Systemic Mastocytosis in Adults: 2026 Update on Diagnosis, Risk Stratification and Management.
1Division of Hematology, Department of Medicine, Mayo Clinic, Rochester, Minnesota, USA.
American Journal of Hematology
|June 18, 2026
Summary
Systemic mastocytosis (SM) involves abnormal mast cell growth. Diagnosis relies on bone marrow clusters and specific markers, guiding treatment from symptom management in indolent forms to cytoreductive therapies and targeted inhibitors in advanced disease.
Area of Science:
- Hematology
- Oncology
- Pathology
Background:
- Systemic mastocytosis (SM) is characterized by the clonal proliferation of mast cells (MC) in organs outside the skin.
- Diagnosis involves identifying multifocal MC clusters in bone marrow or other organs, alongside elevated serum tryptase, specific MC marker expression, and KIT mutations.
Purpose of the Study:
- To outline the diagnostic criteria for systemic mastocytosis.
- To detail the classification of SM into indolent and advanced subtypes.
- To review current management strategies based on disease subtype and risk stratification.
Main Methods:
- Diagnosis relies on major criteria (multifocal MC clusters) and minor criteria (serum tryptase, MC markers, KIT mutations).
- Subtyping follows International Consensus Classification/WHO guidelines, differentiating indolent/smoldering SM (ISM/SSM) from advanced SM (ASM, SM-AMN, mast cell leukemia).
- Risk stratification incorporates poor-risk mutations (ASXL1, RUNX1, SRSF2, NRAS) and established prognostic models.
Main Results:
- Treatment for ISM focuses on symptom control, anaphylaxis prevention, and osteoporosis management.
- Advanced SM requires cytoreductive therapy to address organ dysfunction, with tyrosine kinase inhibitors (TKIs) like midostaurin and avapritinib transforming treatment.
- Avapritinib shows promise but its efficacy in complex SM-AMN cases is under investigation; cladribine aids MC debulking, while interferon-α has a reduced role. SM-AMN treatment targets the myeloid component, potentially involving stem cell transplant.
Conclusions:
- Accurate SM subtyping and risk stratification are crucial for effective management.
- TKIs represent a significant advancement in SM therapy, particularly for advanced disease.
- Treatment approaches are tailored to the specific SM subtype and patient risk profile, with ongoing research into novel therapies.
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