Systemic mastocytosis

What causes systemic mastocytosis?

Most cases of systemic mastocytosis are caused by somatic mutations in the KIT gene. This gene encodes a protein that helps control many important cellular processes such as cell growth and division; survival; and movement. This protein is also important for the development of certain types of cells, including mast cells (immune cells that are important for the inflammatory response). Mutations in the KIT gene can leads to an overproduction of mast cells, which then accumulate in internal organs and lead to the symptoms of this condition.

Last updated on 05-01-20

How is systemic mastocytosis diagnosed?

A diagnosis of systemic mastocytosis (SM) is often suspected based on the presence of characteristic signs and symptoms. Additional testing can then be ordered to rule out other conditions with similar features; confirm the diagnosis; determine the type; and assess the severity. These tests may include:

More information about studies used to diagnose SM can be viewed here on the Medscape Reference website.

Last updated on 05-01-20

Is systemic mastocytosis inherited?

Most cases of systemic mastocytosis (SM) are sporadic (not inherited), occurring in people with no family history of the condition. The genetic mutations that often cause SM are somatic, which means they are acquired after conception and are only present in certain cells. Because they are not present in the germ cells (egg and sperm), they are not passed on to the next generation.

Rarely, SM has been reported in more than one family member. In this case, it may be inherited in an autosomal dominant manner. Mutations that cause autosomal dominant conditions are located in the germ cells. To be affected with an autosomal dominant condition, a person needs to have a mutation in only one copy of the responsible gene in each cell. A person with this form of SM has a 50% chance with each pregnancy of passing the mutation to his or her child.

Last updated on 05-01-20

Can heat and/or humidity affect systemic mastocytosis?

Yes. Heat appears to be one of the many factors that can trigger a mast cell response.

Other triggers include:

  • Certain medications
  • Physical factors, such as exercise, massage or friction applied to the skin, and very spicy foods
  • Surgical procedures
  • Alcohol
  • Infections
  • Stress
  • Insect stings

Last updated on 05-01-20

Do symptoms of indolent systemic mastocytosis (ISM) always worsen with time, or can people with ISM remain largely symptom-free?

Indolent systemic mastocytosis (ISM) typically progresses slowly or not at all. Symptoms do not always worsen with time. Although mast cell infiltrates can be detected in various organs (including liver, spleen, and gastrointestinal tract), the clinical course is generally indolent.

Fewer than 5% of people with an initial diagnosis of ISM will progress to a more severe form of systemic mastocytosis, such as:

Progression to one of these may occur within months to years from the initial diagnosis. Development of unexplained hematologic (blood-related) abnormalities, hepatosplenomegaly, unexplained weight loss, clotting disorders (coagulopathy), ascites, or gastrointestinal bleeding could mean there is a possibility of disease progression.

While most people with ISM have normal life expectancy, severe disability and death have been reported from anaphylactic episodes.

Last updated on 05-01-20

What is the long-term outlook for people with systemic mastocytosis?

The long-term outlook (prognosis) for people with systemic mastocytosis (SM) varies. Young children and those who present with primarily cutaneous (skin) and flushing symptoms tend to have little or no progression of the disease over a considerable length of time. Older patients and those with extensive, systemic disease involving other organ systems have a poorer prognosis. The median duration of survival is in these cases is not known but appears to be a few years.

Features that may be associated with a poorer prognosis may include:

  • elevated lactate dehydrogenase levels
  • anemia
  • thrombocytopenia (low platelet count)
  • hypoalbuminemia (low albumin)
  • excess bone marrow blasts (>5%)
  • high alkaline phosphatase
  • hepatosplenomegaly (enlarged liver and/or spleen)
  • ascites

Last updated on 05-01-20

How might systemic mastocytosis be treated?

Treatment for systemic mastocytosis (SM) is based on the signs and symptoms present in each person. For example, the following medications may used to treat various symptoms associated with SM:

  • Antihistamines to treat or prevent skin and gastrointestinal symptoms
  • Proton pump inhibitors to treat increased stomach acid
  • Epinephrine to treat anaphylaxis
  • Steroids to treat malabsorption (impaired ability to take in nutrients)
  • Mast-cell stabilizers such as ketotifen to treat some of the skin symptoms
  • Cromolyn sodium to treat gastrointestinal symptoms, bone pain, headaches, and some of the skin manifestations

If systemic mastocytosis is cancerous (mast cell leukemia) or associated with a blood disorder, steroids and/or chemotherapy may be necessary.

More specific information about treatment options can be accessed through the Treatment and Medication sections of the Medscape Reference website.

Last updated on 05-01-20

Name: The Mastocytosis Society P.O. Box 416
Sterling, MA, 01564, United States
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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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