In patients undergoing surgery for PC, pre-treatment plasma YKL-40 correlated with plasma IL-6 (rho = 0.45, p<0.0001), serum CA 19.9 (rho = 0.40, p<0.0001) and age (rho = 0.40, p<0.0001). The gene discussed is CHI3L1; the disease is pachyonychia congenita.