Mastocytosis: Diagnosis and Treatment

Mastocytosis is a neoplastic disorder driven by activating mutations of the KIT receptor tyrosine kinase that produce clonal proliferation of mast cells. It is classified as cutaneous mastocytosis (limited to the skin and most often seen in children) or systemic mastocytosis (with bone marrow and/or other organ involvement, typically in adults).

The KIT D816V mutation is detected in over 90 percent of patients with systemic mastocytosis. Serum tryptase is the key biomarker for monitoring disease burden. The clinical picture comprises skin lesions such as urticaria pigmentosa, mast cell mediator-release symptoms (flushing, diarrhea, anaphylaxis), and findings of organ infiltration.

In indolent systemic mastocytosis, control of mediator-release symptoms with antihistamines and mast cell stabilizers is the primary approach. In advanced systemic mastocytosis (aggressive SM, mast cell leukemia), avapritinib, a selective inhibitor of KIT D816V, is the FDA-approved targeted therapy. Midostaurin is also used in advanced mastocytosis.