Celiac disease is an immune-mediated disorder caused by a permanent gluten intolerance that primarily involves the small intestine. It is characterized by chronic inflammation of the small intestine's mucosa and submucosa. Genetic factors like HLA-DQ2 and DQ8 increase risk, and it is associated with other autoimmune disorders like type 1 diabetes, thyroid disease, and rheumatoid arthritis. The triggers are immunogenic peptides in gluten that are resistant to digestion and cause an immune response and damage to the intestinal lining.