Understanding Mastocytosis

by National Institute of Health

Mastocytosis is a disorder in both children and adults. It is caused by the presence of too many mast cells in your body. You can find mast cells in skin, linings of the stomach and intestine, and connective tissue (such as cartilage or tendons). 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 1933. The true incidence of either type of mastocytosis remains unknown, but mastocytosis generally is considered to be an "orphan disease." (Orphan diseases affect approximately 200,000 or fewer people in the United States.)

Symptoms

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 musculoskeletal pain, abdominal discomfort, nausea and vomiting, ulcers, diarrhea, skin lesions.

It can also cause episodes of hypotension (very low blood pressure and faintness) or anaphylaxis (shock).

Diagnosis

Your doctor can diagnose urticaria pigmentosa by the appearance of your skin and confirm it by finding an abnormally high number of mast cells on a skin biopsy. The diagnosis of systemic mastocytosis is made when an increased number of abnormal mast cells is found during an examination of your bone marrow.

Other tests that are important in evaluating a suspected case of mastocytosis include a search for specific genetic mutations that health experts associate with this disease.

Treatment

Doctors use several medicines to treat mastocytosis symptoms, including antihistamines (to prevent the effect of mast cell histamine) and anticholinergics (to relieve intestinal cramping). A number of medicines treat specific symptoms of mastocytosis. Antihistamines frequently treat itching and other skin complaints, Antihistamines that work specifically against ulcers and proton pump inhibitors relieve ulcer-like symptoms. Two types of antihistamines treat severe flushing and low blood pressure before symptoms appear and epinephrine after symptoms begin. Topical steroids temporarily reduce skin lesions that are cosmetically disturbing. Steroids treat malabsorption, or impaired ability to take in nutrients

In cases in which mastocytosis is malignant, cancerous, or associated with a blood disorder, steroids and/or chemotherapy may be necessary.

Research

National Institute of Allergy and Infectious Diseases (NIAID) scientists have studied and treated patients with mastocytosis for more than two decades at the National Institutes of Health (NIH) Clinical Center.

Scientists also are focusing on identifying disease-associated gene mutations. Several such mutations have been identified at NIH in a receptor for a mast cell growth factor. Understanding such mutations help researchers to understand the causes of mastocytosis, improve diagnosis, and lead to better treatment methods.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.