Everything to Know About Mastocytosis

Medically Reviewed By Carissa Stephens, R.N., CCRN, CPN
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Mastocytosis is a type of mast cell disease. It causes a wide variety of symptoms that can involve one or more organs, such as the skin or digestive tract. The cause is a genetic mutation. Some mastocytosis symptoms can be similar to allergy symptoms, including anaphylaxis. There is currently no cure for mastocytosis, so treatment focuses on managing the symptoms.

This article provides details about mastocytosis, including the symptoms, causes, diagnosis, and treatment options.

What is mastocytosis?

school-age girl of East Asian descent looking down at her arm and scratching it

Mastocytosis is an accumulation of too many mast cells in one or more organ systems. Mast cells are white blood cells that release chemicals during immune and allergic responses. These chemicals include histamine, leukotrienes, and prostaglandins. With mastocytosis, the excessive amount of mast cells leads to an increased release of these chemicals.

Mast cells reside in connective tissue throughout the body. As a result, mastocytosis can affect any of the 10 organ systems, according to the Genetic and Rare Diseases Information Center. Mastocytosis can range from mild to severe.

Learn more about mast cells here.

What are the types of mastocytosis?

There are two main types of mastocytosis.

Cutaneous mastocytosis

Cutaneous mastocytosis only involves the skin. This type accounts for most cases. It is most common in children. Often, cutaneous mastocytosis improves or resolves by the time children reach adolescence.

Systemic mastocytosis

Systemic mastocytosis can affect many organ systems, including the skin. This type mainly affects adults. In many cases, there is skin involvement along with other organ systems. 

There are five subtypes of systemic mastocytosis. These are:

  • indolent, which is the mildest and most common form
  • smoldering, which is also a mild form but may involve more systems and have more severe symptoms than indolent
  • aggressive systemic, which is a severe form that results in problems with organ function — especially the liver, digestive tract, and bone marrow
  • systemic with associated hematologic neoplasm, which is more severe than aggressive systemic and involves a blood cell disorder or cancer
  • mast cell leukemia, which is the most severe and rarest form of mastocytosis

What are the signs and symptoms of mastocytosis?

Symptoms of cutaneous mastocytosis involve the skin. They can include:

  • small, brownish hives
  • inflamed, itchy skin
  • blisters
  • areas of rough, thickened skin

General symptoms

Systemic mastocytosis can cause general symptoms throughout the body. Symptoms depend on the organ system involved and may include:

Severe allergic reaction

Anaphylaxis can occur in both cutaneous and systemic mastocytosis. About 50% of people will have this type of reaction.

Anaphylaxis is a severe reaction to a trigger, such as an allergy, and is potentially life threatening. 

Symptoms can come on quickly and include: 

If you or someone around you develops these symptoms, you should: 

  1. Check to see whether they have an epinephrine pen. If they do, read and follow the instructions to dispense the medication.
  2. Dial 911 (or a local emergency number).
  3. Lay them down. If they have vomited, lay them on their side. 
  4. Stay with them until emergency services arrive. 

It is possible for someone to need more than one injection with an epinephrine pen. If symptoms do not begin to clear after 5 minutes, give a second injection if one is available.

What causes mastocytosis?

Mastocytosis usually occurs as a result of mutations in the KIT gene. This gene regulates the growth and survival of mast cells. A mutation in this gene stimulates the growth and division of mast cells. This leads to their excessive accumulation in mastocytosis.

The most common mutation is D816V. More than 90% of adults and 40% of children with mastocytosis have this mutation. 

People do not inherit or pass on the mutations that cause mastocytosis. Instead, these are acquired mutations that have formed during the person’s lifetime.


Typically, mast cells release their chemicals in response to an allergic or another immune system trigger. In mastocytosis, however, the increased number of mast cells leads to a massive release of chemicals in response to these allergens.

Another term to describe an allergen is “trigger.” Possible triggers include:

  • alcohol
  • spicy foods
  • certain ingredients, such as:
    • shellfish
    • eggs
    • soy
    • nuts
  • anxiety or stress
  • exercise
  • fatigue
  • friction
  • insect bites and stings
  • certain medications, including:
    • aspirin
    • muscle relaxants
    • opioids
    • nonsteroidal anti-inflammatory drugs
    • contrast dyes
  • infections, minor trauma, or surgery
  • temperature changes
  • vaccines

Risk factors

Mastocytosis affects males and females equally.

