This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Common site of regional enteritis is - \nSelect and explain. \nA. Colon, B. Rectum, C. Distal ileum and colon, D. Caecum', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Crohn disease (Terminal ileitis or regional enteritis) \n\nCrohn disease (CD) is an inflammatory bowel disease, characterized by -\n\n\nSharply delineated and typically transmural involvement of the bowel by an inflammatory process with mucosal damage.\nThe presence of non-caseating granulomas.\nFissuring with the formation of a fistula.\n\n\nAny portion of intention can be involved but most commonly small intestine is involved.\n\nSmall intestine → 40%\nSmall intestine + colon →\xa030%\nColon →\xa030%\n\nTerminal ileum involved most commonly and rectum is usually spared.\nCD is associated with HLA-DM1/DQw5 and NOD 2 genes and an abnormal T-cell response, particularly CD4 + T cells (Th1 cells)', 'role': 'assistant'}]