A false occult hepatitis B virus infection developed in a patient with psoriatic arthritis under infliximab and methotrexate therapy.

Despite lacking of international guidelines about the management of patients with occult hepatitis B virus infection (OBI) starting TNF-α blockers, there is some evidence from real life settings that these drugs are safe in OBI patients with rheumatic diseases. On the contrary, the management of the so-called false OBI patients appears still undefined. We describe a case of acute hepatitis B virus (HBV) infection occurred in an anti-HBs and anti- HBc positive patient affected by psoriatic arthritis, who had been treated for five years with infliximab. Baseline HBV-DNA analysis had not been performed. Although HBs Ag was still negative and the transaminases in the normal range, HBV-DNA serum analysis surprisingly showed high replication rate. Entecavir was added, and three months later HBV-DNA was no longer detectable. Even if HBs Ag is persistently negative, the assessment of HBV-DNA should be recommended at least at baseline in order to rule out hidden active necro-inflammatory liver disease.