Also, both children and adults can get mastocytosis. In children, cutaneous mastocytosis is more common. Adults tend to get systemic mastocytosis.

How do doctors diagnose mastocytosis?

To diagnose mastocytosis, doctors start with a simple evaluation. This may include basic tests, such as:

  • a complete blood count
  • liver and kidney function tests
  • urinalysis

A more advanced evaluation is necessary to confirm the diagnosis. This includes a skin biopsy for cutaneous mastocytosis and a bone marrow biopsy for systemic mastocytosis. Biopsies of other organs may also be necessary.

Genetic tests can identify the D816V mutation if it is present in the KIT gene.

How do you treat mastocytosis?

Currently, there is no cure for mastocytosis. Instead, treatment is symptomatic. It aims to counter the effects of the mast cell chemicals. This mainly involves taking medications including:

  • antihistamines and H2 blockers, which are the cornerstone of treatment
  • antileukotriene drugs, such as montelukast (Singulair)
  • calcium, vitamin D, or bisphosphonates for bone strength
  • cromolyn sodium, which is a mast cell stabilizer
  • omalizumab (Xolair), which is a monoclonal antibody
  • proton pump inhibitors

People with mastocytosis should also have an epinephrine autoinjector for anaphylactic reactions.

Learn more about EpiPen, a brand of epinephrine, here.

For people with mastocytosis that is resistant to the above medications, doctors may try: 

  • cladribine (Mavenclad)
  • corticosteroids
  • interferon-alpha
  • tyrosine kinase inhibitors

Stem cell transplantation may also be an option for some people with severe forms of systemic mastocytosis.

Learn about stem cell transplants here.

What are the potential complications of mastocytosis?

Cutaneous mastocytosis is usually a benign condition without significant complications.

Systemic mastocytosis, on the other hand, can become cancerous. Other possible complications of systemic mastocytosis include:

  • anemia
  • liver and spleen enlargement
  • low platelets, leading to bleeding problems
  • organ damage or failure
  • recurrent anaphylaxis

What is the outlook for people with mastocytosis?

The outlook for children with cutaneous mastocytosis is generally good. Up to 80% of cases will resolve by adulthood. 

For adults with systemic mastocytosis, the outlook depends on the subtype. For example, indolent mastocytosis has a very low risk of progression. This risk increases with more severe forms. Mast cell leukemia has a poor outlook.

Living with mastocytosis

Living with mastocytosis requires being vigilant about potential allergens. When surgeries or other procedures are necessary, doctors must be sure to pre-medicate.

Also, everyone with mastocytosis should have an epinephrine autoinjector. It can be life saving when it is not possible to avoid allergens.

It is also important to wear medical identification jewelry so that others know how to help in an emergency.

Life expectancy

With mild systemic mastocytosis, life expectancy is similar to that of the general population. As the subtype severity increases, however, life expectancy decreases. Those with the most severe subtypes may survive for a few months or years after diagnosis.

Other frequently asked questions

Here are some other questions that people often ask about mastocytosis.

How rare is systemic mastocytosis? 

Mastocytosis is a rare disease. An estimated 3,000–30,000 people have the condition in the United States. 

Is mastocytosis curable?

At this time, there is no treatment that will cure mastocytosis.

Is mastocytosis cancerous? 

Systemic mastocytosis can become cancerous. Some adults with the condition will develop some form of cancer.

Is mastocytosis a form of leukemia? 

The most severe and rarest form of systemic mastocytosis is mast cell leukemia. Mast cell leukemia is an aggressive blood cancer


Mastocytosis is a rare disease involving mast cells. It causes an unusual accumulation of mast cells in the skin or another organ system.

When this increased number of mast cells release their chemical messengers, allergic and other symptoms can occur. This includes anaphylaxis, a life threatening condition.

Avoiding symptom triggers is an important part of living with mastocytosis. Although there is currently no cure, treatment can help manage the symptoms.

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Medical Reviewer: Carissa Stephens, R.N., CCRN, CPN
Last Review Date: 2022 Jul 5
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