Background: 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.
Materials and methods: 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.
Results: 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.
Conclusions: In summary, tryptase is a new diagnostic marker of myeloid neoplasms and a useful test in clinical haematology.