In this proof-of-concept study, Maja Skov Kragsnaes and colleagues evaluated efficacy and safety of FMT in people with psoriatic arthritis (PsA). PsA is an inflammatory arthritis that causes a person’s joints to become stiff and painful. It is often found people with the skin condition psoriasis, and there is also a link between PsA and inflammatory bowel disease or gastrointestinal symptoms.