Systemic mastocytosis (mas-to-sy-TOE-sis) is a rare disorder that results in too many mast cells building up in your body. A mast cell is a type of white blood cell. Mast cells are found in connective tissues throughout your body. Mast cells help your immune system function properly and normally help protect you from disease.

When you have systemic mastocytosis, excess mast cells build up in your skin, bone marrow, digestive tract or other body organs. When triggered, these mast cells release substances that can cause signs and symptoms similar to those of an allergic reaction and, sometimes, severe inflammation that may result in organ damage. Common triggers include alcohol, spicy foods, insect stings and certain medications.

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

Signs and symptoms of systemic mastocytosis may include:

• Flushing, itching or hives
• Abdominal pain, diarrhea, nausea or vomiting
• Anemia or bleeding disorders
• Bone and muscle pain
• Enlarged liver, spleen or lymph nodes
• Depression, mood changes or problems concentrating

The mast cells are triggered to produce substances that cause inflammation and symptoms. People have different triggers, but the most common ones include:

• Alcohol
• Skin irritation
• Spicy foods
• Exercise
• Insect stings
• Certain medications

When to see a doctor

Talk to your doctor if you have problems with flushing or hives, or if you have concerns about the signs or symptoms listed above.

Most cases of systemic mastocytosis are caused by a random change (mutation) in the KIT gene. Typically this flaw in the KIT gene is not inherited. Too many mast cells are produced and build up in tissues and body organs, releasing substances such as histamine, leukotrienes and cytokines that cause inflammation and symptoms.

Complications of systemic mastocytosis can include:

• Anaphylactic reaction. This severe allergic reaction includes signs and symptoms such as rapid heartbeat, fainting, loss of consciousness and shock. If you have a severe allergic reaction, you may need an injection of epinephrine.
• Blood disorders. These can include anemia and poor blood clotting.
• Peptic ulcer disease. Chronic stomach irritation can lead to ulcers and bleeding in your digestive tract.
• Reduced bone density. Because systemic mastocytosis can affect your bones and bone marrow, you may be at risk of bone problems, such as osteoporosis.
• Organ failure. A buildup of mast cells in body organs can cause inflammation and damage to the organ.

To diagnose systemic mastocytosis, your doctor will likely start by reviewing your symptoms and discussing your medical history, including medications you've taken. He or she can then order tests that look for high levels of mast cells or the substances they release. Evaluation of organs affected by the condition also may be done.

Tests may include:

• Blood or urine tests
• Bone marrow biopsy
• Skin biopsy
• Imaging tests such as an X-ray, ultrasound, bone scan and CT scan
• Biopsy of organs affected by the disease, such as the liver
• Genetic testing

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.

Treatment may vary, depending on the type of systemic mastocytosis and the body organs affected. Treatment generally includes controlling symptoms, treating the disease and regular monitoring.

Controlling triggers

Identifying and avoiding factors that may trigger your mast cells, such as certain foods, medications or insect stings, can help keep your systemic mastocytosis symptoms under control.

Medications

Your doctor may recommend medications to:

• Treat symptoms, for example, with antihistamines
• Reduce stomach acid and discomfort in your digestive system
• Counteract the effects of the substances released by your mast cells, for example with corticosteroids
• Inhibit the KIT gene to reduce the production of mast cells

A health care professional can teach you how to give yourself an epinephrine injection in the event that you have a severe allergic response when your mast cells are triggered.

Chemotherapy

If you have aggressive systemic mastocytosis, systemic mastocytosis associated with another blood disorder or mast cell leukemia, you may be treated with chemotherapy medications to reduce the number of mast cells.

Stem cell transplant

For people who have an advanced form of systemic mastocytosis called mast cell leukemia, a stem cell transplant may be an option.

Regular monitoring

Your doctor regularly monitors the status of your condition using blood and urine samples. You may be able to use a special home kit to collect blood and urine samples while you're experiencing symptoms, which gives your doctor a better picture of how systemic mastocytosis affects your body. Regular bone density measurements can monitor you for problems such as osteoporosis.

Systemic mastocytosis can be a complex disease. Understanding your condition is critical to ongoing care and prevention of 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 doctor recommends epinephrine, always carry a dose with you.
• Follow your doctor'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 doctor to give you information for health care professionals that you can carry with you in case you need emergency care.

Caring for a lifelong disorder such as systemic mastocytosis can be stressful and exhausting. Consider these strategies:

• Learn about the disorder. Learn as much as you can about systemic mastocytosis. Then you can make the best choices and be an advocate for yourself. Help your family members and friends understand the condition, the care needed 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 are dealing with similar challenges can provide you with information and emotional support. Ask your doctor about resources and support groups in your community. If you don't feel comfortable in a support group, your doctor may be able to put you in touch with someone who has dealt with systemic mastocytosis. Or you may be able to find a group or individual support online.
• Ask for help from family and friends. 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 adjustment and coping.

While you may initially consult your family doctor, he or she may refer you to a doctor who specializes in allergy and immunology (allergist) or a doctor who specializes in blood disorders (hematologist).

Preparing and anticipating questions will help you make the most of your time with the doctor. Here's some information to help you get ready for your first appointment.

What you can do

Before your appointment, make a list that includes:

• Your symptoms, including when they began and if anything seems to make them worse or better
• Medical problems you've had and their treatments
• All medications, vitamins, herbal supplements and dietary supplements you take
• Questions you want to ask the doctor

Ask a trusted family member or friend to join you for the appointment. Take someone along who can offer emotional support and help you remember all of the information.

Questions to ask your doctor may include:

• What is likely causing my symptoms?
• Are there any 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 doctor may ask questions such as:

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

Your doctor will ask additional questions based on your responses, symptoms and needs. After getting detailed information about the symptoms and your family's medical history, your doctor may order tests to help with diagnosis and treatment planning.