Background: Infliximab, a chimeric monoclonal antibody against tumour necrosis factor (TNF) α is approved for psoriatic arthritis (PsA) treatment. Infliximab is available as an originator (Remicade®) and as biosimilar (CT-P13, Remsima®, Inflectra®; SB2, Flixabi®).
Case presentation: We present a 38-year-old Caucasian female diagnosed with PsA in 2009 with skin and joint symptoms. After multiple failed treatments including methotrexate, adalimumab, etanercept, certolizumab pegol and secukinumab, the patient was started on infliximab (Flixabi®). After 6 months, symptoms recurred and the patient was switched to infliximab (Remsima®) causing an allergic reaction. Based on the initial response to infliximab (Flixabi®) it was reintroduced. The patient did not develop any allergic reaction and responded excellently reaching controlled disease after 8 weeks with ongoing improvement of symptoms thereafter.
Conclusions: The reasons for the differential response to different infliximab products is unclear and may not necessarily be related to the antibody itself. While switching between bio-originator and bio-similar is widely practiced, we could not find another documented case of an allergic reaction to the infliximab bio-originator being exposed to an infliximab bio-similar later on.