Inclusion Criteria:  CASE:  - Newly diagnosed with JIA, IBD or T1DM  CONTROL:  - Brother/sister of child with pediatric onset inflammatory disease (same age category - same environment: diet, living environment)  Exclusion Criteria (case and control):  Child with antibiotic treatment in the 4 weeks preceding the stool sample Recent digestive infectious disease (bacterial, viral, parasitic) (end of episode < 7 days)  Exclusion Criteria (control): children with autoimmune or inflammatory disease