IBD Biomarker Discovery and Validation Platform

Eligibility Criteria: Inclusion Criteria: 1. General inclusion criteria for all participants: * Age 14 years or older. * Able to provide written informed consent; for minors, consent from a legal guardian and assent from the participant will be obtained according to local ethics requirements. * Willing to provide clinical information and/or biospecimens, which may include blood, stool, intestinal tissue, or other available biological samples. * Able to participate in study-related data and sample collection according to the study protocol. 2. Participants with inflammatory bowel disease: * Diagnosed with inflammatory bowel disease, including Crohn's disease, ulcerative colitis, or IBD-unclassified when applicable, according to accepted national or international diagnostic criteria. * May be newly diagnosed, previously diagnosed, under routine follow-up, or receiving routine clinical treatment. * Clinical data, treatment exposure information, laboratory results, endoscopic findings, histologic findings, imaging findings, biospecimens, and follow-up outcomes may be available or collected. 3. Unaffected first-degree relatives of participants with inflammatory bowel disease: * Biological first-degree relatives of participants with inflammatory bowel disease, including parents, siblings, or offspring. * No prior diagnosis of inflammatory bowel disease at enrollment. * Willing to provide clinical information and/or biospecimens for family-based genetic, environmental, immune, microbiome, and multi-omics analyses. 4. Unrelated healthy controls: * Individuals without a diagnosis of inflammatory bowel disease. * No first-degree biological relationship to enrolled participants with inflammatory bowel disease. * No known active gastrointestinal inflammatory disease at enrollment. 5. Non-IBD disease controls: * Individuals with gastrointestinal symptoms or other non-IBD conditions who undergo clinical evaluation but are not diagnosed with inflammatory bowel disease. * Clinical information and/or biospecimens may be collected as disease controls when appropriate. Exclusion Criteria: * Refusal or inability to provide informed consent or required assent when applicable. * Active severe infection or chronic infectious disease that may substantially affect biomarker interpretation, including active tuberculosis, active hepatitis B or C, HIV infection, or other clinically significant active infection. * Pregnancy or lactation at the time of enrollment. * Severe mental illness, cognitive impairment, or other condition that prevents cooperation with study procedures. * Known primary extraintestinal autoimmune disease or systemic inflammatory disease that is considered the main disease and may substantially confound biomarker interpretation. * Current or recent participation in another interventional clinical trial that may substantially affect the study biomarkers or outcome assessments, as judged by the investigator. * History of malignant tumor or other severe comorbidity that may substantially affect study participation or biomarker interpretation, as judged by the investigator. * Inadequate biospecimen quality, missing key clinical information, or inability to complete essential study assessments for the relevant analysis.