IFNL3 and obesity due to melanocortin 4 receptor deficiency: Several factors have been determined to be associated with the failure to respond to PEG-IFNα/RBV therapy and post-treatment relapse, including interleukin 28B single nucleotide polymorphisms (IL28B SNPs), gender, race, age, obesity [7–11], HCV genotypes, viral load, amino acid substitution in the CORE region, and a number of mutations within the NS5A region [12–14].