Advances in the Management of Mediator-Related Symptoms in Non-Advanced Systemic Mastocytosis.

Systemic mastocytosis (SM) is a rarely occurring clonal mast-cell disorder defined by aberrant mast-cell accumulation and episodic or chronic mediator release, giving rise to a broad range of manifestations from pruritus and flushing to gastrointestinal symptoms and anaphylaxis. In non-advanced SM, mediator-related symptoms are the major source of morbidity and substantially impair quality of life. Traditional symptom-directed therapies-including antihistamines, leukotriene modifiers, and mast-cell stabilizers-remain the foundation of care, but a subset of patients experience persistent, refractory symptoms. Advances in mast-cell biology have expanded therapeutic options for these patients, including selective KIT inhibitors, mast-cell--modulating small molecules, inhibitory-receptor agonists, epithelial-derived cytokine blockade, and agents targeting IgE-dependent and IgE-independent activation pathways. Key gaps remain, including the absence of validated biomarkers that distinguish activation from mast-cell burden, limited long-term safety data, and uncertainty around optimal dosing strategies. This review summarizes current understanding of mediator-driven disease in non-advanced SM and highlights targeted, mechanism-based therapies for refractory symptoms.