Systemic Mastocytosis

What is systemic mastocytosis?

Systemic mastocytosis is a type of mastocytosis — a rare blood disorder that happens when your body makes abnormal mast cells. Mast cells are a type of white blood cell and part of your immune system.

When mast cells detect intruders, they release histamine. Histamine sets off an allergic response. Normally, mast cells stop releasing histamine when their job is done. But in systemic mastocytosis, large numbers of abnormal mast cells continue to release histamine long after they should. This chemical overload causes a continuous allergic response that can affect your skin and internal organs.

Systemic mastocytosis is rare. It affects about 13 out of every 100,000 people worldwide.

People with systemic mastocytosis have a higher risk of anaphylaxis (a severe, life-threatening allergic reaction). Rarely, systemic mastocytosis can become cancer.

Healthcare providers can’t cure the condition. But treatment can ease your symptoms.

Types of systemic mastocytosis

There are six types of systemic mastocytosis. Each can affect you in different ways. In general, the more abnormal mast cells you have, the greater the chance you’ll have complications.

These types include:

• Indolent systemic mastocytosis. This is the most common type. Symptoms usually develop over several years. Abnormal mast cells increase. This causes symptoms that affect your skin, liver, spleen and gastrointestinal tract.
• Systemic smoldering mastocytosis. In this type, abnormal mast cells multiply in your liver and spleen. Eventually, the cells may cause an enlarged spleen or enlarged liver.
• Systemic mastocytosis with associated hematologic neoplasm. People with this type develop blood disorders like myeloproliferative neoplasms and myelodysplastic syndrome. This type affects about one-fifth of people with systemic mastocytosis.
• Aggressive systemic mastocytosis. This type can affect your bone marrow and bones. Abnormal mast cells can 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. Tumors made of abnormal mast cells attack tissue. Very few people with systemic mastocytosis develop mast cell sarcoma.

What are the symptoms of systemic mastocytosis?

Symptoms vary depending on where the abnormal mast cells gather. For example, if you have too many mast cells in your stomach, you might develop ulcers and belly pain. In the same way, abnormal mast cells that build up in your bone marrow may affect blood cell production.

Systemic mastocytosis symptoms may include:

• Anemia
• Bone pain
• Excessive bleeding
• Fatigue
• Flushed skin
• Heart palpitations
• Hives
• Itchy skin
• Mood changes or depression
• Urticaria pigmentosa (dark, itchy bumps on your skin)

People with systemic mastocytosis may suddenly develop several symptoms all at once. Healthcare providers may refer to this as a mastocytosis attack or flare.

Having these symptoms doesn’t necessarily mean you have systemic mastocytosis. But if you have several of these symptoms at the same time and they don’t go away, talk to a healthcare provider.

What causes systemic mastocytosis?

Research shows about 80% of people with systemic mastocytosis have a KIT gene variant (change). KIT genes play a role in developing certain cell types, including blood cells and mast cells. The gene change happens after conception and isn’t hereditary.

Risk factors

Many things can trigger systemic mastocytosis. Not everyone with the condition reacts to the same triggers, but common ones include:

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

Ask your healthcare provider which triggers you should avoid.

How is systemic mastocytosis diagnosed?

A healthcare provider will start with a physical exam. They’ll ask about your symptoms and medical history.

They may also run one or more of the following tests to diagnose or rule out systemic mastocytosis:

• Blood tests to check on the amount of tryptase in your blood (an enzyme that mast cells release when they react to intruders)
• Bone scans to look for signs of bone damage
• Bone marrow biopsy to look for unusual numbers of mast cells in your bone marrow
• Genetic tests to check for a KIT gene variant

How is systemic mastocytosis treated?

Healthcare providers treat systemic mastocytosis by managing symptoms and complications. For example, if you have excess stomach acid, they may prescribe H2 blockers (antacids). If the condition causes anemia, they’ll treat the anemia.

Systemic mastocytosis treatments may include:

• Antihistamines to relieve itching, flushing and other skin reactions
• Corticosteroids to reduce inflammation
• Bisphosphonates to help with bone weakness
• Targeted therapy, which focuses on the protein in abnormal mast cells
• Chemotherapy, if systemic mastocytosis becomes cancerous
• Splenectomy to remove an enlarged spleen
• Bone marrow transplant to treat aggressive or advanced systemic mastocytosis

If you have systemic mastocytosis, you should always carry an EpiPen^®. Epinephrine treats anaphylactic shock, a severe, life-threatening allergic reaction.

Can systemic mastocytosis be prevented?

Systemic mastocytosis happens when you have the genetic change that causes it. That means you can’t prevent it. But you can reduce your risk for attacks or flares by avoiding triggers.

What can I expect if I have systemic mastocytosis?

There’s no cure for systemic mastocytosis. But healthcare providers have treatment strategies to manage symptoms and complications.

A bone marrow transplant can permanently get rid of systemic mastocytosis. But healthcare providers reserve this treatment for those with the most aggressive forms of the condition.

What’s the outlook for systemic mastocytosis?

That depends on the condition type. People with indolent systemic mastocytosis can usually manage their condition with treatment. They have a typical life expectancy. Those with more aggressive types may have shorter lifespans.

How do I take care of myself?

Knowing how to avoid triggers is a big part of living with systemic mastocytosis. If you have this condition, you should:

• Always carry an EpiPen to treat severe, life-threatening allergic reactions.
• Know your triggers and do your best to avoid them.
• Manage stress by practicing meditation or other forms of mindfulness.
• Wear a medical alert bracelet that lists medications you can’t take.

When should I see my healthcare provider?

You’ll see your healthcare provider for regular check-ups. Be sure to tell them whenever you notice new or worsening symptoms.

What questions should I ask my doctor?

Systemic mastocytosis is rare. Here are some questions you might want to ask your healthcare provider:

• 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 treatments make my symptoms go away?
• Are there clinical trials I should consider?