The present invention relates to biomarker genes for diagnosing and treating diseases. Provided herein are systems and methods of diagnosing a disease in a patient based on the patient s expression levels of biomarker genes. Examples of the TL1A associated disease include but are not limited to an inflammatory bowel disease (IBD) Crohn s disease (CD) ulcerative colitis (UC) and fibrosis. Also provided herein are systems and methods of identifying a patient likely to be responsive to an anti TL1A therapy prescribing and/or administrating an anti TL1A therapy to the patient based on the patient s expression levels of biomarker genes.
