If you have recently been diagnosed with systemic mastocytosis (SM), you may feel a strange relief that your symptoms finally have a name. But that relief might be quickly followed by a harder question: Can you cure it?
There is no standard cure for 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., or any other form of 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.. For most people that reality isn’t as bleak as it might sound, though, because medications, trigger avoidance and supportive care now go a long way towards managing the disease.
Different types, different story
Mastocytosis is not one disease; it has many forms. How treatable it is, and how much it might affect your daily life, depends on the specific type you have.
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When abnormal mast cells build up only in the skin, the condition is called cutaneous mastocytosis; when they collect in internal organs such as the bone marrow, it is called systemic mastocytosis.
In children, the cutaneous form usually resolves by the end of puberty. In adults, it is highly likely to progress to SM.
SM is divided into several subtypes that fall into two broad groups:
- 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.. This includes several forms, most commonly 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. (ISM) 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. (SSM). Mast cells accumulate and can cause uncomfortable 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. symptoms, flushing, itching, digestive upset, headaches, fatigue and even anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis.. However, nonadvanced SM rarely damage organs, and most people live a normal lifespan.
- 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.. Much rarer and more serious, this group covers 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. (ASM), SM alongside blood cancer (SM-AHN), and 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. (MCL). Here mast cells can damage organs, causing an enlarged liver or spleen, lowering blood counts, weakening bones or causing weight loss from the malabsorption of nutrients. In advanced SM, the disease is more likely to shorten life.
Read more about SM prognosis: “How long can you live with systemic mastocytosis?”
Symptom management versus targeted therapies
Your specific subtype of mastocytosis will largely guide the treatment your care team offers. Treatment can be divided into two broad approaches:
- Symptom management. Here, antihistamines are the mainstay — H1 blockers ease flushing, itching, and hives, while H2 blockers calm gut symptoms. These are used alongside other medicines like mast cell stabilizers, leukotriene blockers and topical corticosteroid creams for the skin.
- Targeted therapies. These target the faulty signals that drive the disease, rather than just easing symptoms. Most SM is driven by a mutation in the KIT gene, and specific KIT inhibitors block it. Avapritinib is approved for indolent SM with troublesome symptoms; for advanced SM, midostaurin and avapritinib can slow the disease and improve quality of life.
Whatever your subtype, anyone at risk of anaphylaxis usually carries an epinephrine auto-injector.
The one potential cure for mastocytosis
Mast cells, like other blood cells, form from stem cells in the bone marrow. Therefore, one treatment can potentially cure systemic mastocytosis: an allogeneic hematopoietic cell transplant.
In this stem cell transplant procedure, strong chemotherapy is used to wipe out your body’s blood-forming cells. Then, they are replaced with healthy stem cells from a donor. The hope is that the donor cells will begin making healthy blood cells for the body.
Hematopoietic stem cell transplantation carries serious life-threatening risks, such as infection or the body rejecting the donor cells. It’s therefore only used in advanced SM, and only selectively. Even within these advanced forms of SM, recent research shows a transplant does not always help all patients equally. KIT inhibitors still serve a purpose here, as taking them prior to the procedure can improve both your fitness for it and your survival afterward.
