Elevated tryptase levels selectively cluster in myeloid neoplasms: a novel diagnostic approach and screen marker in clinical haematology

Abstract

Recent data suggest that tryptase, a mast cell enzyme, is expressed in neoplastic cells in myeloid leukaemias. In several of these patients, increased serum tryptase levels are detectable. We have determined serum tryptase levels in 914 patients with haematological malignancies, including myeloproliferative disorders (n = 156), myelodysplastic syndromes (MDS, n = 241), acute myeloid leukaemia (AML, n = 317), systemic mastocytosis (SM, n = 81), non-Hodgkin's lymphoma (n = 59) and acute lymphoblastic leukaemia (n = 26). Moreover, tryptase was measured in 136 patients with non-neoplastic haematological disorders, 102 with non-haematological disorders and 164 healthy subjects. In healthy subjects, the median serum tryptase was 5.2 ng mL(-1). Elevated serum tryptase levels were found to cluster in myeloid neoplasm, whereas almost all patients with lymphoid neoplasms exhibited normal tryptase. Among myeloid neoplasms, elevated tryptase levels (> 15 ng mL(-1)) were recorded in > 90% of patients with SM, 38% with AML, 34% with CML and 25% with MDS. The highest tryptase levels, often > 1000 ng mL(-1), were found in advanced SM and core-binding-factor leukaemias. In most patients with non-neoplastic haematological disorders and non-haematological disorders analysed in our study, tryptase levels were normal, the exception being a few patients with end-stage kidney disease and helminth infections, in whom a slightly elevated tryptase was found. In summary, tryptase is a new diagnostic marker of myeloid neoplasms and a useful test in clinical haematology.