This condition causes the body to produce too many mast cells, which are key players in the immune defense system. An excess number of these cells produces skin lesions, fatigue, decreased bone density, and bone or muscle pain.


As the number of oxygen-carrying red blood cells declines, patients may develop anemia, appearing pale, tired, or short of breath.

Chemicals released by mast cells can also lead to typical allergic responses such as flushing, itching, abdominal cramping, muscle pain, and even shock.

When mastocytosis affects the skin (cutaneous mastocytosis), patients may experience:

  • Tan or red-brown spots on the skin
  • Thickening of the skin
  • Blisters
  • Small lesions that do not itch

When mastocytosis affects areas other than the skin, it is call systemic mastocytosis. Patients may experience:

  • Skin lesions
  • Urticaria pigmentosa (also occurs in cutaneous mastocytosis)
  • Facial flushing (reddening of the face)
  • Itching
  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Ulcers in the stomach and duodenum (small intestine)
  • Headache
  • Lightheadedness
  • Heart palpitations (an irregular or unusually rapid beating of the heart)
  • Bone pain
  • Anemia (low red-blood cell count, which can cause fatigue)
  • Psychological changes (for example, irritability or an inability to concentrate)

Patients with systemic mastocytosis sometimes have "attacks,” when more than one symptom appears at the same time. Afterward they may feel tired and lethargic, complaining of drowsiness and low energy.


Cutaneous mastocytosis can be diagnosed by the appearance of the patient’s skin and confirmed by counting the number of mast cells appearing in a skin biopsy. To diagnose systemic mastocystosis, often a bone marrow biopsy is performed. Sometimes, the diagnosis is made in biopsies of other sites, like the intestine. After numbing the area, physicians insert a needle into the bone or tissue to extract the cells. They then examine those cells under a microscope and test them for certain genetic changes.

To confirm this diagnosis, a physician may order:

  • A test to measure protein (tryptase) in the mast cells
  • A test for specific genetic mutations associated with the disease

Systemic mastocytosis can take three forms:

  • The most common—indolent systemic mastocytosis—is a condition that progresses slowly
  • The second most common form is associated with a disruption of the bloodmaking (hematopoetic) process
  • The third form—aggressive systemic mastocyosis—progresses very quickly and can lead to organ damage

To confirm systemic mastocytosis, physicians may order further tests of the gastrointestinal tract, the bone marrow, or other organs.

Risk Factors

There is currently very little accurate data on significant risk factors for mastocytosis.

Mastocytosis is a rare condition, with only an estimated 5–10 new cases diagnosed for every million people in the US.

This condition most often occurs during infancy and early childhood. However, the risk of mastocytosis also increases during middle age. Most patients with this condition have an acquired C-kit receptor mutation. The C-kit receptor is a protein related to cell growth. It may cause the body to process excess mast cells.


Physicians use several medicines to treat the symptoms of this disease, including:

  • Epinephrine to address severe symptom flares related to shock, also referred to as anaphylaxis.
  • Antihistamines to help prevent the allergic skin reactions caused by the mast cells. Antihistamines can also relieve ulcerlike symptoms or alleviate severe low blood pressure before symptoms appear. or cromolyn sodium, to make the mast cells less sensitive to triggers.
  • Steroids are sometimes used in severe cases to help with symptoms
  • Some patients with systemic mastocytosis benefit from treatment with imatinib (Gleevec)

Mastocytosis is an area where there is active clinical research to develop new drugs.