SM Basics

All the information you need about systemic mastocytosis

FAQs

Systemic mastocytosis (SM) is a rare hematological disease characterized by the accumulation of mast cells in different parts of the body.

Read on for some frequently asked questions (FAQs) about SM, along with their answers.

Who can be diagnosed with SM?

SM seems to affect men and women equally. Adults are more likely to develop the disease compared to children. The disease also seems to be more common among people of Caucasian descent. 

What causes SM?

In most cases, SM is caused by a sporadic mutation in the KIT oncogene. 

Does SM run in families?

SM is not considered a genetic disease, and the mutation in the KIT oncogene occurs sporadically during the lifetime of a patient.

However, in very rare cases, the disease has been seen to be passed down in families.

Can environmental factors trigger SM?

Although the symptoms of SM can develop on their own without any external trigger, there may be some environmental factors that drive the development of an SM attack. 

These may include alcoholic drinks, certain foods like spicy foods, some medications like non-steroid anti-inflammatory drugs (NSAID), muscle relaxants and anesthetics, sudden changes in temperature, exercise and physical activity, insect bites and physical or emotional stress.

What are the early signs of SM?

The early signs of SM may include fatigue, muscle pain, low blood pressure, lightheadedness, nausea, headache, difficulty with memory and concentration and malaise. 

Some patients may also experience severe allergic reactions known as anaphylaxis.

How do doctors diagnose SM?

A diagnosis of SM can be reached based on the results of blood tests, imaging tests, bone marrow biopsy and genetic tests.

A definite diagnosis can be reached if at least one major and one minor criteria or three minor criteria established by the World Health Organization (WHO) are fulfilled. The major criterion is the presence of multifocal mast cell clusters in the bone marrow and/or extracutaneous organs. Minor diagnostic criteria include elevated serum tryptase levels, CD25/CD2/CD30 expression in mast cells and the presence of activating KIT mutations.

How common is SM?

SM is a rare disease. It is thought to affect one in 10,000 to 20,000 people worldwide.

What treatments are available?

There is currently no cure for SM, but there are some treatments that can alleviate the symptoms of the disease.

For milder forms of the disease, a doctor may prescribe antihistamines, corticosteroids or anti-immunoglobulin E antibodies such as omalizumab. 

Epinephrine may be used to treat sudden attacks of anaphylaxis.

For more severe forms of the disease, treatment may include cladribine, midostaurin, interferon-alpha, or tyrosine kinase inhibitors such as imatinib.

In the case of aggressive disease, chemotherapy may be necessary, and when no other treatment option is effective, a stem cell transplant may be considered. 

Who can treat SM?

Patients newly diagnosed with SM will likely be treated by a hematologist, dermatologist, immunologist and gastroenterologist.

What is the prognosis?

The prognosis depends on the type of SM that a patient has. 

Patients with indolent SM, which is the most common sub-type of the disease, have a normal life expectancy, while patients with mast cell leukemia, the most severe form of the disease, have a shortened life expectancy.

As a whole, the life expectancy of patients with SM is shorter than those of healthy people.