I am KIT D816V—the hidden mutation causing systemic mastocytosis (SM). I can evade low-sensitivity testing, and delay diagnosis from symptom onset.1-3,12,19
Each specialist in a patient’s diagnostic journey has the opportunity to identify and confirm the presence of KIT D816V. The key is to look out for the various symptoms of systemic mastocytosis and pursue an accurate mutational assay.12,19
When patients present with systemic mastocytosis symptoms in the areas of skin, gastrointestinal, respiratory, systemic, cardiovascular, neuropsychiatric, or musculoskeletal systems, be sure to run a tryptase test. The level will help direct you to the appropriate next steps.5,34
The measurement of serum tryptase is a diagnostic approach that can be used as a diagnostic marker in systemic mastocytosis, and help distinguish between categories of the disease.35 When serum total tryptase persistently exceeds 20 ng/mL (a WHO minor criterion), results should be interpreted alongside full clinical and lab findings.5,35,a
Mastocytosis unlikely, but cannot be ruled out5,36
Systemic mastocytosis possible– screen for KIT D816V in peripheral blood with high-sensitivity assay5
Bone marrow biopsy and screen for KIT D816V mutation5
For ~95% of systemic mastocytosis patients, the KIT D816V mutation drives their mastocytosis.1 Low-sensitivity assays may fail to detect the mutation and potentially prolong the search for a diagnosis.12
NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) recommend34:
Bone marrow is the most common site of extracutaneous accumulation of mast cells in patients with systemic mastocytosis.35
The presence of certain clinical/laboratory features support bone marrow investigation when systemic mastocytosis is suspected in adult patients.37
Bone marrow evaluation should look out for multifocal dense infiltrates of mast cells (≥15 mast cells in aggregates) as a marker in systemic mastocytosis. Aberrant mast cells in bone marrow express CD25, with or without CD2, in addition to normal mast cell markers apparent in systemic mastocytosis. Specialty pathologist expertise may be required.5,34,38
High-sensitivity peripheral blood KIT D816V testing may aid in identifying patients who should have a bone marrow investigation when systemic mastocytosis is suspected in adult patients.5,37
Diagnosis of systemic mastocytosis per WHO diagnostic criteria requires presence of the major criterion and at least one minor criterion, or when ≥3 minor criteria are present
Screen suspected patients with high-sensitivity KIT D816V diagnostic assays.
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