Diagnostic Criteria for Systemic Mastocytosisa
| Major: Multifocal dense infiltrates of mast cells in bone marrow or other extracutaneous tissues with confirmation by immunodetection of tryptase or metachromasia |
| Minor: Abnormal mast cell morphology with a spindle shape and/or multilobed or eccentric nucleus |
| Aberrant mast cell surface phenotype with expression of CD25 and CD2 (IL-2 receptor) in addition to C117 (c-kit) |
| Detection of codon 816 mutation in peripheral blood cells, bone marrow cells, or lesional tissue |
| Total serum tryptase (mostly alpha) >20 ng/mL |
aDiagnosis requires either the major and one minor or three minor criteria.