Vinod Chandran, MBBS, MD, DM, PhD
In most patients with psoriatic arthritis (PsA), the musculoskeletal manifestations occur after the onset of cutaneous manifestations. The mechanisms underlying the triggering of joint disease is still not well understood, one burning question is whether early and effective treatment of cutaneous psoriasis will reduce the incidence of PsA. In a retrospective non-randomised study, Gisondi et al compared the incidence rates of PsA in patients with chronic plaque psoriasis receiving either continuous treatment with a biologic disease modifying anti-rheumatic drugs (bDMARD- infliximab, etanercept, adalimumab, ustekinumab and secukinumab) for at least 5 years (n=234, 1584 person-year of follow-up) or at least three courses of narrow band ultraviolet B (nb-UVB) phototherapy (n=230, 1478 person-year of follow-up). bDMARDs treatment was associated with a lower risk of incident PsA (adjusted hazard ratio 0.27, 95% Confidence Interval 0.11–0.66). However, analysis after propensity score matching found no significant difference between treatment with bDMARDs and nb-UVB phototherapy and the risk of incident PsA. Prospective studies are required to answer this important question. Interestingly, nail psoriasis was associated with higher risk of PsA, confirming previous observations.
Due to lack of disease activity biomarkers clinical assessment of disease activity in PsA patients with concomitant fibromyalgia can be challenging. Ultrasound (US) may however be useful in providing objective assessment of disease activity . Polachek et al compared 42 patients with PsA and coexisting fibromyalgia syndrome (FMS) (satisfying CASPAR criteria and the 2016 fibromyalgia classification criteria) to 114 PsA patients without FMS (satisfying CASPAR criteria alone). All patients underwent detailed US evaluation including 52 joints, 40 tendons and 14 entheses, and a scores for synovitis, tenosynovitis and enthesitis were summed to obtain a final US disease activity score for each patient. Those with FMS had higher scores of composite clinical disease activity indices. However, the total US score and its subcategories were similar for those with and without FMS. The total US score significantly correlated with composite indices in PsA patients without FMS but not in PsA patients with FMS. Thus, US is a tool that can be employed to determine PsA disease activity in patients with concomitant FMS. However, the scanning protocol as described is time consuming. A shortened protocol as well as training of rheumatologists and radiologists for reliably assessing synovitis, tenosynovitis and enthesitis is required before US can be feasibly and reliably used in clinical practice.
IL-23 inhibitors were not found to be efficacious in the treatment of axial spondyloarthritis. It is not clear whether these inhibitors improve axial disease in PsA patients, and if indeed axial PsA is distinct from primary axial spondyloarthritis. In a post-hoc analyses of the DISCOVER 1 and DISCOVER 2 studies that included 312 patients with PsA with imaging-confirmed sacroiliitis randomly assigned to either placebo (n=118), guselkumab Q4 (n=103), or Q8 (n=91), Mease et al demonstrated that at week 24, guselkumab Q4 and Q8 groups vs placebo showed higher least-squares mean changes in BASDAI (−2.7 and −2.7 vs −1.3; P less than .0001) and ASDAS (−1.4 and −1.4 vs −0.7; P less than .0001) scores, which were maintained until week 52. Thus, Guselkumab may improve axial PsA . However, axial PsA has not yet been formally defined, and BASDAI and ASDAS are not specific for axial PsA. Once axial PsA is defined, prospective randomised clinical trials with associated MRI studies will be required to determine if IL-23 inhibitors improve symptoms of axial PsA.