Learn The BasicsThere are different therapies available for patients with systemic mastocytosis (SM) based on the individual symptoms and disease subtype of each patient.
While some therapies are non-specific and generalized for any type of allergic reaction, others specifically target SM.
Antihistamines
Antihistamines work by blocking the effects of histamine, the chemical found in mast cells that are responsible for many of the symptoms of SM, as well as many allergic reactions.
H1 and H2 antihistamines should be used for the initial pharmacological treatment of SM. H1 antihistamines can help prevent flushing and itching, while H2 antihistamines can reduce abdominal pain, heartburn, cramping and diarrhea.
Epinephrine
Patients with SM should also carry epinephrine with them at all times to treat episodes of anaphylaxis (a severe and potentially life-threatening allergic reaction) or low blood pressure.
Epinephrine is a hormone that is normally made by the adrenal glands—small glands found on top of the kidneys that produce many of the hormones that regulate different systems in the body. It is often used to treat allergic reactions, and it can be administered outside of a doctor’s office.
Omalizumab
Omalizumab is an antibody against immunoglobulin E (IgE), which is produced by the body during an allergic reaction. It works by hindering the binding of IgE to mast cells. This way, it may reduce the frequency of anaphylaxis and can be beneficial in some patients with SM.
Glucocorticoids
Glucocorticoids are a class of steroid hormones that are also produced by the adrenal glands. They play a key role in the metabolism of glucose, protein and fat in the body.
Oral glucocorticoids may be beneficial in patients with aggressive SM. Maintenance therapy with low-dose glucocorticoid may also be considered as a second-line therapy in patients with SM who do not respond to antihistamines or omalizumab.
Interferon alpha
Cases of advanced SM may also be treated with non-targeted agents that inhibit the proliferation of mast cells, such as interferon alpha, a cell signaling molecule that is produced by the immune system in response to environmental agents. Different formulations of interferon-alpha have been developed to treat diseases including cancer.
Cladribine
Another second-line approach that may be considered in treating patients with SM who do not respond to first-line therapy is cladribine, an agent that can be used to reduce the number of mast cells, which are overactive in the case of SM.
Cladribine can also be used to manage aggressive forms of SM.
Tyrosine kinase inhibitors
Most cases of SM are caused by a mutation in a gene called KIT, which codes for a protein called CD117, a transmembrane tyrosine kinase. This protein helps in the growth and migration of mast cells.
Tyrosine kinase inhibitors such as avapritinib and midostaurin can be used to treat patients with SM who do not respond to other therapies, depending on their KIT mutation status.
Avapritinib, sold under the brand name Ayvakit, has been approved in the United States and European Union for the treatment of advanced systemic mastocytosis.
Midostaurin, sold under the brand names Rydapt and Tauritmo, can be used to treat aggressive SM, SM with associated hematologic neoplasm and mast cell leukemia.
