Mariana C. Castells MD, PhD, Division of Allergy and Clinical Immunology, Brigham and Women’s Hospital, and Professor of Medicine, Harvard Medical School, gives an overview of mastocytosis.

As Dr. Castells explains, mastocytosis 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. 

There are a number of mastocytosis subtypes, including cutaneous mastocytosis and systemic mastocytosis. The former primarily affects children and primarily involves the skin. In systemic mastocytosis, pathologic accumulation of mast cells is evident in tissue(s) other than skin – most commonly in bone marrow. Indolent systemic mastocytosis is generally associated with low mast cell burden and presence of mediator-related symptoms. Most patients with indolent systemic mastocytosis also have maculopapular skin lesions. Some patients may present with an enlarged liver or spleen and the gastrointestinal tract may also be affected. Life expectancy in patients with indolent systemic mastocytosis is comparable to the general population.

Recently, the results of TouchStone, a patient and healthcare provider (HCP) study on the burden and needs of patients living with systemic mastocytosis, were published in two papers titled “Patient-reported Outcomes Among Patients with Systemic Mastocytosis in Routine Clinical Practice: Results of the TouchStone SM Patient Survey” and “Perceptions of Patient Disease Burden and Management Approaches in Systemic Mastocytosis: Results of the TouchStone Healthcare Provider Survey.” 

To learn more about systemic mastocytosis and other rare hematologic disorders, visit