Systemic Mastocytosis

Systemic mastocytosis is a rare blood disorder. It happens when your body makes abnormal mast cells that multiply. Mast cells defend against intruders such as allergens. In systemic mastocytosis, abnormal mast cells set up a continuous allergic response. The cells also multiply uncontrollably, affecting your skin and internal organs.


Rash with noticeable raised section on left side that’s a sign of systemic mastocytosis.
People with systemic mastocytosis may develop raised spots or rashes on their skin. When touched or stroked, the area of skin affected by the rash may turn red and start to itch or swell.

What is systemic mastocytosis?

Systemic mastocytosis is a rare blood disorder. It happens when your body makes abnormal mast cells. Mast cells are white blood cells and part of your immune system. They’re first responders when allergens and other intruders attack your body. In systemic mastocytosis, abnormal mast cells multiply, setting up a continuous allergic response that may affect your skin and internal organs.

Healthcare providers can’t cure systemic mastocytosis, but they can treat symptoms and complications the condition causes. Most people with systemic mastocytosis have mild symptoms they can manage with medication and by avoiding activities that trigger the condition. Rarely, systemic mastocytosis symptoms get worse or become cancer. All people with this condition have an increased risk of anaphylaxis. This is a severe allergic reaction that can be life-threatening.

How does this condition affect my body?

You have mast cells throughout your body, mostly in your skin, lungs and the lining of your intestine. Mast cells protect your body from intruders such as bacteria and allergens. Mast cells also help produce stomach acid.

When mast cells detect intruders, they release histamine. Histamine sets off an inflammatory (allergic) response. At the same time, small sacs within each mast cell called mediators release substances to defend against intruders.

Normally, mast cells and mediators stop their work after dealing with intruders. In systemic mastocytosis, you have large numbers of abnormal mast cells continually releasing histamine and other substances. This chemical overload can cause a range of issues.

For example, abnormal mast cells that build up in your bone marrow may affect blood cell production. Likewise, unusually large numbers of mast cells affect organ function. For example, if there are unusually large numbers of mast cells in your stomach, they may produce too much stomach acid and cause ulcers.

Systemic mastocytosis typically affects adults. Another type of mastocytosis — cutaneous mastocytosis — typically affects children.

There are six systemic mastocytosis types. Each type may affect you in different ways. In general, the more abnormal mast cells you have, the greater the chance you’ll have serious health issues. Systemic mastocytosis types include:

  • Indolent systemic mastocytosis: This is the most common type of systemic mastocytosis. Indolent systemic mastocytosis symptoms develop over several years. As the number of abnormal mast cells slowly increases, you may notice changes in your skin, liver, spleen and gastrointestinal tract. Most people with indolent systemic mastocytosis manage their symptoms with medication and have normal lifespans.
  • Systemic smoldering mastocytosis: Abnormal mast cells multiply in your liver and spleen. Eventually, the cells may cause an enlarged spleen (splenomegaly) or enlarged liver (hepatomegaly).
  • Systemic mastocytosis with associated hematologic neoplasm: In this type, people develop blood disorders such as myeloproliferative neoplasms and myelodysplastic syndrome. This type affects about one-fifth of people with systemic mastocytosis.
  • Aggressive systemic mastocytosis: This type may affect your bone marrow and bones. As abnormal mast cells multiply in your bone marrow, they interrupt blood cell production. You may develop conditions such as low white blood cell numbers (leukopenia) and low red blood cell numbers (anemia). Abnormal mast cells may also grow into your bones, making them weak and more likely to break.
  • Mast cell leukemia: Very rarely, systemic mastocytosis becomes mast cell leukemia. This is a form of acute myeloid leukemia (AML).
  • Mast cell sarcoma: This condition involves tumors made of abnormal mast cells that attack tissue. Like mast cell leukemia, very few people with systemic mastocytosis develop mast cell sarcoma.
Is systemic mastocytosis a serious illness?

It can be. While most people don’t have severe types of systemic mastocytosis, they do have an increased risk of anaphylaxis. Some people may go into anaphylactic shock, which is life-threatening.

How common is this condition?

Systemic mastocytosis isn’t common. A 2018 population analysis concluded that 1 in 10,000 people in the U.S. has the condition.


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Symptoms and Causes

What are the symptoms?

Systemic mastocytosis symptoms vary depending on where the abnormal mast cells gather. For example, someone who has too many mast cells in their stomach may develop ulcers and have symptoms including belly pain. Common systemic mastocytosis symptoms include:

  • Flat red areas on your skin with many small bumps:Healthcare providers may refer to this as maculopapular skin lesions.
  • Urticaria pigmentosa:This condition causes dark-colored bumps that are very itchy.
  • Flushed face:Your face becomes very red for no reason.
  • Itching: This itch won’t go away when you scratch it. Scratching the itchy spot may cause raised red spots (hives).
  • Headache:Rapidly multiplying mast cells may cause headaches.
  • Heart palpitations:This is an irregular or unusually rapid beating of your heart.
  • Bone pain:Abnormal mast cells can affect bone tissue, causing osteoporosis.
  • Extreme fatigue:This is a symptom of anemia, which may happen if systemic mastocytosis affects your red blood cell count.
  • Excessive bleeding and bruising: Abnormal mast cells may affect blood cell production.
  • Psychological changes:Studies show about one-third of people with systemic mastocytosis develop mental health issues, including depression, mood changes and emotional instability.

People with systemic mastocytosis may suddenly develop several symptoms that come on at the same time and then go away. Healthcare providers may refer to this as a mastocytosis attack.

