Blood Disorders

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Mastocytosis

What is mastocytosis

Mastocytosis is a group of rare disorders caused by the presence of too many mast cells, or (mastocytes), which are part of the immune system. They are located in connective tissue, including the skin and other areas. They release histamines in the body that alert other immune defenses and are thought to play a role in wound healing. No one with too few or no mast cells has been found, which leads doctors to believe that people cannot survive without mast cells. In rare cases chemicals released by mast cells cause changes in the immune system leading to typical allergy symptoms such as: itching, abdominal cramping, or anaphylaxis (shock from allergic or immune causes). The increased number of mast cells in the tissues in mastocytosis is due to acquired genetic mutations in a protein called c-kit. Since this disease is an abnormal increased growth of genetically abnormal blood cells, mastocytosis is classified as a myeloproliferative neoplasm (MPN).

Symptoms and diagnosis

When too many mast cells exist in the body, skin lesions can occur, as can abdominal discomfort, low blood pressure, faintness, bone or muscle pain, nausea, and vomiting. The diagnosis can be expected from the clinical history and physical exam findings. Blood and urine tests are helpful for making the diagnosis and detecting the proteins produced by the mast cells call tryptase and histamine. Biopsies of affected tissue are needed to make the diagnosis. A bone marrow biopsy is commonly done to demonstrate more wide spread, or systemic, disease. Specific tests on biopsy samples are performed to detect the common mutation in the c-kit protein.

Treatment

Most cases of mastocytosis in adults are systemic (involving multiple sites) but are mild and do not require much therapy. Treatments are aimed at preventing the effects of the released disease mediators such as anti-histamines. Other medications stabilized the mast cells. Rarely do patients have more aggressive disease with organ involvement that causes low blood counts, liver failure, and malnutrition. For these patients, steroids and chemotherapy may be used but there are currently no good treatments. Newer drugs are being developed that act on the mutated c-kit or similar proteins.  Physicians at Seattle Cancer Care Alliance are participating in clinical trials to test these drugs.