To evaluate the relevance of serum-free light chain (FLC) assessment in hepatitis C virus (HCV)-related lymphoproliferative disorders, including mixed cryoglobulinemia (MC) and B cell non-Hodgkin lymphoma (B-NHL).
A total of 59 patients infected with HCV 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 biological 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.
The mean (SD) serum kappa FLC level was higher in patients with asymptomatic MC (27.9 (8.6) mg/litre), MC vasculitis (36.7 (46.2) mg/litre) and B-NHL (51.3 (78.3) mg/litre) than without MC (21.7 (17.6) mg/litre) (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 kappa FLC levels and the serum FLC ratio correlated with the cryoglobulin level (r = 0.32, p<0.001 and r = 0.25, p = 0.002, respectively) and the severity of the B cell disorder (r = 0.26, p = 0.045 and r = 0.41, p = 0.001, respectively). Among patients with an abnormal serum FLC ratio at baseline, the FLC ratio correlated with the virological response to HCV treatment.
In patients infected with HCV, 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 antiviral therapy, the serum FLC ratio could be used as a surrogate marker of the control of the HCV-related lymphoproliferation.