Irritation to the skin causes the mast cells to release histamine, resulting in the hives you see here.
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Urticaria pigmentosa

Urticaria Pigmentosa is the most common form of cutaneous mastocytosis. It is a rare disease caused by excessive amounts of mast cells in the skin that produce hives or lesions on the skin when irritated. more...

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Prevalence

Urticaria pigmentosa is a orphan disease, affecting fewer than 200 000 people in the United States.

Diagnosis

The disease is most often diagnosed as an infant, when parents take their baby in for what appears to be bug bites. The bug bites are actually the clumps of mast cells. Doctors can confirm the prescence of mast cells by rubbing the baby's skin. If hives appear, it most likely signifies the presence of urticaria pigmentosa.

Symptoms

Urticaria Pigmentosa is characterized by excessive amounts of mast cells in the skin. Red or brown spots are often seen on the skin, typically around the chest and forehead. These mast cells, when irritated (e.g. by rubbing the skin, heat exposure), produce too much histamine, triggering an allergic reaction that leads to hives localized to the area of irritation. Severe itching usually follows, and scratching the area only serves to further symptoms. Symptoms can range from very mild (flushing, hives, no treatment needed) to life-threatening (vascular collapse).

Irritants

The following can worsen the symptoms of Urticaria Pigmentosa:

  1. Emotional Stress
  2. Physical Stimuli such as heat, friction, and excessive exercise
  3. Bacterial toxins
  4. Venom
  5. Eye drops containing dextran
  6. NSAIDs
  7. Alcohol
  8. morphine

The classification of NSAIDs can be disputed. Aspirin, for example, causes the mast cells to degranulate, releasing histamines and causing symptoms to flare. However, daily intake of 81mg aspirin may keep the mast cells degranulated. Thus, while symptoms may be worsened at first, they can get better as the mast cells are unable to recover.

Treatments

There are no cures for Urticaria Pigmentosa. However, treatments are possible. Most treatments for mastocytosis can be used to treat Urticaria Pigmentosa.

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Mastocytosis
From Gale Encyclopedia of Medicine, 4/6/01 by J. Ricker Polsdorfer

Definition

Mastocytosis is a disease characterized by the presence of too many mast cells in various organs and tissues.

Description

The body has a variety of free-roaming cell populations that function as immunogenic agents. Most immunogenic cells fall into the category of white blood cells, but some remain in tissues and are not found in the blood. Mast cells are such a group.

Mast cells are found primarily in the skin and digestive system, including the liver and spleen, and produce histamine, a chemical most famous for its ability to cause itching. Histamine also causes acid indigestion, diarrhea, flushing, heart pounding, headaches, and can even cause the blood pressure to drop suddenly.

Mastocytosis comes in three forms. Most cases produce symptoms but do not shorten life expectancy. The three forms are:

  • Mastocytoma, a benign skin tumor.
  • Urticaria pigmentosa, small collections of mast cells in the skin that manifest as salmon or brown-colored patches.
  • Systemic mastocytosis, the collection of mast cells in the skin, lymph nodes, liver, spleen, gastrointestinal tract, and bones.

Causes & symptoms

The cause of mastocytosis is unknown. People with systemic mastocytosis have bone and joint pain. Peptic ulcers are frequent because of the increased stomach acid stimulated by histamine. Many patients with systemic mastocytosis also develop urticaria pigmentosa. These skin lesions itch when stroked and may become fluid-filled.

Diagnosis

A biopsy of the skin patches aids diagnosis. An elevated level of histamine in the urine or blood is also indicative of mastocytosis.

Treatment

Mastocytoma usually occurs in childhood and clears-up on its own. Urticaria pigmentosa (present alone without systemic disease) also dramatically clears or improves as adolescence approaches.

Several medications are helpful in relieving symptoms of systemic mastocytosis. Antihistamines and drugs that reduce stomach acid are frequently needed. Headaches respond to migraine treatment. A medicine called cromolyn helps with the bowel symptoms. Several other standard and experimental medications have been used.

Prognosis

Mastocytoma and urticaria pigmentosa rarely if ever, develop into systemic mastocytosis, and both spontaneously improve over time. Systemic mastocytosis is only symptomatically treated. There is no known treatment that decreases the number of mast cells within tissue.

Key Terms

Non-steroidal anti-inflammatory drugs (NSAIDs)
Aspirin, ibuprofen, naproxen, and many others.
Peptic ulcer
Ulcers in the stomach and upper duodenum (first portion of the small intestine) caused by stomach acid and a bacterium called .

Further Reading

For Your Information

    Books

  • Austen, K. Frank. "Diseases of immediate type hypersensitivity." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, pp.1866-1867.
  • Metcalfe, Dean D. "Mastocytosis." In Cecil Textbook of Medicine, edited by J. Claude Bennett and Fred Plum. Philadelphia: W. B. Saunders, 1996, pp.1435-1437.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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