Many of these symptoms are similar to symptoms of other less serious illnesses. Having these symptoms doesn’t mean you have systemic mastocytosis. But if you have several of these symptoms at the same time and the symptoms keep happening, talk to a healthcare provider. They’ll evaluate your situation and determine what’s causing your symptoms.

What causes systemic mastocytosis?

Research shows about 80% of people with this condition have a mutated KIT gene. KIT genes play a role in developing certain cell types, including blood cells and mast cells. The mutation happens after conception and isn’t hereditary.

What triggers systemic mastocytosis?

Many things may trigger systemic mastocytosis. Not everyone with the condition reacts to the same triggers. If you have this condition, ask your healthcare provider what triggers you should avoid. Some common triggers include:

  • Rubbing or friction on your skin.
  • Exercise and physical activity.
  • Insect bites (especially ant bites) and wasp and bee stings.
  • Alcohol and spicy foods.
  • Certain medications, including nonsteroidal anti-inflammatory drugs (NSAIDs), muscle relaxers and anesthesia.
  • Sudden changes in temperature, like jumping into cold water.
  • Physical or emotional stress.


Diagnosis and Tests

How do healthcare providers diagnose systemic mastocytosis?

Providers may do the following tests to diagnose this condition:

  • Blood tests:Providers may do blood tests to check on the amount of tryptase in your blood. Tryptase is an enzyme that mast cells release when they’re reacting to intruders.
  • Bone scan: Providers may use a bone scan to look for signs of bone damage.
  • Bone marrow biopsy:Providers look for unusual numbers of mast cells in your bone marrow.
  • Genetic tests:Providers may test for a mutated KIT gene.

Management and Treatment

How do healthcare providers treat this condition?

Healthcare providers treat systemic mastocytosis by managing symptoms and complications. For example, they may prescribe H-2 blockers (antacids) to reduce symptoms caused by excess stomach acid. If systemic mastocytosis causes anemia, providers will treat the anemia. Treatments for symptoms may include:

  • Antihistamines: Antihistamines help relieve itching, flushing and other skin reactions.
  • Steroids: Providers may use steroids to reduce inflammation.
  • Bisphosphonates: This medication helps with bone weakness.
  • Targeted therapy: This treatment focuses on the protein in abnormal mast cells.
  • Chemotherapy: Rarely, mastocytosis types become cancerous. If that happens, providers treat the cancer with chemotherapy.
  • Splenectomy: If you have an enlarged spleen because of high mast cell numbers, providers may remove your spleen.
  • Bone marrow transplantation: In some instances, people with very aggressive or advanced systemic mastocytosis may be candidates for a bone marrow transplantation. A bone marrow transplantation may offer a chance for a cure.



How can I prevent this condition?

Systemic mastocytosis happens when a certain gene mutates soon after conception. That means you can’t prevent it. You can prevent systemic mastocytosis attacks by avoiding spicy foods and alcohol, certain medications and activities that trigger attacks.

Triggers vary from person to person, so you should ask your healthcare provider what triggers you should avoid. If certain medications trigger the condition, consider wearing a medical alert bracelet with information that lets other people know what medications you shouldn’t receive.

If you have systemic mastocytosis, you should always carry a self-injecting syringe of epinephrine, a hormone made by your adrenal glands. Epinephrine treats severe allergic reactions that could become life-threatening anaphylactic shock.

Outlook / Prognosis

Can healthcare providers cure systemic mastocytosis?

Systemic mastocytosis is considered an incurable disease. But healthcare providers have treatment strategies to manage symptoms and complications. Rarely, bone marrow transplantation may cure systemic mastocytosis. But this treatment is typically only available to a limited number of people who have a very advanced or aggressive form of systemic mastocytosis.

How long can you live with systemic mastocytosis?

That depends on the condition type. Typically, people with indolent systemic mastocytosis manage the condition with treatment and by avoiding triggers. They have a typical life expectancy. People with more aggressive condition types typically die a few years after diagnosis.

Living With

How do I take care of myself?

Self-care is a big part of living with the most common type of systemic mastocytosis. If you have this condition, you should:

  • Know what may trigger your mastocytosis attacks. Everyone’s triggers are different.
  • Emotional stress may trigger mastocytosis symptoms. If you need help managing your emotional stress, ask your healthcare to recommend programs for managing stress.
  • Wear a medical alert bracelet that lists your condition and medications you shouldn’t take.
  • Always carry a self-injecting syringe of epinephrine to treat severe and life-threatening allergic reactions.

When should I see my healthcare provider?

If you have systemic mastocytosis, your healthcare provider will monitor your treatment and symptoms with regular checkups. Contact your provider any time you notice new symptoms or your symptoms are worse.

When should I go to the emergency room?

Most people with systemic mastocytosis are able to manage symptoms. But you should go to the emergency room if your symptoms suddenly get worse.

What questions should I ask my healthcare provider?

Systemic mastocytosis is a rare illness. If you have this condition, you may want to ask your healthcare provider the following questions:

  • What type of systemic mastocytosis do I have?
  • What are additional symptoms that may be a sign my condition is getting worse?
  • What are treatments for the condition type I have?
  • Will I always need treatments?
  • Will treatments make my symptoms go away?
  • I have a more serious type of this condition. What’s my prognosis?
  • Are there clinical trials I should consider?

A note from Cleveland Clinic

Systemic mastocytosis is a rare blood disorder. It happens when your body makes abnormal mast cells that multiply, affecting your organs. Most of the time, people can manage systemic mastocytosis with medication and lifestyle changes. But this condition increases the risk of life-threatening anaphylactic shock, a very severe allergic reaction. People with systemic mastocytosis should have self-injecting syringes of epinephrine at hand to treat severe allergic reactions.

Medically Reviewed

Last reviewed on 10/28/2022.

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