{Reference Type}: Case Reports {Title}: TNFα inhibitor biosimilar associated with polychondritis. A case-based review. {Author}: Venetsanopoulou AI;Voulgari PV;Drosos AA; {Journal}: Rheumatol Int {Volume}: 43 {Issue}: 9 {Year}: 2023 09 15 {Factor}: 3.58 {DOI}: 10.1007/s00296-023-05364-9 {Abstract}: Relapsing polychondritis (RP) is a rare autoimmune disease characterized by inflammation of the cartilage structures of the body with typical features of auricular chondritis, nasal and ocular inflammation, audio-vestibular damage, as well as respiratory tract manifestations. It is associated with several autoimmune diseases and many other disorders. Tumor necrosis factor alpha (TNFα) inhibitors treat many chronic inflammatory disorders. They have proven effective and relatively safe in many clinical trials and observational studies. However, several autoimmune phenomena and paradoxical inflammation have been described with TNFα inhibitors, among them RP. This report presents a 43-year-old man with psoriatic arthritis treated with ABP-501 (Amgevita), an adalimumab (ADA) biosimilar and who developed RP, 8 months after the initiation of the treatment. This, is the first report of RP development during TNFα inhibitors biosimilar. We concluded that rheumatologists dealing with patients treated with TNFα inhibitors (originators or biosimilars), should be aware of several paradoxical reactions which may emerge and RP, is one of them.