A patient with chronic hepatitis C who obtained sustained response by retreatment of interferon after decrease of viral load and mutation in interferon sensitivity determining region

A 44-year-old man with chronic hepatitis C received three courses of interf eron (IFN) therapy. HCV genotype was Ib, viral load was 1,200 kcopies/ml an d interferon sensitivity determining region (ISDR) was the intermediate typ e before the Ist IFN therapy. The Ist and 2nd IFN therapies resulted in fai lure to yield a sustained response. Seven years after from the Ist therapy, viral load had decreased to 15 kcopies/ml and ISDR had changed to mutant t ype, The 3rd IFN therapy yielded sustained response. Thus, we should consid er retreatment with IFN when a decrease of the viral load and change of ISD R to mutant type are observed.