Systemic mastocytosis (mas-to-sy-TOE-sis) is a rare condition that results in too many mast cells building up in the body. Mast cells are found in tissues throughout the body. Mast cells help the immune system work properly and help protect the body from disease.

Systemic mastocytosis causes too many mast cells to build up in the skin and bone marrow. Less often, mast cells also build up in the digestive tract or other body organs.

When triggered, these mast cells let out too much histamine and other chemicals into the body, which can cause symptoms like those of an allergic reaction. Sometimes, severe swelling and irritation, called inflammation, results in organ damage. Common triggers include alcohol, insect stings, physical and emotional stress, and certain medicines.

Symptoms of systemic mastocytosis depend on the part of the body affected. Too many mast cells can build up in the skin, bone marrow, liver, spleen or intestines. Less commonly, other organs such as the brain, heart or lungs may be affected.

Symptoms of systemic mastocytosis may include:

• Flushing, itching or raised bumps on the skin called hives.
• Dizziness, fainting or headache.
• Fast heartbeat or a heartbeat that isn't regular.
• Stuffy nose, shortness of breath or a whistling sound when breathing out called wheezing.
• Belly pain, diarrhea, upset stomach or vomiting.
• Bone or muscle pain.
• Severe tiredness.
• Depression, irritability, anxiety, or trouble thinking and paying attention.
• Bigger than usual liver, spleen or lymph nodes.

Types of systemic mastocytosis

Systemic mastocytosis most commonly occurs in adults. The condition usually includes skin symptoms and affects at least one other organ such as the bone marrow, liver or digestive tract.

The main types of systemic mastocytosis include:

• Indolent systemic mastocytosis. This is the most common type. Skin symptoms are common. Other organs may be affected, but the condition usually doesn't affect how well organs work. This type may worsen slowly over time.
• Smoldering systemic mastocytosis. This type involves more-serious symptoms. It may affect how organs work, and the condition worsens over time.
• Bone marrow mastocytosis. This type affects only the bone marrow and does not have skin symptoms. Too many mast cells in the bone marrow cause allergic reaction symptoms that happen often and can be severe. This type also causes weakened and brittle bones, called osteoporosis.

Advanced systemic mastocytosis is rare and includes these types:

• Systemic mastocytosis with a myeloid or hematologic neoplasm. This is systemic mastocytosis along with a blood or bone marrow condition, such as cancer. This severe type develops rapidly. It affects how well organs work and can cause organ damage.
• Aggressive systemic mastocytosis. This type has severe symptoms. It usually affects how well organs work and causes organ damage.
• Mast cell leukemia. This is a very rare and aggressive form of systemic mastocytosis.

Skin mastocytosis

Skin mastocytosis, also called cutaneous mastocytosis, typically occurs in children and usually affects only the skin. Cutaneous mastocytosis generally doesn't lead to systemic mastocytosis. For children, skin symptoms often go away during the teen years. This type also can occur in adults.

When to see a doctor

Talk to your healthcare professional if you have flushing or hives or if you have concerns about other symptoms that could be mastocytosis.

Most often systemic mastocytosis is caused by a random change in the KIT gene. Usually, this change in the KIT gene is not passed down in families.

The gene change causes the body to make too many mast cells. These cells build up in tissues and organs. When triggered, the mast cells let out chemicals into the body, such as histamine, leukotrienes, tryptase and cytokines. These chemicals cause inflammation and symptoms like those of an allergic reaction.

Having a change in the KIT gene is a risk factor for mastocytosis. For people with mastocytosis, being around triggers can raise the risk of symptoms. When triggered, mast cells let out chemicals into the body that cause inflammation and symptoms like those of an allergic reaction. People have different triggers, but the most common ones include:

• Insect stings.
• Skin irritation.
• Sudden temperature changes.
• Emotional stress.
• Exercise or physical strain.
• Certain medicines.
• Alcohol.

Complications of systemic mastocytosis can include:

• Severe allergic reaction. Called anaphylaxis, this severe allergic reaction includes symptoms such as rapid heartbeat, trouble breathing, fainting, loss of consciousness and shock. Anaphylaxis may lead to death if not treated right away. If you have a severe allergic reaction, you may need a shot of epinephrine.
• Blood disorders. These can include not having enough red blood cells, called anemia, and poor blood clotting that can result in bleeding.
• Peptic ulcer disease. Ongoing stomach irritation can lead to ulcers and bleeding in the digestive tract.
• Low bone density. Because systemic mastocytosis can affect the bones and bone marrow, this may raise the risk of bone conditions such as osteoporosis.
• Organ failure. A buildup of mast cells in body organs can cause inflammation and damage to the organs.

To diagnose systemic mastocytosis, your healthcare professional talks with you about your symptoms and medical history, including any medicines you've taken. Tests look for high levels of mast cells or the chemicals they let out into the body. Any organs that may be affected by the condition can be checked.

Tests may include:

• Blood or urine tests.
• Bone marrow biopsy. A biopsy is removing a small sample of tissue for testing in the lab.
• Skin biopsy.
• Imaging tests such as an X-ray, ultrasound, bone density scan and CT scan.
• Checking organs affected by the condition, such as the liver. This may involve doing a biopsy, if needed.
• Genetic testing.

