Psoriasis and Inflammatory Bowel Disease

Background: Inflammatory bowel disease (IBD) and psoriasis (PS) are associated conditions. The reason for this association lies in the sharing of predisposition genes and common immunological mechanisms. Summary: This review will focus on the interplay between IBD and PS, with details on prevalence and phenotype of PS in IBD, genetics, pathogenetic pathways, and therapy. Key Messages: Microbiome seems relevant in both conditions: a reduction of beneficial bacteria has been observed. IBD and PS have in common some comorbidities like cardiovascular disease, similar risk of cancer and psychiatric problems. Many biological therapies such as anti-tumour necrosis factor (TNF) and anti-interleukin 23 are effective in both conditions, underlining the common immunological mechanisms. Paradoxical PS has been mainly observed after anti-TNF therapies, but preliminary reports show that it can also occur with other biologics. Genetic predisposition to this phenomenon has been reported.