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Mastocytosis is a disorder that can occur in both children and adults. It is caused by the presence of too many mast cells in your body.
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You can find mast cells in skin, lymph nodes, internal organs (such as the liver and spleen) and the linings of the lung, stomach, and intestine. Mast cells play an important role in helping your immune system defend these tissues from disease. Mast cells attract other key players of the immune defense system to areas of your body where they are needed by releasing chemical “alarms” such as histamine and cytokines.
Mast cells seem to have other roles as well. Found to gather around wounds, they may play a part in wound healing. For example, the typical itching you feel around a healing scab may be caused by histamine released by mast cells. Researchers also think mast cells may have a role in the growth of blood vessels. No one with too few or no mast cells has ever been found. This fact indicates to some scientists that having too few mast cells may be incompatible with life.
The presence of too many mast cells, or mastocytosis, can occur in two forms—cutaneous and systemic. The most common cutaneous (skin) form is also called urticaria pigmentosa, which occurs when mast cells infiltrate the skin. Systemic mastocytosis is caused by mast cells accumulating in the tissues and can affect organs such as the liver, spleen, bone marrow, and small intestine.
Researchers first described urticaria pigmentosa in 1869. Systemic mastocytosis was first reported in the scientific literature in 1949. The true number of cases of either type of mastocytosis remains unknown, but mastocytosis generally is considered to be an “orphan disease.” (Orphan diseases affect about 200,000 or fewer people in the United States.)
Chemicals released by mast cells cause changes in your body’s functioning that lead to typical allergic responses such as flushing, itching, abdominal cramping, and even shock. When too many mast cells are in your body, the additional chemicals can cause
It can also cause episodes of hypotension (very low blood pressure and faintness) or anaphylaxis (shock).
Your healthcare provider can diagnose cutaneous mastocytosis by the appearance of your skin and confirm it by finding an abnormally high number of mast cells on a skin biopsy. Your provider can diagnose systemic mastocytosis by finding an increased number of abnormal mast cells during an examination of your bone marrow.
Other tests that are important in evaluating a suspected case of mastocytosis include:
Healthcare providers use several medicines to treat mastocytosis symptoms, including antihistamines (to prevent the effect of mast cell histamine—a chemical) and anticholinergics (to relieve intestinal cramping). A number of medicines treat specific symptoms of mastocytosis.
In cases in which mastocytosis is malignant, cancerous, or associated with a blood disorder, steroids and/or chemotherapy may be necessary.
NIAID scientists have studied and treated patients with mastocytosis for more than three decades at the National Institutes of Health (NIH) Clinical Center.
Some of the most important research advances for this rare disorder include
For example, researchers have developed drugs that help block the division of mast cells and the action of chemicals released from mast cells.
Scientists also are focusing on identifying gene mutations associated with the disease. Several such mutations have been identified at NIH in a cell receptor for a mast cell growth factor and in key molecules within mast cells that control cell activation. Understanding such mutations helps researchers understand the causes of mastocytosis, improve diagnosis, and develop better treatment.
Mastocytosis fact sheet (PDF)
NIH Office of Rare Diseases Research, Genetic and Rare Diseases Information Center
National Library of Medicine, MedlinePlus
The Mastocytosis Society, Inc.
National Organization for Rare Disorders
Last Updated October 28, 2013
Last Reviewed October 28, 2013