Uncommon Coexistence of Systemic Lupus Erythematosus and Psoriatic Arthritis: A Case-Based Review

Cases of systemic lupus erythematosus (SLE) following psoriatic arthritis (PsA) or vice versa are uncommon. Due to the complexity of autoimmune diseases and the rarity of such cases, comprehensive global data on the co-occurrence of these conditions are limited. Moreover, the pathophysiology concerning the coexistence of SLE and PsA has yet to be fully understood. Interestingly, the progression of both diseases appears to be significantly influenced by the key interleukin (IL) 17, particularly IL-17A. Here, we report 7 cases of SLE and PsA coexistence. In 5 of these cases, PsA occurred before the development of SLE, while in the remaining 2 cases, SLE was diagnosed before PsA. The PsA was characterized mainly by peripheral arthritis without any axial involvement, while the manifestations of SLE varied, with 3 developing systematic severe manifestations. Therapeutic challenges were posed in all cases, as treating one condition could worsen the other. Finally, we review the literature providing the current knowledge on the coexistence of these conditions. Overall, all reported cases emphasize the importance of personalized treatment and careful monitoring for patients with both SLE and PsA.