Treatment may vary, depending on the type of systemic mastocytosis and the body organs affected. Treatment generally includes controlling triggers to avoid symptoms, treating the condition with options such as medicines, chemotherapy and stem cell transplant, and regular monitoring.

Controlling triggers

Identifying and avoiding factors that may trigger your mast cells, such as medicines or insect stings, can help you manage your systemic mastocytosis symptoms.

Medicines

Your healthcare professional may recommend medicines to:

• Treat allergic reaction symptoms, for example, with antihistamines.
• Lessen stomach acid and discomfort in your digestive system.
• Lessen the effects of the chemicals let out into your body by mast cells, for example, with corticosteroids.
• Control the KIT gene to lessen the number of mast cells made.
• Lessen bone loss.
• Lessen symptoms of depression or anxiety, for example, with antidepressants.

A healthcare professional can teach you how to give yourself an epinephrine shot if needed. The shot helps if you have a severe allergic response when your mast cells are triggered.

Chemotherapy

If you have aggressive systemic mastocytosis, or systemic mastocytosis with a blood or bone marrow condition, you may be treated with chemotherapy medicines to lower the number of mast cells in your body.

Stem cell transplant

In leukemia-related systemic mastocytosis, a stem cell transplant may be an option.

Regular monitoring

Your healthcare professional regularly monitors your condition using blood and urine tests. You may be able to use a special home kit to collect blood and urine samples while you're having symptoms. This gives your healthcare professional a better picture of how systemic mastocytosis affects your body. Regular bone density measurements can look for bone loss or signs of osteoporosis.

Systemic mastocytosis can be a complex condition. Understanding your condition is critical to ongoing care and preventing complications. Ask family or friends if they can help you monitor and care for your condition. Here are some self-care tips:

• Identify and avoid your triggers.
• Treat allergic reactions. If your healthcare professional recommends epinephrine, always carry one or two doses with you.
• Follow your healthcare professional's recommended care and ongoing monitoring.
• Wear a medical alert bracelet or necklace or carry a medical card identifying that you have systemic mastocytosis. Ask your healthcare professional to give you information about your condition that you can carry with you. Give it to healthcare professionals in case you need emergency care.

Consider these tips for managing systemic mastocytosis, a lifelong condition:

• Learn about the condition. Learn as much as you can about systemic mastocytosis. Then you can make the best choices and speak up for yourself. Help your family members and friends understand your condition, your care needs and the safety precautions you need to take.
• Find a team of trusted professionals. You'll need to make important decisions about care. Medical centers with specialty teams can offer you information about systemic mastocytosis, as well as advice and support, and can help you manage care.
• Seek out other support. Talking to people who also have systemic mastocytosis or other lifelong conditions can give you information and emotional support. Ask your healthcare professional about resources and support groups in your community. If an in-person support group isn't for you, your healthcare professional may be able to put you in touch with someone who has systemic mastocytosis. Or you may be able to find a group or individual support online.
• Ask for help. Ask for or accept help from family and friends when needed. Take time for your interests and activities. Counseling with a mental health professional may help with anxiety, depression and coping strategies.

You may start by talking with your family healthcare professional. Or you may be referred to a specialist in allergy and immunology called an allergist or a specialist in blood conditions called a hematologist.

Ask a trusted family member or friend to go with you to the appointment. That person can offer emotional support and help you remember the details.

Here's some information to help you get ready for your first appointment.

What you can do

Before your appointment, make a list of:

• Your symptoms, including when they began and what seems to make them worse or better.
• Medical conditions you've had and their treatments.
• All medicines, vitamins, herbal supplements and dietary supplements you take.
• Questions you want to ask the healthcare professional.

Questions to ask may include:

• What likely is causing my symptoms?
• Are there other possible causes for these symptoms?
• What kinds of tests do I need?
• Should I see a specialist?

What to expect from your doctor

Your healthcare professional may ask questions such as:

• What symptoms do you have?
• When did your symptoms start?
• Do you have allergies? Have you had any allergic reactions?
• What triggers your allergy?
• What seems to make your symptoms worse? What seems to make your symptoms better?
• Have you been diagnosed or treated for any other medical conditions?

Be ready to answer questions so that you have time to talk about what's most important to you.

Types of systemic mastocytosis

The five main types of systemic mastocytosis include:

• Indolent systemic mastocytosis. This is the most common type and usually doesn't include organ dysfunction. Skin symptoms are common, but other organs may be affected, and the disease may worsen slowly over time.
• Smoldering systemic mastocytosis. This type is associated with more-significant symptoms and may include organ dysfunction and worsening disease over time.
• Systemic mastocytosis with another blood or bone marrow disorder. This severe type develops rapidly and is often associated with organ dysfunction and damage.
• Aggressive systemic mastocytosis. This rare type is more severe, with significant symptoms, and is usually associated with progressive organ dysfunction and damage.
• Mast cell leukemia. This is an extremely rare and aggressive form of systemic mastocytosis.

Systemic mastocytosis most commonly occurs in adults. Another type of mastocytosis, cutaneous mastocytosis, typically occurs in children and usually affects only the skin. It generally doesn't progress to systemic mastocytosis.