National Organization for Rare Disorders, Inc.


It is possible that the main title of the report Mastocytosis is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • Systemic Mast Cell Disease
  • Systemic Mastocytosis

Disorder Subdivisions

  • Mast Cell Leukemia
  • Cutaneous Mastocytosis
  • Indolent Systemic Mastocytosis
  • Mastocytosis with an Associated Hematological Disorder
  • Mast Cell Sarcoma/Extracutaneous Mastocytoma
  • Aggressive Systemic Mastocytosis
  • uticaria pigmentosa

General Discussion

Mastocytosis is a rare disorder characterized by abnormal accumulations of mast cells in skin, bone marrow, and internal organs such as the liver, spleen and lymph nodes. Cases beginning during adulthood tend to involve the inner organs in addition to the skin whereas, during childhood, the condition is often marked by skin manifestations with minimal or no organ involvement. When there is evidence of bone marrow or internal organ involvement, the disease is referred to as "systemic mastocytosis".

Although the majority of cases follow an indolent course, some patients may have evidence of a blood disorder such as a myelodysplastic or myeloproliferative disorder at the time of diagnosis. The course and prognosis of mastocytosis in these patients are determined by this associated hematologic disorder. More aggressive forms of mastocytosis and mast cell leukemias are very rarely encountered.


Skin is the most common site of involvement. Urticaria pigmentosa lesions are small, brownish, flat or elevated spots that may be surrounded by reddened, itchy skin when stroked. These lesions tend to be more apparent on the areas of skin exposed to pressure or rubbing. When cases begin during childhood, the skin tends to be affected more than the other organs. Blistering of the skin lesions is seen exclusively in children younger than two years of age. Diffuse cutaneous mastocytosis is another form of mastocytosis seen in children. The skin is diffusely thickened and discolored, generally without individual distinct lesions in this form of mastocytosis.

Flushing and gastric acid hypersecretion due to mast cell-associated histamine are common complaints. Heartburn, stomach aches and diarrhea may occur. The liver, spleen and lymph nodes may become enlarged in a subset of patients. Bones affected by mastocytosis may become softened and deteriorate, although some new bone growth may occur with thickening of the outer portions or spongy inner areas of the bones. Massive mast cell degranulation may lead to life-threatening episodes of anaphylaxis. The most common triggers include, but are not limited to, certain medications like aspirin and other non-steroidal anti-inflammatory drugs, narcotics, radiocontrast material, and insect stings. These are similar in nature to severe allergic reactions and may involve hypotension, increased heart rate and loss of consciousness. Patients with an associated hematologic disorder may have symptoms of that disorder such as fatigue and weight loss.


A genetic alteration (mutation) resulting in the overactivation of the receptor for mast cell growth factor (c-kit) has been identified in the abnormal mast cells in adult-onset mastocytosis. This mutation is believed to cause the abnormal accumulation of mast cells in certain tissues. The release of mediators produced by mast cells, such as histamine, heparin and prostaglandin D2, results in symptomatic episodes. Histamine is a natural chemical normally released during an allergic event that causes itching, wheezing, dilation of blood vessels, and hypersecretion of stomach acid.

Affected Populations

Mastocytosis affects males and females in equal numbers. It can begin during childhood or adulthood. Childhood-onset disease most commonly starts in the first two years of life.

Standard Therapies

In October 2006, the FDA granted expanded approval to treat aggressive systemic mastocytosis with the cancer drug imatinib mesylate (Gleevec). For information on Gleevec, contact the drug's manufacturer, Novartis, at:

Novartis International AG


Basel, Switzerland

Treatment of mastocytosis is directed at controlling the symptoms caused by mast cell mediators. H1 and H2 antihistamines are therefore cornerstones of the treatment. Cromolyn sodium can be especially effective for the treatment of some gastrointestinal symptoms. PUVA treatment may cause temporary attenuation of the urticaria pigmentosa lesions. Steroids may be necessary in selected patients unresponsive to standard therapy.

Subcutaneous injections of epinephrine can be self-administered by the patient in cases of severe anaphylactic episodes. This therapy should always be followed by evaluation of the patient in a medical facility.

Associated hematologic disorders should be treated by a blood specialist (hematologist).

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010


For information about clinical trials sponsored by private sources, contact:

For information about clinical trials conducted in Europe, contact:



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The Mastocytosis Society, Inc.

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