In this patient, it seems highly likely that PEG IFN treatment was responsible for the onset of interstitial pneumonitis since all other possible infectious or systemic causes were ruled out, there existed a temporal relationship between the peg-interferon treatment and the onset of interstitial pneumonitis, the absence of any previous pulmonary history, and the specificity of the results of the various investigations carried out in the context of the interstitial pneumonitis. The gene discussed is IFNA1; the disease is Interstitial pneumonitis.