“Mast cell diseaseMast cell disease A group of conditions in which mast cells behave abnormally by building up in excess, releasing chemicals too easily or both. Includes mastocytosis, mast cell activation syndrome and hereditary alpha-tryptasemia.” is an umbrella term for conditions in which mast cells build up abnormally, are overly active or both.
What is a 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.?
Mast cells are specialized cells of the immune system that mediate inflammatory responses and allergic reactions. They are found in the body’s connective tissue.
There are a few main branches under the mast cell disease tree. Mastocytosis involves an abnormal buildup of mast cells; it’s divided into 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., which affects the skin, and systemic mastocytosis (SM), which affects internal organs. The other main branch is 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 (MCAS), which causes recurrent systemic symptoms when mast cells release excessive chemical mediators.
Mastocytosis and MCAS can overlap. A person with mastocytosis may also have recurrent mast cell activation episodes.
Because these processes can affect different tissues, symptoms vary widely from person to person.
Read more about what defines a mast cell disease
Symptoms by subtype
Cutaneous mastocytosis
Cutaneous mastocytosis occurs when abnormal mast cells accumulate in the skin. It can cause tan, brown or reddish-brown spots or bumps that itch, swell or blister. Blistering is more common in infants and young children.
Although mast cell buildup is limited to the skin, mediator release can still cause symptoms elsewhere.
Systemic mastocytosis
In SM, abnormal mast cells accumulate in internal organs, most often the bone marrow. Skin involvement is reported in about 70% of people with SM.
In 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., patients may experience symptoms related to mast cell mediator release, such as flushing, itching, diarrhea and anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis.. Bone pain and osteoporosis are also associated with SM. Severe symptoms can occur in nonadvanced SM without the mast cell-related organ damage associated with advanced disease.
In 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., mast cell buildup can damage organs. Signs may include low blood cell counts caused by bone marrow dysfunction, liver damage with fluid buildup in the abdomen or intestinal malabsorption with significant weight loss.
An enlarged liver, spleen or lymph nodes can also occur, but enlargement alone does not mean the disease is advanced.
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Mast cell activation syndrome
MCAS causes recurrent episodes resembling anaphylaxis that typically affect at least two body systems. It is defined by inappropriate mast cell activation and excessive release of chemical mediators rather than mast cell accumulation. Mast cell numbers may be normal.
Symptoms by body system
Symptoms that can occur across mast cell disorders include:
- Skin: Flushing, itching, hives or swelling.
- Gastrointestinal: Abdominal pain, cramping, diarrhea, nausea or vomiting.
- Cardiovascular: Rapid heartbeat, low blood pressure, dizziness or fainting.
- Respiratory: Nasal congestion, wheezing or shortness of breath.
- Bone: Bone pain, osteopenia (loss of bone density), osteoporosis or fractures. In some people, unexplained osteoporosis or a low-impact fracture could be one of the first signs of SM.
- Neurological and cognitive: Headaches, fatigue or cognitive difficulties, sometimes described as brain fog.
These symptoms are nonspecific and can occur in many other conditions, which can make diagnosis challenging.
Possible symptom triggers
Possible triggers in mast cell disease include temperature changes, alcohol, exercise, stress, insect stings and certain medications, including nonsteroidal anti-inflammatory drugs and opioids. Triggers vary, and some episodes have no clear cause.
When to seek immediate care
Call 911 for possible anaphylaxis. Use epinephrineEpinephrine Also called adrenaline, this hormone is used in emergency situations to reverse symptoms during a severe allergic reaction (anaphylaxis). right away if it has been prescribed. Anaphylaxis can occur without hives.
Warning signs include:
- Trouble breathing.
- Throat or tongue swelling.
- Severe dizziness.
- Fainting.
- Confusion.
- Collapse.
- A sudden blood pressure drop.
Tell your care team about new or worsening symptoms, including unexplained weight loss, frequent fainting, new bone pain or fractures.
How is SM different from other mast cell diseases?
Symptoms alone cannot distinguish SM from cutaneous mastocytosis, MCAS or other mast cell disorders.
Testing may include a baseline serum 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. level, a blood test for the KIT D816V mutation and a bone marrow biopsyBone marrow biopsy A procedure to collect a sample of bone marrow using a needle. Often used to examine the characteristics of mast cells and diagnose SM., which is often needed to diagnose SM.
When MCAS is suspected, doctors can compare a tryptase level taken during an episode with the person’s baseline and assess whether symptoms improve with treatments that block mast cell mediators.
