Introduction
Systemic mastocytosis (SM) is a rare haematological disorder characterised by the clonal accumulation of abnormal mast cells in the bone marrow and other extracutaneous organs. Its clinical presentation is highly variable, ranging from indolent disease with relatively limited symptoms to advanced forms associated with organ dysfunction. Recognising this variability is important for timely diagnosis and appropriate risk assessment.[1,2]
Why Can Systemic Mastocytosis Be Difficult to Diagnose?
Patients may present with recurrent flushing, unexplained anaphylaxis, gastrointestinal symptoms, osteoporosis or other nonspecific manifestations. Some patients do not have obvious skin lesions, which can make recognition more challenging.
Diagnosis requires integration of clinical findings with laboratory and pathological investigations. Serum tryptase, bone marrow morphology, immunophenotyping and molecular testing for activating KIT mutations can contribute to the diagnostic assessment. Findings must be interpreted against established classification criteria rather than in isolation.[1,2]
Key Considerations for Clinical Practice
1. Recognise suggestive clinical patterns
Recurrent unexplained anaphylaxis, persistent mediator-related symptoms and otherwise unexplained skeletal or gastrointestinal manifestations may warrant further evaluation.
2. Integrate laboratory and pathological findings
Serum tryptase can support the assessment, while bone marrow examination, mast cell immunophenotyping and KIT mutation analysis help establish the diagnosis.
3. Determine the disease subtype
Distinguishing indolent disease from advanced systemic mastocytosis is essential because prognosis, monitoring and treatment strategies differ.
4. Consider evolving targeted therapies
Treatment is individualised according to disease subtype, symptom burden and organ involvement. Targeted therapies, including KIT-directed tyrosine kinase inhibitors, have expanded treatment options for selected patients with advanced disease.[1]
Conclusion
Systemic mastocytosis illustrates the importance of combining clinical suspicion with specialised laboratory and pathological assessment in rare diseases. Accurate classification can help guide risk stratification, follow-up and appropriate treatment selection.
Clinical takeaway: In patients with suggestive but unexplained multisystem symptoms, considering systemic mastocytosis may help prevent diagnostic delays and support appropriate specialist evaluation.
References
1. Pardanani A. Systemic Mastocytosis in Adults: 2026 Update on Diagnosis, Risk Stratification and Management. American Journal of Hematology. 2026. DOI: 10.1002/ajh.70395.
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2. Rets A, et al. Diagnosing Systemic Mastocytosis: State of the Art. International Journal of Laboratory Hematology. 2026;48(3):551–560. DOI: 10.1111/ijlh.70011.
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