Systemic Mastocytosis

Everyone has mast cells, a kind of immune cell that plays an important role in your body’s defense mechanism. Think of them as first responders. They spring to action when allergens and other invaders attack your body. They multiply and get to work — creating something called histamine to trigger an allergic response.

Sometimes, though, these cells multiply even when there are no intruders. This can set off a constant allergic response (too many histamines all the time) that can affect your skin, bone marrow and internal organs. You can get rashes, bone pain, headaches, heart palpitations, itching, fatigue, bruising and stomach ulcers. You could also have mood swings and depression. Symptoms can come and go suddenly (mastocytosis attacks).

Types of systemic mastocytosis

There are six types of systemic mastocytosis:

• Indolent systemic mastocytosis: The most common one, it typically progresses very slowly and doesn’t affect your organs.
• Systemic smoldering mastocytosis: This affects your liver, spleen and lymph nodes.
• Systemic mastocytosis with hematologic neoplasm: It can be present with a second blood cancer, like myelodysplastic syndrome.
• Aggressive systemic mastocytosis: This happens when too many mast cells in your bone marrow make it hard for the bone marrow to make blood cells. Low numbers of blood cells can affect your liver, spleen, digestive tract and cause weak or broken bones (fractures) and bone lesions.
• Mast cell leukemia or sarcoma: The least common, but most severe, type.
• Mast cell sarcoma: Rarely, tumors can grow from abnormal mast cells in your body’s tissues.

Diagnosing Systemic Mastocytosis at Cleveland Clinic

Not only are there many types of systemic mastocytosis, but its symptoms are similar to those of other conditions. So, it can easily be confused with other things.

Our mastocytosis experts follow the latest National Comprehensive Cancer Network^® guidelines when making a diagnosis. These guidelines help us more accurately figure out what kind of SM you have, if it’s cancerous and how bad it is (its stage).

What to expect at your first visit

When you come to Cleveland Clinic for your first visit, we’ll want to hear all about what’s going on with you — from the first time you noticed symptoms to how they affect your life.

This information helps us pinpoint what’s going on and craft a highly individualized treatment plan focused not just on your test results and diagnosis, but also on your unique needs and goals.

You can expect to have a physical exam so we can check out your symptoms and look for signs of SM. We’ll also order some tests to help further confirm our diagnosis:

Blood tests

Blood tests can measure a blood enzyme (tryptase) that mast cells make to help fight invaders. High levels of this enzyme could point to systemic mastocytosis. We’ll do a complete blood count (CBC) to measure:

• Platelets.
• Red blood cells.
• White blood cells.

We’ll also run tests to see how well your organs work, including your liver, spleen and kidneys.

Biopsy

We may do a skin biopsy, bone marrow biopsy or organ biopsy to see if you have really high numbers of mast cells. A pathologist (cell and tissue specialist) will examine a small sample of skin or bone marrow under a microscope to look for abnormal mast cells.

Imaging exams

We may use imaging exams to get a closer look at your bones, liver, spleen and digestive organs. These can include:

• CT scan.
• Ultrasound.
• X-ray.
• Bone scan.

Genetic testing

Systemic mastocytosis is usually linked to an abnormal gene called KIT. We can do genetic testing to find out if you have the mutation (change in a gene that makes it abnormal). You aren’t born with the mutation. It can happen at any time after birth. So, having the abnormal gene doesn’t mean you’ll pass on the condition to your children.

Meet Our Systemic Mastocytosis Team

If you choose Cleveland Clinic, you’ll benefit from our team-based approach to care. We carefully choose providers from different specialties for your healthcare team — and all will have experience in treating uncommon blood conditions like SM. Your team will depend on the type of SM you have, your symptoms and your needs. It could include:

• Hematologists.
• Allergists.
• Oncologists.
• Gastroenterologists.
• Pathologists.
• Nurse practitioners.
• Physician assistants.

These providers (and possibly others) work together to confirm a diagnosis and build the right treatment plan for your needs, health and goals.

Treatment for systemic mastocytosis depends on how it’s affecting you and your health. Your care team works with you to customize a treatment plan aimed at helping you manage symptoms and prevent serious complications — like anaphylaxis or anemia.

To do this, our systemic mastocytosis specialists may recommend treatments like:

• Antihistamines: Relieve skin irritation like itching, hives and swelling.
• Corticosteroids and immunosuppressants: Reduce inflammation.
• Epinephrine: Treats anaphylaxis.
• Bisphosphonates: Help with bone weakness.
• Targeted therapy: Changes how mast cells grow, multiply and survive. They target the KIT gene. Two approved therapies include midostaurin and avapritinib. For some people without the KIT gene mutation, imatinib is used.
• Chemotherapy: Destroys cancerous mast cells.
• Bone marrow transplant: Can offer a chance for a cure in aggressive or advanced SM cases.
• Surgery: Removes skin growths or an enlarged spleen (splenectomy).
• Clinical trials: Help us study new and emerging cancer research. Your provider can let you know if you’re eligible to take part in a clinical trial.

Taking the Next Step

When you have systemic mastocytosis, your allergy response kicks into overdrive and decides to fight you. All day and night. This can leave you feeling itchy, sick, exhausted and even lead to internal organ damage. Cleveland Clinic’s experienced providers can help. We’ll work with you to craft a personalized treatment plan that will help you manage your SM symptoms and get you the relief you need.