Systemic mastocytosis (SM) is a rare disorder characterized by the abnormal accumulation of mast cells in various tissues throughout the body. Mast cells are a type of white blood cell that are released during allergic reactions; in SM, there is an overproduction of these mast cells. SM effects an estimated 1 in 10,000 people globally 1 and while around 75-90% of people with SM have indolent systemic mastocytosis (ISM), SM can also progress to advanced stages, called advanced systemic mastocytosis (AdvSM).2,3 AdvSM includes three subtypes: aggressive systemic mastocytosis (ASM), systemic mastocytosis with associated hematologic neoplasms (SM-AHN), and mast cell leukemia (MCL).2 Some patients may also develop smoldering systemic mastocytosis, a moderate form of disease with similar symptoms to ISM, but more widespread organ involvement.2 Understanding the signs and symptoms of SM and its subtypes is crucial for timely diagnosis and appropriate management.
Differentiating ISM and AdvSM
ISM involves the accumulation of mast cells primarily in the bone marrow and other organs such as the skin, liver, spleen, and stomach. These mast cells release inflammatory mediators like histamine, leading to symptoms that are similar to those occurring in allergic reactions. This includes pruritis, urticaria, and sometimes even anaphylaxis. Because mast cells can also infiltrate the gastrointestinal tract, patients may present with diarrhea, nausea, and abdominal pain.4,5
AdvSM is the result of uncontrollable mast cell proliferation that causes widespread tissue damage, particularly in the liver, spleen, and bone marrow. This may result in hepatosplenomegaly, anemia, leukopenia, thrombocytopenia, and significant fatigue. Patients also often experience more debilitating gastrointestinal symptoms than those with ISM.4,5
Looking ahead to symptom control
ISM is typically slowly progressing and does not significantly affect life expectancy. Treatment focuses on symptom management based on involved organ systems.6 AdvSM is more aggressive than ISM and can result in organ failure and a poor prognosis if not treated effectively. Chemotherapy or other systemic treatments may be required in some cases. Recent pharmacological advancements have resulted in the first Food and Drug Administration (FDA) approved medication to treat ISM and AdvSM, providing hope for affected patients and their families.3
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