Mastocytosis

Mastocytosis is a group of disorders of both children and adults caused by the presence of too many mast cells in a person's body. Located in connective tissue, including the skin, the linings of the stomach and intestine, and other sites, mast cells may play an important role in helping defend these tissues from disease. By releasing chemical "alarms" such as histamine[?], mast cells attract other key players of the immune defense system to areas of the body where they are needed.

Mast cells seem to have other roles as well. Because they gather together around wounds, mast cells 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 been found, which indicates to some scientists that we may not be able to survive with too few mast cells.

The presence of too many mast cells, or mastocytosis, can occur in two forms - cutaneous (skin) and systemic (involves internal body organs). Cutaneous mastocytosis (CM), the most common form, occurs when mast cells increase in the skin. It is also called urticaria pigmentosa. CM mostly affects children.

Systemic mastocytosis is caused when mast cells collect in the tissues and can affect organs such as the liver, spleen, lymph nodes, and bone marrow.

Scientists first described urticaria pigmentosa in 1869. Systemic mastocytosis was first reported by scientists in 1936. No one is sure how many people have either type of mastocytosis, but mastocytosis generally has been considered to be an "orphan disease[?]." (Orphan diseases affect 200,000 or fewer people in the United States.) Mastocytosis, however, often may be misdiagnosed, and occur more frequently than assumed.

Table of contents 1 Symptoms 2 Diagnosis 3 Treatment 4 Research

Symptoms

Chemicals released by mast cells cause changes in the immune system leading to typical allergy symptoms such as itching, abdominal cramping, and even anaphylaxis (dangerously low blood pressure).

When too many mast cells exist in a person's body, the additional chemicals can cause

• Bone or muscle pain
• Abdominal discomfort
• Nausea and vomiting
• Stomach ulcers
• Diarrhea
• Skin lesions
• Episodes of very low blood pressure and faintness
• Shock

Diagnosis

Doctors can diagnose urticaria pigmentosa by seeing the characteristic lesions which are dark-brown and fixed. A small skin sample (biopsy[?]) may help confirm the diagnosis.

By taking a tiny piece of tissue from a different organ, such as the bone marrow, the doctor can diagnose systemic mastocytosis. Using special techniques on a bone marrow sample, the doctor looks for an increase in mast cells. Another sign of this disorder is high levels of certain mast-cell chemicals and proteins in a person's blood and sometimes in the urine.

Treatment

Several medicines help treat the symptoms of mastocytosis.

• Antihistamines to work against mast cell chemicals
• Medicines to relieve cramping in the intestines

Medicines help treat other signs and symptoms of mastocytosis, including

• Itching and other skin reactions
• Ulcer-like symptoms
• Low blood pressure
• Inability to take up nutrients from food (malabsorption[?])

In rare cases in which mastocytosis is cancerous or associated with a blood disorder, the patient may have to use steroids and/or chemotherapy.

Research

National Institute of Allergy and Infectious Diseases[?] (NIAID) scientists have been studying and treating patients with mastocytosis for several years at the National Institutes of Health (NIH) Clinical Center.

Some of the most important research advances for this rare disorder include improved diagnosis of mast cell disease and identification of growth factors and genetic mechanisms responsible for increased mast cell production. Researchers are currently evaluating approaches to improve ways to treat mastocytosis.

Scientists also are focusing on identifying disease-associated mutations (changes in genes). NIH scientists have identified some mutations, which may help researchers understand the causes of mastocytosis, improve diagnosis, and develop better treatments.

For more information National Institute of Allergy and Infectious Diseases Building 31, Room 7A50, MSC 2520 31 Center Drive Bethesda, MD 20892-2520 http://www.niaid.nih.gov

U.S. National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894 301-496-6308 http://medlineplus.gov

National Organization for Rare Disorders P.O. Box 8923 New Fairfield, CT 06812-8923 203-746-6518 http://www.rarediseases.org

Mastocytosis Society, Inc. 433 East 300 South Spanish Fork, UT 84660 801-798-2032 http://www.mastocytosis.com

NIAID is a component of the National Institutes of Health (NIH). NIAID supports basic and applied research to prevent, diagnose, and treat infectious and immune-mediated illnesses, including HIV/AIDS and other sexually transmitted diseases, illness from potential agents of bioterrorism, tuberculosis, malaria, autoimmune disorders, asthma and allergies.

---

Press releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at http://www.niaid.nih.gov.

Prepared by: Office of Communications and Public Liaison National Institute of Allergy and Infectious Diseases National Institutes of Health Bethesda, MD 20892

U.S. Department of Health and Human Services