++
Psoriatic arthritis manifests with inflammation at multiple sites of the musculoskeletal system, associated with symptoms and loss of function, and affects up to 1:3 people with psoriasis. Treatment is guided by disease phenotype which can present with combined features: peripheral arthritis defined by synovitis, increased vascularity and erosive and proliferative bone damage at large and small joints (PA), enthesitis, which is inflammation with increased vascularity and structural disruption of tendons and ligaments at site of insertions (E), dactylitis or inflammation crossing multiple anatomic layers of digits (D), and psoriatic axial spondyloarthritis characterized by inflammatory lesions affecting vertebrae and axial entheses and/or sacroiliac joints (axPsA). In treatment-naïve patients, we favor treating with a TNF inhibitor biologic over conventional DMARDs, though conventional DMARDs can be used as adjunctive therapy. If disease is refractory to initial therapy, IL-17 inhibitors and IL-12/23 inhibitors are considered, in this order, based on available evidence.1 Apremilast, leflunomide, and sulfasalazine can be used as adjunctive therapy in patients who cannot tolerate methotrexate, all, with the exception of apremilast, being used off-label for PsA. JAK inhibitors are reserved for patients with active PsA refractory to, or who cannot tolerate TNF inhibitors or other safer therapies. Musculoskeletal ultrasound is a useful tool to identify subclinical inflammation in arthritis, enthesitis, and dactylitis, and to guide procedural therapy for these phenotypes. For axial spondyloarthritis, MRI is the tool of choice to identify inflammatory disease activity and optimize therapy. Axial spondyloarthritis treatment options include TNF inhibitors or IL-17 inhibitors. See Table 51-1.
++