The proposed study is part of a PNRR 2022 project (call "Non-Communicable Chronic Diseases (NCDs) with high impact on healthcare and social assistance systems," currently awaiting funding response) and represents the continuation of an observational clinical study named TRANSMIC, approved by the pediatric ethics committee of the Tuscany region. TRANSMIC was an integral part of a European research project within the joint programming initiative (JPI), under the HDHL-INTIMIC theme: "A Healthy Diet for a Healthy Life," aimed at understanding the cause-effect relationships between diet, gut microbiome, and human health.

Understanding the role of diet in inflammatory bowel diseases (IBD) and exploring its role in autoimmune inflammatory conditions with joint manifestations, such as JIA, provides additional insights into the development, progression, and management of these conditions, opening new horizons for the use of dietary treatments in preventing these inflammatory conditions.

Inclusion Criteria:

For families with at least one child/adult affected by IBD/JIA:

• Father and mother with children aged between 0-18 years, in good health.
• At least one adult or one child affected by IBD, or a child affected by JIA, regardless of ongoing therapy and without distinction of disease severity or activity.

For healthy families:

- Father and mother with children aged between 0-18 years, in good health and not affected by chronic inflammatory bowel diseases or chronic autoimmune inflammatory diseases in general.

Exclusion Criteria:

For subjects affected by IBD:

• Monogenic disease
• Children with an ileostomy or who have undergone a colectomy

For subjects affected by JIA:

- No exclusion criteria

For healthy subjects:

- Any chronic inflammatory bowel disease, autoimmune disease, or ongoing infectious diseases.

Cases: Families consisting of father, mother, and children aged between 0 and 18 years, in good health, with at least one member (child or adult) affected by IBD (Crohn's disease or ulcerative colitis), and families with a child affected by JIA.

Controls: Healthy families consisting of father, mother, and children aged between 0 and 18 years, in good health, and not affected by chronic inflammatory bowel diseases or any chronic autoimmune inflammatory diseases.