Bone marrow mast cells and mast cell tryptase in plasma cell disorders

Aim: Plasma cell disorders (PCD), a group of B-cell neoplasms, have undefined etiology. Mast cells (MC) have been found to promote the proliferation and differentiation of B cells in several B cell lymphoproliferative disorders; however, their role in PCD is unclear. The study therefore aims to evaluate bone marrow MC (BM-MC) in the context of PCD. Methods: Thirty patients with PCD and 20 control subjects were selected. The BM sample was collected and mononuclear cells were isolated to identify the MC percentage among mononuclear cells using flow cytometry. A 24-hour BM culture was also performed and tryptase levels in the culture supernatant were measured by an enzyme immunoassay. Results: In the patient group, the median of MC was 0.04% compared to 0.002% in the control group (p = 0.00001). Median BM-MC tryptase levels were also high in patients (10.1 ng/mL) against the control levels of 7.0 ng/mL (p = 0.011). While 50% of patients were found to have raised tryptase levels, only 10% of controls had tryptase levels beyond the cutoff levels of (p = 0.003). Conclusions: BM-MC number and tryptase levels are increased in PCD, suggesting their role in disease pathogenesis.