Glossary

In these subtypes of SM, mast cells begin to damage organs. Advanced SMAdvanced SM In these subtypes of SM, mast cells begin to damage organs. Advanced SM includes the subtypes aggressive SM, mast cell leukemia and SM with an associated hematological neoplasm. includes the subtypes aggressive SMAggressive SM A subtype of advanced SM marked by a high mast cell burden that leads to organ damage. Aggressive SM accounts for less than 10% of SM cases., mast cell leukemiaMast cell leukemia The most severe subtype of SM, caused by the rapid buildup of immature mast cells in the bone marrow and blood. Mast cell leukemia accounts for less than 5% of SM cases and has a poor prognosis. and SM with an associated hematological neoplasmSM with an associated hematological neoplasm A form of advanced SM and the second-most common subtype of SM overall. In this subtype, SM occurs alongside another blood disorder. Also called SM with an associated myeloid neoplasm..

A subtype of advanced SMAdvanced SM In these subtypes of SM, mast cells begin to damage organs. Advanced SM includes the subtypes aggressive SM, mast cell leukemia and SM with an associated hematological neoplasm. marked by a high mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. burden that leads to organ damage. Aggressive SMAggressive SM A subtype of advanced SM marked by a high mast cell burden that leads to organ damage. Aggressive SM accounts for less than 10% of SM cases. accounts for less than 10% of SM cases.

A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis..

Medications that block the effects of histamineHistamine A chemical released by mast cells when they are activated. Histamine causes many of the allergy-type symptoms in mastocytosis, including flushing, itching and hives., the chemical found in mast cells that is responsible for many of the symptoms of SM, as well as many allergic reactions.

A procedure to collect a sample of bone marrow using a needle. Often used to examine the characteristics of mast cells and diagnose SM.

A subtype of indolent SMIndolent SM A subtype of nonadvanced SM caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SM accounts for around 90% of SM cases. that occurs when the excess mast cells accumulate in the bone marrow, but not the skin or other organs.

Also called adrenaline, this hormone is used in emergency situations to reverse symptoms during a severe allergic reaction (anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis.).

A chemical released by mast cells when they are activated. HistamineHistamine A chemical released by mast cells when they are activated. Histamine causes many of the allergy-type symptoms in mastocytosis, including flushing, itching and hives. causes many of the allergy-type symptoms in mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults., including flushing, itching and hives.

A subtype of nonadvanced SMNonadvanced SM In these subtypes of SM, mast cells accumulate in the body but do not usually cause severe organ damage. Nonadvanced SM includes the subtypes indolent SM and smoldering SM. caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SMIndolent SM A subtype of nonadvanced SM caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SM accounts for around 90% of SM cases. accounts for around 90% of SM cases.

Most SM cases are caused by the KIT D816V mutation. The KIT gene codes for a type of protein called a receptor tyrosine kinase, which signals mast cells to grow, divide and move.

A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body.

Describes when mast cells release histamineHistamine A chemical released by mast cells when they are activated. Histamine causes many of the allergy-type symptoms in mastocytosis, including flushing, itching and hives. and other mediators into the blood stream in response to an allergen or other trigger. This leads to symptoms like fatigue, rash and, in severe cases, anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis..

A group of conditions in which mast cells behave abnormally by building up in excess, releasing chemicals too easily or both. Includes mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults., mast cell activationMast cell activation Describes when mast cells release histamine and other mediators into the blood stream in response to an allergen or other trigger. This leads to symptoms like fatigue, rash and, in severe cases, anaphylaxis. syndrome and hereditary alpha-tryptasemia.

The most severe subtype of SM, caused by the rapid buildup of immature mast cells in the bone marrow and blood. Mast cell leukemiaMast cell leukemia The most severe subtype of SM, caused by the rapid buildup of immature mast cells in the bone marrow and blood. Mast cell leukemia accounts for less than 5% of SM cases and has a poor prognosis. accounts for less than 5% of SM cases and has a poor prognosis.

Medications such as cromolyn sodium that prevent mast cells from releasing histamineHistamine A chemical released by mast cells when they are activated. Histamine causes many of the allergy-type symptoms in mastocytosis, including flushing, itching and hives. and other chemicals that cause symptoms.

Rare disease caused by the buildup of mast cells. Cutaneous mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults. primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults.

SM used to be classified as a type of myeloproliferative neoplasmMyeloproliferative neoplasm SM used to be classified as a type of myeloproliferative neoplasm, a group of rare blood cancers characterized by an overaccumulation of blood cells in the bone marrow., a group of rare blood cancers characterized by an overaccumulation of blood cells in the bone marrow.

In these subtypes of SM, mast cells accumulate in the body but do not usually cause severe organ damage. Nonadvanced SMNonadvanced SM In these subtypes of SM, mast cells accumulate in the body but do not usually cause severe organ damage. Nonadvanced SM includes the subtypes indolent SM and smoldering SM. includes the subtypes indolent SMIndolent SM A subtype of nonadvanced SM caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SM accounts for around 90% of SM cases. and smoldering SMSmoldering SM A subtype of nonadvanced SM, with a higher mast cell burden than the indolent subtype. Smoldering SM has a higher likelihood of progressing to an advanced form..

A form of advanced SMAdvanced SM In these subtypes of SM, mast cells begin to damage organs. Advanced SM includes the subtypes aggressive SM, mast cell leukemia and SM with an associated hematological neoplasm. and the second-most common subtype of SM overall. In this subtype, SM occurs alongside another blood disorder. Also called SM with an associated myeloid neoplasm.

A subtype of nonadvanced SMNonadvanced SM In these subtypes of SM, mast cells accumulate in the body but do not usually cause severe organ damage. Nonadvanced SM includes the subtypes indolent SM and smoldering SM., with a higher mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. burden than the indolent subtype. Smoldering SMSmoldering SM A subtype of nonadvanced SM, with a higher mast cell burden than the indolent subtype. Smoldering SM has a higher likelihood of progressing to an advanced form. has a higher likelihood of progressing to an advanced form.

The symptoms of SM may become worse when certain triggers activate mast cells. Common symptom triggers in SM include exercise, insect bites, stress, scented products, alcohol and spicy foods.

A rare, chronic blood disease where too many mast cells build up in the body, especially in organs that are directly exposed to the environment, such as the skin and digestive system.

A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptaseTryptase A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptase are a key indicator of SM. are a key indicator of SM.

Targeted therapies designed to block the KIT D816V mutation that drives most cases of SM. Includes avapritinib, midostaurin and imatinib.

A skin condition marked by itchy, red-to-brown spots, especially on the neck, limbs and torso. It is caused by surplus mast cells and occurs in up to 85% of patients with SM.