Systemic mastocytosis with an associated hematological neoplasm (SM-AHN) is an advanced subtype of SM. In SM-AHN, patients have both SM and an associated blood malignancy (in layman’s terms, “hematological neoplasm” means a blood-related cancer).
What characterizes SM-AHN?
One in five patients with SM have SM-AHN. It’s the most common 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., accounting for 70% of advanced SM cases. SM-AHN is more common among older individuals.
The SM portion of the disease usually falls under the category 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., but it can also appear as aggressive SM or mast cell leukemia. When it appears as indolent SM, it can cause symptoms like urticaria pigmentosa, gastrointestinal issues and headaches.
Various types of blood malignancies can cause the AHN portion of the disease, but the blood cancers most frequently observed in SM-AHN are myeloproliferative neoplasms (MPNs), when the bone marrow makes too many blood cells, and chronic myelomonocytic leukemia (CMML), when the body makes too many monocytes, a type of white blood cell.
How is SM-AHN diagnosed?
A diagnosis of SM-AHN means identifying both the SM and AHN component. This can be difficult since their signs and symptoms may overlap, especially when it comes to categorizing the specific subtype of SM. The AHN may also hide the signs of the SM component.
The SM diagnosis can only be confirmed after laboratory testing has been carried out, including a process in which doctors extract a sample of your bone marrow to analyze it for the abnormal accumulation of mast cells. After a diagnosis of SM has been established, doctors will look for further evidence regarding the nature and severity of the disease to understand its subtype. This includes looking at all the organs possibly affected in SM, such as the spleen and liver.
What is the clinical course and prognosis of SM-AHN?
SM-AHN is one of three advanced subtypes of SM. It is associated with an aggressive clinical course compared with milder SM subtypes, such as indolent 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..
Generally, the prognosis of SM-AHN depends largely on the specific AHN component. For example, patients with CMML typically have a shorter survival period compared with patients with the MPN cancer subtype (15 months versus 31 months). For SM-AHN overall, the median survival is 24 months.
Read more about SM treatment and care
How is SM-AHN treated?
Treating SM-AHN usually means treating both the SM and AHN components.
For the SM component of the disease, doctors typically administer therapies to reduce the symptoms related to overactive mast cells. This may include antihistaminesAntihistamines Medications that block the effects of histamine, the chemical found in mast cells that is responsible for many of the symptoms of SM, as well as many allergic reactions., which are used to address allergic reactions, and corticosteroids, which are used to reduce inflammation.
Midostaurin and avapritinib are sometimes administered if there is a genetic basis for their use. These drugs are known as KIT inhibitors and are effective in patients who have a KIT mutation.
For the blood cancer component of the disease, chemotherapy and immunotherapy are often necessary. Some patients may be good candidates for stem cell transplantation. Treatment varies between patients because it is typically tailored towards individual needs and takes into account both the severity and aggressiveness of the cancer. Doctors also adjust treatment based on clinical responses. Therefore, there is no “one size fits all” approach to the management of SM-AHN, with outcomes varying based on the therapies needed, the therapies available and the clinical responses achieved.
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