Systemic Mastocytosis: Prevalence, Classification, and Pathophysiology

Welcome back to another Dermatology Times Case-Based Peer Perspectives series. In this episode titled, ‘Systemic Mastocytosis: Prevalence, Classification, and Pathophysiology’, the expert dermatologist leads the conversation about the following questions:

How common is systemic mastocytosis (SM), and why might it be underdiagnosed or more prevalent than current estimates suggest?

Can you please briefly describe the subtypes of SM, including nonadvanced and advanced forms?

How do the WHO diagnostic criteria support this classification?

What is the underlying pathogenesis of systemic mastocytosis, and how does the KIT D816V mutation contribute to mast-cell proliferation and activation?

How prevalent is the KIT D816V mutation in SM overall, and in indolent SM specifically?

Dr. Lauren Madigan explains that SM is a rare clonal hematologic disorder occurring in approximately 1 in 10,000 people, with 88–95% of cases classified as non-advanced subtypes like indolent or smoldering SM. She highlighted that while the disease is often underdiagnosed due to nonspecific gastrointestinal and neurocognitive symptoms, dermatologists are uniquely positioned to identify it through biopsies of fixed skin lesions. The pathogenesis is primarily driven by the KIT D816V gain-of-function mutation, which is present in roughly 95% of non-advanced patients and leads to the constitutive proliferation and accumulation of mast cells in various organs. Dr. Madigan distinguishes between disease severities using "B findings" (high mast cell burden) and "C findings" (true organ dysfunction), noting that while skin involvement is nearly universal in indolent cases, it still appears in 30–50% of advanced subtypes.

In the next episode, ‘Diagnosis and Treatment of Systemic Mastocytosis in Dermatology’, Dr. Madigan will continue her discussion on SM and highlight the clinical presentation and multidisciplinary management of SM, emphasizing the challenges of diagnostic delays and the necessity of tailored care. Dr. Madigan will highlight how various specialists collaborate to address the diverse symptoms and complications associated with the disease.