Systemic Mastocytosis

Medically Reviewed by Nayana Ambardekar, MD on March 13, 2023
7 min read

If your doctor says you have systemic mastocytosis, it means you have a disease where too many abnormal mast cells -- a type of white blood cell -- build up in your skin and organs. You might get a variety of symptoms, including things like itchy skin, a bellyache, a rapid heartbeat, feeling light-headed, and other problems. There's no cure, but treatments can help you manage the condition.

Mast cells are part of your immune system. They help fight off illness and heal wounds. With systemic mastocytosis, extra mast cells can gather in different parts of the body, including your skin, bone marrow, bones, and digestive tract.

Certain triggers set off these mast cells and lead them to release chemicals, such as histamines, which cause flushing of the face, neck, and chest, along with itching, hives, and other symptoms.

If you have a serious episode, systemic mastocytosis can get in the way of how your organs work. In some cases, the mast cells may cause an allergic reaction called anaphylaxis that is sometimes life-threatening. If that happens to you, you'll need to get medical help right away and use an epinephrine auto-injector.

It may be helpful to reach out to family and friends as you manage this disease. They can give you the support you need for the emotions and stress that can go along with meeting the challenges of a long-term condition like systemic mastocytosis.

Most of the time, systemic mastocytosis doesn't run in families. A random change (mutation) in the KIT gene shows up in mast cells in people with mastocytosis. This gene helps program a protein that's in charge of how cells grow. It also plays a role in the way mast cells develop.

Signs of systemic mastocytosis can show up at any age, but it usually happens when you're an adult. You're most likely to get a diagnosis when you're in your 40s or 50s.

If you have systemic mastocytosis, certain triggers cause mast cells to release chemicals and cause symptoms. They aren't the same for everyone, but common triggers include:

It's also possible to get symptoms without any triggers.

How you feel has something to do with the type of systemic mastocytosis you have. Your doctor will let you know which of five main types you have:

Indolent systemic mastocytosis (ISM). ISM gets worse slowly.

Systemic mastocytosis with an associated hematologic nonmast cell lineage disorder (SH-AHNMD). You have another blood disorder along with systemic mastocytosis.

Aggressive systemic mastocytosis (ASM). This type develops quickly and can damage your organs.

Mast cell leukemia (MCL). In this fast-growing disease, there's a large number of mast cells in your blood or your bone marrow -- the spongy center of your bones where blood cells are made.

Smoldering systemic mastocytosis. This type is associated with more-significant symptoms and may include organ dysfunction and worsening disease over time.

Your symptoms also depend on where in the body you have extra abnormal mast cells. For example, you may have a rash, itching, or get a flush if you have too many abnormal mast cells in your skin.

Your symptoms may show up after a trigger and then go away, or they can last a long time. Some problems you might get include:

You may also have some mental health concerns. For instance, you could have attention problems, anxiety, or depression. Experts aren't sure if these problems are because of a buildup of abnormal mast cells in the brain or the stress of living with systemic mastocytosis.

Your doctor will ask about your health history and do a physical exam. Based on your symptoms, you may need tests such as:

Skin biopsy. Your doctor removes a sample of your skin tissue and sends it to a lab. Technicians look at it under a microscope to check for a buildup of mast cells.

Bone marrow biopsy. Your doctor uses a needle to remove a sample of your bone marrow. A doctor called a hematologist, or another specialist, examines it for mast cells and looks for signs of other blood conditions.

Blood and urine tests. Doctors check your blood and urine to see if there are chemicals or substances related to mast cells. A test called a "complete blood count" can reveal if you have anemia or another blood disorder.

Genetic test. Lab technicians check a sample of your blood, bone marrow, or tissue to see if there are changes on the KIT gene.

Imaging tests. X-rays, ultrasounds, and CT scans may show problems like bone loss or an enlarged liver, spleen, or lymph nodes.

Endoscopy or colonoscopy. In an endoscopy or colonoscopy, a doctor puts a thin, flexible tube with a camera into the mouth or rectum. This can show ulcers, bleeding, and mast cell buildup in your digestive tract. Sometimes the doctor removes a sample of tissue and checks it for mast cells.

It helps to write down a list of questions and take it with you to your doctor's appointment. Some questions you might want to ask are:

  • What kind of systemic mastocytosis do I have?
  • What are my treatment options and their goals? What plan do you recommend, and why?
  • What are the possible side effects of my treatment?
  • Could I have a dangerous allergic reaction, and what should I do if I have one?
  • What can I do at home to relieve my symptoms?
  • Are there any medicines or activities that I should avoid?
  • What follow-up tests or visits will I need, and how often will I need them?


Your doctor will tailor your treatment plan to your symptoms, the organ that's affected, and the kind of systemic mastocytosis you have. The treatments may include:

Antihistamines. These drugs may relieve skin reactions -- such as flushing and itching -- and digestive system symptoms.

Epinephrine. This hormone treats anaphylaxis.

Proton pump inhibitors. These medicines curb stomach acid, which may ease some of the digestion problems you may get.

Mast cell stabilizers. These drugs, such as cromolyn sodium and ketotifen, block mast cells from releasing histamines.

Steroids. They may help with skin, nasal, and respiratory symptoms and can be part of your treatment if you get anaphylaxis.

Targeted therapy. These drugs target a specific gene, protein, or tissue involved in the disease. For systemic mastocytosis, your doctor may suggest a tyrosine kinase inhibitor to block a specific protein. You may need this kind of treatment if you have serious or life-threatening symptoms. Monoclonal antibody therapy can help manage symptoms once mast cells are activated.

Chemotherapy. You may need this treatment if your systemic mastocytosis is fast-moving and you have significant damage to your organs. You take these drugs through an IV or by mouth. They kill cancer cells throughout your body.

Stem cell transplant or bone marrow transplant. In rare cases, your doctor may consider this treatment. During this surgery, your bone marrow cells are replaced with healthy bone marrow or stem cells.

One of the best ways to manage systemic mastocytosis is to steer clear of triggers. You'll want to talk to your doctor and keep track of all the things that cause your symptoms, such as stress or spicy food.

Because the disease can cause a life-threatening allergic reaction, you'll also want to carry an epinephrine auto-injector at all times.

How your disease develops depends a lot on the type of systemic mastocytosis you have. ISM, for instance, is the mildest kind. Your symptoms will slowly get worse.

The more serious types, such as ASM and MCL, move more rapidly. For ASM, you may need treatment for problems like bone loss. If you have MCL, which is a rare type, you may get blood disorders, including leukemia.

Whatever type you have, after your diagnosis, you'll go to regular follow-up appointments with your doctor. They'll want to monitor your disease and check that your treatments are working.

When you're managing a condition like systemic mastocytosis, you may sometimes find that you feel like you're on an emotional rollercoaster. If that's the case with you, it's OK to look beyond your circle of family and friends to get the backing you need.

A support group can be a huge help in this situation. You'll get to talk to other people who understand what you're going through. These groups meet in person, on the telephone, or online.

To find a group, you can ask your doctor, social worker, or other people with systemic mastocytosis. Or you can go to the websites of The Mastocytosis Society, RareConnect, and Mast Cell Action.

If you find that the challenges of managing your disease are making you depressed or anxious, talk to your doctor. They can put you in touch with mental health professionals who are experts in treating these problems.