Risk of inflammatory bowel disease in patients with psoriasis, psoriatic arthritis and ankylosing spondylitis initiating interleukin 17 inhibitors.

We read with great interest the article of Penso et al investigating whether IL17-inhibitors (IL17i) initiation is related to the greater risk of inflammatory bowel disease (IBD) in patients with psoriasis (PsO), psoriatic arthritis (PsA) and ankylosing spondylitis (AS) [1]. However, some points need to be discussed. Firstly, smoking is an important risk factor in IBD as it could affect the composition of intestinal microbiota and alter the immune system[2]. Although Crohn's disease (CD) and ulcerative colitis (UC) are the two main forms of IBD, sharing with some clinical features; they are different in smoking effect in which smoking exacerbates CD but it acts as a protective factor in UC[3].