The Intestinal Microbiome in Juvenile Idiopathic Arthritis-Results of a Single-Center Pilot Study from Poland.

: Altered microbiome structures are perceived as one of the factors triggering the rise of autoimmune diseases, including juvenile idiopathic arthritis (JIA). Despite the extensive research conducted on rheumatoid arthritis (RA), data on microbiome compositions in pediatric populations are scarce and inconclusive. Moreover, no study has addressed this issue in Polish patients with rheumatic diseases. : The aim of our study was to compare diversity in the fecal microbiome and concentration of the intestinal permeability marker zonulin in patients with new-onset JIA and healthy subjects. : 15 treatment- naive patients with JIA and 15 age- and sex-matched controls qualified for the study. Analyses of fecal microbiome structure were performed using 16SrRNA gene sequencing, while concentration of serum zonulin was established using the ELISA method. : We found no statistically significant difference in alpha ( = 0.92) and beta diversity ( = 0.57)in the fecal microbiome between JIA patents and healthy children. Additionally, analyses of relative abundances of phyla, families, and genera identified no differences. Zonulin concentration did not vary ( = 0.88) between the study and control groups. : There is no statistically significant difference in fecal microbiome structure between new-onset JIA patients and healthy controls.