Objective: To evaluate the relevance of serum-free light chains (FLC) assessment in hepatitis C virus (HCV)-related lymphoproliferative disorders, including mixed cryoglobulinemia (MC) and B-cell non-Hodgkin's lymphoma (B-NHL).
Patients and methods: Fifty-nine HCV-infected patients were prospectively followed, including patients without MC (n=17), with asymptomatic MC (n=7), and with MC vasculitis (n=35, 9 of whom had B-NHL). Clinical and biologic data were recorded at the time of the initial evaluation and at the end of follow-up. Serum FLC quantitation was carried out using a serum FLC assay.
Results: The mean serum κ FLC level was higher in patients with asymptomatic MC (27.9±8.6 mg/L), MC vasculitis (36.7±46.2 mg/L) and B-NHL (51.3±78.3 mg/L) than without MC (21.7±17.6 mg/L) (P=0.047, 0.025 and 0.045, respectively). The mean serum FLC ratio was higher in patients with MC vasculitis (2.08±2.33) and B-NHL (3.14±3.49) than in patients without MC (1.03±0.26) (P=0.008). The rate of abnormal serum FLC ratio (>1.65) correlated with the severity of HCV-related B-cell disorder: 0/17 (0%) without MC, 0/7 (0%) asymptomatic MC, 6/26 (23%) MC vasculitis without B-NHL and 4/9 (44%) B-NHL (P=0.002). Serum κ FLC levels and the serum FLC ratio correlated with the cryoglobulin level (r=+0.32, P<0.0001, and r=+0.25, P=0.0016, respectively) and the severity of the B-cell disorder (r=+0.26, P=0.045, and r=+0.41, P=0.0012, respectively). Among patients with an abnormal serum FLC ratio at baseline, the FLC ratio correlated with the virological response to HCV treatment.
Conclusion: In HCV-infected patients, an abnormal serum FLC ratio appears to be a very interesting marker, as it is consistently associated with the presence of MC vasculitis and/or B-NHL. After anti-viral therapy, the serum FLC ratio could be used as a surrogate marker of the control of the HCV-related lymphoproliferation.