Biologic treatments for psoriasis have different anatomical specificities in residual PASI

Summary Background and objectives Improved understanding of the immunopathogenesis of psoriasis has led to the development of effective targeted therapies, but patients who respond to treatment without total skin clearance have residual disease. The aim of this study was to demonstrate the existence of specific residual disease (or residual PASI) anatomical localizations related to different biologic agents. Methods and patients This retrospective, observational, multi‐center study analyzed clinical data of patients affected by psoriasis who had received biologic treatments for at least 6 months. The data analysis focused on patients with residual PASI. Results A total of 228 of 1,000 patients showed residual disease despite achieving PASI 90 at weeks 24–28 of biologic treatment. The anatomical sites most frequently involved in residual disease were the lower limbs (44.3%). We observed differences among the biologic agents in terms of frequency and localization of residual disease. The localization of residual skin lesions to lower limbs was associated with treatment switching/interruption. The drugs with the highest and lowest proportion of patients with residual disease in the lower limbs were, respectively, secukinumab and risankizumab. Conclusions Treatment with anti‐IL‐17 and anti‐IL‐23 drugs is characterized by the persistence of residual skin lesions with differences in terms of frequency and anatomical localizations.