gets disturbed, they release these chemicals into the surrounding skin. The chemicals cause leaky blood vessels, resulting in itching, swelling, and redness.

In children, urticaria pigmentosa most often affects infants in the first few months. Often, the patches are confused with insect bites, but persist and increase in number over the next few months or years. They can appear on any part of the body including scalp, face, trunk, and limbs. In young children, the patches blister when rubbed. If several patches are rubbed at the same time, the infant may become irritable but it is uncommon for severe symptoms to arise. Over the next few years, the urticaria pigmentosa becomes less irritable and eventually the patches fade. By the teenage years, most patches will have gone.

Sometimes urticaria pigmentosa develops for the first time in adulthood. Few or many patches can appear and be unsightly as well as itchy. For adults, urticaria pigmentosa tends to persist in the long term. It can also cause internal symptoms. Telangiectasia eruptiva macularis perstans (TEMP) is a rare form of mastocytosis in which diffuse red patches occur associated with overlying telangiectasia (dilated capillaries).

Accumulation of mast cells in other organs as well as the skin is known as systemic mastocytosis. Affected sites may be bone, liver, spleen, lymph nodes or the gastrointestinal tract. Systemic mastocytosis may cause fever, weight loss, diarrhea and abdominal pain. Rarely, systemic mastocytosis is due to malignancy (cancer) and results in mast cell leukemia.

Exercise or heat can aggravate symptoms. A severe reaction can result in flushing and faintness. Certain medications should be avoided if there is extensive Urticaria pigmentosa such as aspirin and other nonsteroidal anti-inflammatory drugs, codeine and morphine, alcohol, and anticholinergics.

Differential Diagnosis (Other conditions with similar appearance)
Amyloidosis, Macular
Epidermolysis bullosa
Herpes simplex
Linear IgA dermatosis

    Key Points
    * The patches are so characteristic no specific tests are necessary.
    * A skin biopsy or other tests can determine complications from internal involvement.
    * A Darier sign can be determined by rubbing one of the brown patches causing redness, swelling, and itching.

    The brown patches of urticaria pigmentosa are so characteristic that no specific tests are necessary. However, a skin biopsy can confirm the diagnosis. If there are symptoms suggesting internal involvement, the following tests may be helpful — x-rays to show bone thinning, liver function blood tests which may be normal even with liver involvement, and urinary histamine levels or 1,4-methylimidazole acetic acid levels of elevation.
    One can demonstrate the presence of mast cells by rubbing one of the brown patches. Within a few minutes, the rubbed area becomes reddened, swollen and itchy. This is known as Darier sign, and confirms the presence of Mastocytosis.

    *Condition is not serious and does not require treatment.
    * There are medications and treatments that can be helpful.

    Urticaria pigmentosa is not serious, and does not require any treatment in most cases. The following treatments can be helpful: oral antihistamines, mast cell stabilisers including disodium cromoglicate, low-dose aspirin (which maybe worse symptoms in some patients), topical steroids (can reduce itching but the patches tend to recur), PUVA (Photochemotherapy) — the most effective in adults even with recurring patches in 6-12 months, interferon, and imatinib (Gleevec).

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