Low Protein Z levels in patients with plasma cell neoplasms are inversely correlated with IL-6 levels

Patients with multiple myeloma (MM) have an increased thrombotic risk, but pathogenesis remains uncertain. Low levels of Protein Z (PZ), a vitamin K-dependent plasma protein, are associated with venous as well as arterial thrombosis. The purpose of this study was to analyze PZ levels in patients with plasma cell neoplasms. Patients and methods The study consisted of 64 plasma cells neoplasm patients and 42 healthy individuals. Clinical investigations included measurement of plasma PZ and IL-6 levels. Results PZ levels in patients with plasma cell neoplasms were significantly lower compared to healthy controls in the entire cohort (1392 ± 659 vs.2010 ± 603 ng/mL, P < 0.01), as well as in specific disease subgroups; symptomatic MM (1428 ± 652 ng/mL, p < 0.01), smoldering MM (1437 ± 883 ng/mL, p = 0.045) and monoclonal gammopathy of undetermined significance (MGUS) (1247 ± 593 ng/mL, p = 0.01). PZ was negatively correlated with IL-6 levels in MM patients (r = −0.7, P < 0.01). There was no significant difference in PZ levels between patients with or without thrombotic event. Conclusion Plasma cell neoplasm patients have low levels of PZ. This is presumably related to the increased IL-6 production by the bone marrow microenvironment, and could have a potential role in the increased thrombotic tendency in those patients.