Infections and the risk of psoriatic arthritis among psoriasis patients: a systematic review.

Psoriasis and psoriatic arthritis (PsA) are related inflammatory diseases with some shared genetic and environmental risk factors. It has been suggested that environmental factors, including infections, can trigger the development of PsA among psoriasis patients. The aim of this review was to systematically examine available data evaluating the effect of infections on the risk of developing PsA. A systematic search of the Cochrane Library, PubMed, Scopus, and Web of Science was conducted on March 16 2017, in accordance with the PRISMA statement. The following search terms were used along with "psoriatic arthritis": "infections", "risk", "bacteria", and "virus". Abstracts were reviewed and publications meeting the following criteria included: (1) Observational studies on psoriasis and PsA patients, including case-control, cohort, or ecologic studies and (2) presenting original data on the association between infections and PsA. The protocol for this systematic review was registered on PROSPERO (ID: 79432). Twenty-seven original studies presenting data on infections among PsA patients were included. Eight studies showed a statistically significant association between infections and PsA. In addition, seven studies reported mixed result with some statistically significant associations and five studies did not find statistically significant associations. This included studies of bacterial as well as viral pathogens and those of infections in general. The remaining seven studies lacked data to determine statistical significance. Out of all included studies, the total number of included patients was 933 PsA patients and 1611 controls. While the studies summarized did not all provide evidence supporting an association between infections and PsA certain trends emerged. The available data are inconsistent and further studies are needed to verify or refute this purported association. In particular, laryngeal infections and infections involving streptococci should be studied more carefully.