Systemic mastocytosis (SM) is a chronic, progressive disease with symptoms that gradually worsen over time. Mast cell activity causes long-term damage to internal organs and connective tissue, leading to deterioration in function. Disease progression is tracked by monitoring the evolution of symptoms, performing regular medical tests (such as blood tests) and measuring the impact on quality of life.
The subtypes of SM
What is SM?
Systemic mastocytosis (SM) is a rare hematological disease characterized by mast cells that are overactive and accumulate in different parts of the body such as the bone marrow, liver, spleen, gastrointestinal tract and lymph nodes.
There are 5 different subtypes of SM, each with a distinct level of aggressiveness and long-term prognosis:
- Indolent SM (ISM): The most common subtype, with milder symptoms that affect primarily the skin and gastrointestinal tract. It often stays stable over a number of years.
- Smoldering SM (SSM): A slow progressing subtype with a more significant burden.
- Aggressive SM (ASM): This subtype progresses rapidly, leading to organ damage and a reduced life expectancy.
- SM with an associated hematologic neoplasm (SM-AHN): Patients with this subtype have a blood disorder as well as SM. It aggressively damages organs and reduces life expectancy.
- Mast cell leukemia (MCL): A rare, aggressive cancer, with a short life expectancy (typically two to six months).
Monitoring disease progression in SM
In many patients, symptoms remain stable for years. If symptoms are worsening or new symptoms appear, it may be the disease progressing to a new subtype.
Your health care team will conduct blood tests to:
- Check for anemia or thrombocytopenia (low platelet count) which could point to complications related to the bone marrow.
- Measure tryptase levels to monitor mast cell activity.
A liver enzyme test will assess liver function, and a gastrointestinal biopsy is useful to measure the mast cell activity. Imaging such as radiography, CT or MRI or PET/CT are also valuable in determining disease progression.
Read more about SM prognosis
Signs of progression in SM
Tracking your symptoms’ severity, duration and frequency in a symptom diary is the best way to monitor disease progression. It is important to build the habit of keeping a detailed description of your symptoms, and how they impact your overall physical and mental well-being and daily life. By being consistent, you will create a clear picture of how your disease is evolving.
Signs that your SM is progressing include:
- Anaphylaxis reactions that are more frequent and more severe
- Worsening symptoms of nausea, vomiting, abdominal pain or diarrhea
- Severe skin reactions that don’t heal
- Bone pain or injury that could indicate the onset of osteoporosis
- An enlarged liver or spleen that may present as swelling of the abdomen
- Unexplained weight loss
- Persistent fatigue and weakness
Disease progression requires a change in treatment to try to slow its evolution and better manage symptoms to reduce the associated pain and discomfort.
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