Brenton Mar, MD, PhD, Senior Medical Director at Blueprint Medicines, gives an overview of systemic mastocytosis (SM) and advanced SM.

SM is a rare, hematologic disorder most often caused by a mutation in the KIT D816V gene. The disorder is characterized by uncontrolled mast cell proliferation and activation across multiple organ systems, resulting in chronic, severe, and often unpredictable symptoms and extensive organ damage. A minority of SM patients have advanced SM, which encompasses a group of high-risk SM subtypes including aggressive systemic mastocytosis (ASM), systemic mastocytosis with an associated hematological neoplasm (SM-AHN), and mast cell leukemia (MCL).
As Dr. Mar explains, the diagnostic journey for SM patients is often long, especially for those who do not have an advanced form of the disease for which diagnosis can take 7 years. Even in advanced SM, diagnosis can take up to 2 years. Since advanced SM is often life-threatening, non-diagnosis can be fatal.

SM-AHN is the most common form of advanced SM which means advanced SM patients often have another hematologic disorder. As Dr. Mar explains, this can lead to problems when trying to diagnose these patients because the symptoms of the associated hematologic neoplasm may mask the signs of SM.

Finally, Dr. Mar describes signs of SM that physicians can look out for. Urticaria pigmentosa is the most common symptom though severe weight loss and refractory ascites may also suggest SM. Additionally, with the advent of next-generation sequencing, a mutation in the KIT D816V gene may also indicate SM.

To learn more about SM and other rare hematologic disorders, visit checkrare.com/diseases/hematologic-disorders/