This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skin, Subject name: Medicine
[{'content': "Skip lesions are seen in: (Repeat) \nSelect and explain. \nA. Crohn's disease, B. Ulcerative colitis, C. Ischemic bowel disease, D. Typhoid colitis", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans: A (Crohn's disease) Ref: Harrison's Principles of internal Medicine, 18ed.Explanation:Crohn's diseaseMC site-terminal ileum with rectal sparing, skip areas +It is transmural, hence more of fistula formationMore of systemic symptoms, pain, abdominal massToxic megacolon- PerforationIntraabdominal abscess, fallopian tube scarring - infertilityIntestinal obstruction, massive hemorrhage, malabsorption, severe perianal diseaseCobblestoning on endoscopeResponds to antibiotics, recurs after surgeryASCA-positiveTreatment - Antibiotics, corticosteroids, sulfasalazine, mercaptopurine. azathioprine, methotrexate, cyclosporine, tacrolimusAnti-TNF: Infliximab, adalimumab, certolizumab pegolAnti-integrin: NatalizumabRisk of Ca increases with duration & severity of the disease", 'role': 'assistant'}]