Psoriatic arthritis (PsA) is a chronic inflammatory condition that typically follows psoriasis (PsO), with skin involvement often preceding joint issues, though joint pain and bone destruction can also come first. PsA commonly presents as symmetrical polyarthritis, distinct from rheumatoid arthritis (RA) by its involvement of distal interphalangeal joints and the absence of subcutaneous nodules. Dactylitis, involving enthesitis and synovitis in the digits, is another key feature. PsA shares similarities with RA but also includes unique features like enthesitis and increased synovial vascularity.

IL-17 plays a critical role in PsA by promoting inflammation through its effects on keratinocytes and synovial cells. It bridges the innate and adaptive immune systems, contributing to chronic inflammation. Targeted therapies blocking the IL-17 pathway, such as secukinumab, the first IL-17A monoclonal antibody approved for PsA in 2016, have shown promise. Other therapies targeting the IL-17 receptor, like brodalumab and ixekizumab, are under study. Additionally, IL-23/IL-17 signaling plays a key role in PsA, and biologics like ustekinumab, targeting the p40 subunit of IL-12/IL-23, have been successful. Ongoing clinical trials on IL-17-targeted therapies and bispecific TNF/IL-17A inhibitors offer new treatment options.

Reference: Wang EA, Suzuki E, Maverakis E, Adamopoulos IE. Targeting IL-17 in psoriatic arthritis. Eur J Rheumatol. 2017 Dec;4(4):272-277. doi: 10.5152/eurjrheum.2017.17037. Epub 2017 Nov 10. PMID: 29308283; PMCID: PMC5741341.