It is now established that genetic variations within IFNL3-IFNL4 gene region impact interferon-stimulated gene expression (ISGs) both in the liver and in PBMCs of CHC patients and are predictors of spontaneous and treatment-induced HCV clearance in both DAA- and IFN-based therapy [15–17]. The gene discussed is IFNA1; the disease is cryohydrocytosis.