What Is Systemic Mastocytosis?

Systemic Mastocytosis (SM) is a rare and chronic disorder characterized by an excessive accumulation of mast cells in various organs of the body. Mast cells are a type of white blood cell that play a crucial role in the body's immune system. They are involved in allergic reactions and help to fight off certain diseases. In SM, these cells multiply abnormally and accumulate in different parts of the body, including the skin, bone marrow, liver, spleen, and gastrointestinal tract. This can lead to a range of symptoms, including: skin lesions, abdominal pain, peptic ulcers, diarrhea, and anaphylaxis.

Types of Systemic Mastocytosis

There are several types of Systemic Mastocytosis, which are classified based on the severity of the disease and the organs involved. These include:

Indolent Systemic Mastocytosis (ISM): This is the most common type and is typically less severe. Patients with ISM may experience symptoms such as skin lesions, flushing, and gastrointestinal problems.
Systemic Mastocytosis with an Associated Hematologic Neoplasm (SM-AHN): In this type, patients have Systemic Mastocytosis along with another blood disorder.
Aggressive Systemic Mastocytosis (ASM): This is a more severe form of the disease, where mast cells infiltrate and damage vital organs.
Mast Cell Leukemia (MCL): This is the most severe form of Systemic Mastocytosis, where mast cells make up more than 20% of the cells in the blood or bone marrow.

Why do people get Systemic Mastocytosis?

The exact cause of SM is not fully understood. However, it is known to be associated with mutations in the KIT gene. This gene provides instructions for making a protein that is involved in the growth, division, and survival of cells. Mutations in the KIT gene lead to uncontrolled growth and accumulation of mast cells. While some people with SM have a family history of the disease, most cases are sporadic, meaning they occur in people with no history of the disorder in their family.

Who gets Systemic Mastocytosis?

SM is a rare disease affecting approximately 32,000 patients in the U.S. (or 0.01% of the population). Systemic Mastocytosis is not a condition that is passed down in families. The mutation KIT D8I6V causes approximately 95% of SM cases. It is not considered an autoimmune disease.

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Types of Systemic Mastocytosis

There are several types of Systemic Mastocytosis, which are classified based on the severity of the disease and the organs involved. These include:

Indolent Systemic Mastocytosis (ISM): This is the most common type and is typically less severe. Patients with ISM may experience symptoms such as skin lesions, flushing, and gastrointestinal problems.
Systemic Mastocytosis with an Associated Hematologic Neoplasm (SM-AHN): In this type, patients have Systemic Mastocytosis along with another blood disorder.
Aggressive Systemic Mastocytosis (ASM): This is a more severe form of the disease, where mast cells infiltrate and damage vital organs.
Mast Cell Leukemia (MCL): This is the most severe form of Systemic Mastocytosis, where mast cells make up more than 20% of the cells in the blood or bone marrow.