Psoriatic Arthritis
Many patients with psoriasis and PsA have associated subclinical gut inflammation. Decreased bacterial diversity due to lower abundances of several taxa were demonstrated. The authors found Coprococcus to be inversely associated with psoriasis with or without arthritis (PsA), whereas a decline in relative abundance of Ruminococcus and Akkermansia were unique to PsA. This is of particular interest as Ruminococcus are also reduced in abundance in patients with IBD. Moreover, the decreased abundance of Akkermansia in PsA contrasts to that of juvenile SpA, indicating distinct microbes may also drive the cause of these diseases.
Another gut commensal found in healthy populations, Alistipes, was lower in abundance in both PsA and Crohn's disease. Many of these microorganisms play a role in degrading mucus and producing SCFAs that influence gut homeostasis. A hallmark of dysbiosis in these individuals may be a loss of commensals, disrupting immune homeostasis.