Systemic mastocytosis

Systemic mastocytosis is a heterogeneous group of disorders, especially in European adults, caused by too many mast cells in the body. The genetic basis of the disease is a mutation in the growth receptor KIT, which leads to an uncontrolled activation of the receptor.

Mainly people of European descent in adulthood are affected. A distinction is made between the indolent SM (ISM) and the aggressive SM (ASM). In both forms, the mast cells accumulate in the bone marrow, more rarely in the liver, spleen, gastrointestinal tract, or lymph nodes. The disease occurs without skin involvement. 

Symptoms are primarily caused by the release of the substances stored in the mast cells (mediators, cytokines or histamine, leukotrienes, prostaglandins and heparin). Triggers include e.g. alcohol, spicy food, food supplements, stress, certain medications (morphine derivatives, anesthetics, codeine, local anesthetics, quinine, aspirin), insect venoms, allergic reactions, and physical triggers (exertion, sunlight, cold, heat, friction).

There is an increased risk for the development of another hematological neoplasm. It is suspected that a high number of unreported cases exist, which can often be misdiagnosed as chronic gastrointestinal discomfort.

There are several different forms of the disease, these including:

- Indolent systemic mastocytosis (ISM)
- Isolated bone marrow mastocytosis (BMM)
- Smoldering systemic mastocytosis (SSM)
- Systemic mastocytosis with concomitant blood disease (SM-AHNMD)
- Aggressive systemic mastocytosis (ASM)
- Mast cell leukemia (MCL)
- Mast cell sarcoma
- Extracutaneous mastocytoma