Among 783 patients treated with anti-TNF (n = 472) or DMARDs only (n = 311), HBsAg−/HBcAb+ anti-TNF users had incidence of ALT elevation commensurate with uninfected counterparts (6.1 vs. 6.0/100 person-years), compared to 19.6/100 person-years in HBsAg+ patients (standardized rate ratio 3.3, 95% CI 1.3–8.2); none effected had severe or fatal hepatitis and ALT levels in all HBsAg−/HBcAb+ patients remained stable, mostly normalizing spontaneously, or after moderating treatment. The gene discussed is TNF; the disease is hepatitis A virus infection.