Psoriatic arthritis (PsA) is a form of arthritis that affects individuals with the skin condition psoriasis (Ps). It is still unknown what leads to approximately 30% of psoriasis patients to eventually get PsA, a condition marked by significant joint pain among other symptoms. It has been hypothesized that changes to the homeostatic nature of the human microbiome may activate an inflammatory immune response in Ps patients, leading to the onset of PsA.
Scientists led by a group at NYU School of Medicine recently published a study in Arthritis and Rheumatology that showed patients with recently diagnosed PsA, who had yet to be treated, had lower gut bacterial diversity compared to Ps patients and healthy controls. They collected and sequenced 48 fecal samples from patients with PsA, Ps, and a healthy control group and identified the microbiota in each sample. Within the PsA samples, the abundance Akkermansia, Ruminococcus, and Pseudobutrivibrio microbes were decreased compared to the control subjects. The Ps samples showed a reduced abundance of Parabacteroides and Coprobacillus when compared to healthy and PsA samples. Analysis also showed that, correlating to the decrease of intestinal Akkermansia and Ruminococcus, PsA patients showed significantly reduced levels of MCFAs Hexanoate and Heptanoate, fatty acids derived from microbiota.
This study showed that PsA patients had lower levels of bacteria that are often described as beneficial and had gut profiles similar to patients with inflammatory bowel disease (IBD). The authors suggest a possible continuum in the loss of gut bacteria in the progression of the disease from psoriasis to psoriatic arthritis. While there are limitations to this study including the small number of subjects involved, it provides us with novel insight and investigation into the connection between gut bacteria and the onset of psoriatic arthritis. Further investigation is needed but this provides a target for the development of new interventions such as probiotics or prebiotics that would provide patients with the necessary bacteria that are missing in their gut.