Systemic Mastocytosis (SM): Symptoms and Testing

What is Systemic Mastocytosis (SM)?

• Systemic mastocytosis (SM) is a group of rare blood diseases, where too many abnormal mast cells, which are specialized immune cells, grow and accumulate in the body^1,2.
  • Organs affected by mast cell buildup may include the skin, liver, spleen, bone marrow, and organs of the gastrointestinal tract^1,3.
• Mast cells are produced in the bone marrow and found in connective tissues all over the body. They release multiple chemical mediators, such as histamine, tryptase, heparin and other inflammatory substances. These mediators are released as part of allergic and inflammatory reactions^4,5.
  • In healthy people, mast cells help protect the body from infection and defend it from other harmful substances².
  • The accumulation of abnormal mast cells seen in SM leads to the release of higher levels of mast cell mediators and generalized inflammation in the body, causing a range of symptoms. These can include flushing of the skin, headaches, digestive problems, extreme allergic reactions, bone pain, and fatigue^2,3.
• Very serious cases of SM can lead to organ damage or even organ failure³.
• Early identification of the disease by a health care provider can be critical as there are several different subtypes of SM and each varies in severity and life expectancy^3,6,7,8. It is important for patients to work closely with a health care provider to develop a treatment plan.

Do I Have SM?

• You may have SM if you have a history of persisting symptoms that remain undiagnosed or misdiagnosed, including itching, abdominal pain, anemia, nausea, diarrhea, vomiting and anaphylaxis, a severe allergic reaction. A confirmed diagnosis of SM can only be verified by a bone marrow biopsy and a blood test^3,9.
• SM is a difficult disease to identify because its symptoms can be confused with those related to other diseases that health care professionals see more regularly¹⁰. Many people do not receive a proper diagnosis for 2 to 10 years after they first see symptoms⁶. 
• People with SM are frequently underdiagnosed or misdiagnosed with other conditions, such as irritable bowel syndrome or malabsorption syndrome⁸. Also, those diagnosed with a blood cancer such as leukemia could also have a mast cell disorder¹¹.
• Before they are correctly diagnosed, people with SM are likely to be referred to several different health care professionals, including dermatologists, allergists, hematologists gastroenterologists, endocrinologists, internal medicine specialists, rheumatologists, cardiologists, and neurologists¹². 
• SM can impact a person’s mental health. People with SM are at risk for depression, anxiety, poor motivation, or increased stress¹³. Anyone experiencing mental health problems should seek support and counseling from a health care professional.
• If the presence of SM is suspected, talk to a health care provider about SM testing early to confirm a diagnosis. Treatment may be needed once a diagnosis is confirmed, and a comprehensive care plan with follow-up can ease the physical and emotional impact of living with the disease.
   

Testing for SM

If SM is suspected, patients should talk to a health care provider about tests that may help identify the disease³. As SM is an extremely rare disease, physicians may not be familiar with testing or diagnosing it^1,6. Diagnosis can only be confirmed by the following tests: 

• Blood tests, which identify abnormalities in the blood, help physicians diagnose SM:
  • Blood serum tryptase test: Serum tryptase is an enzyme, or chemical, released by mast cells⁴. Testing for elevated serum tryptase can help diagnose the disease, because a person who has SM is likely to have significantly higher levels of this enzyme³.
  • Blood serum albumin test: A serum albumin test is a blood test that measures the amount of albumin in the patient’s blood. Low levels of albumin are often associated with inflammation in the liver and malnutrition¹⁴.
  • Alkaline phosphatase (ALP) test: The test measures the amount of ALP enzyme in the bloodstream. If ALP levels are elevated, it indicates a problem with the liver or bones¹⁵.
  • Hemoglobin test: Anemia, a condition in which the blood has fewer red blood cells than normal, can be a sign of SM^3,16. A hemoglobin test is used to check for anemia¹⁷.
  • Complete Blood Count (CBC): Low blood platelet count (thrombocytopenia), and high white blood cell count (leukocytosis) can be signs of advanced variants of SM^3,18. CBC tests measure many different parts of the blood, including the overall number of white blood cells and platelets¹⁷.
  • Genetic mutation testing:  Learning if a genetic mutation is present can help physicians diagnose SM³. A mutation is a change in a gene’s structure³. Mutations in a gene known as KIT often cause uncontrolled growth of mast cells¹⁹. KIT D816V is the most common KIT mutation, occurring in approximately 9 out of 10 SM patients, which makes it a key tool for diagnosis^3,20.  
• CT Scanning and other imaging: Infiltration of abdominal organs and lymph nodes can best be seen by a variety of CT and other scans²².
• Biopsies: Procedures performed using a biopsy needle, to extract samples of the organ for evaluation²¹. They are vital in diagnosing SM^3,22:
  • Bone marrow biopsy: To confirm the overproduction of mast cells in bone marrow or other organs, a physician can test a patient’s bone marrow to see if it contains too many mast cells. This test can also give information about the SM subtype³.

Download the fact sheet (PDF 0.6 MB)

A Closer Look at the Five Types of SM⁷

SM-AHN, ASM, and MCL are all defined as Advanced SM and have lower survival rates when compared to ISM and SSM^8,18.

For more information and resources, visit No Disease Too Small (www.nodiseasetoosmall.com)
The Mastocytosis Society* may be another source of information for you: www.tmsforacure.org