A 62-year-old man presents to the GP with a history of diarrhoea. This has been occurring over the last six weeks, and he is now passing at least six stools a day. He has also lost around 7kg in weight. He had similar symptoms in his 20s, which worsened with smoking. On examination, he has multiple painful ulcers in his mouth and a soft abdomen with tenderness in the right iliac fossa. He is later seen in gastroenterology, where a colonoscopy is performed, showing areas of cobblestone mucosa separated by areas of normal mucosa.

What is the most likely diagnosis?

Options:
explanation: Irritable bowel syndrome causes diarrhoea/constipation, bloating and abdominal pain. Although it can be very distressing for some patients, it is not typically associated with any weight loss and does not cause any malabsorption or mouth ulcers. A colonoscopy would be normal in a patient with irritable bowel syndrome. Therefore, it is important to do the less invasive investigations first (e.g. blood tests, faecal calprotectin) to avoid performing any unnecessary procedures
name: Irritable bowel syndrome
label: e
answer: no
explanation: Gastroenteritis typically has a shorter time course, not usually more than a few weeks. As this is a six-week history, in the absence of any foreign travel that may suggest an atypical cause like _Giardia lamblia_, most causes of gastroenteritis should have resolved by now. This would also not explain the mouth ulcers, weight loss or colonoscopy findings
name: Gastroenteritis
label: c
answer: no
explanation: Ulcerative colitis is another type of inflammatory bowel disease; however, there are some key differences that distinguish it from Crohn's disease. Firstly, these patients are more likely to present with rectal bleeding as the area of mucosa affected almost always starts in the rectum. Smoking also characteristically relieves symptoms of ulcerative colitis, whereas they are worsened in this case. Finally, on colonoscopy, ulcerative colitis creates a continuous lesion without any cobblestoning, with typical features of ulcerative colitis including pseudopolyps and crypt abscesses. These differences make Crohn's disease the more likely diagnosis
name: Ulcerative colitis
label: b
answer: no
explanation: Colorectal cancer should always be considered in a patient over the age of 60 years old presenting with a new change in bowel habit according to NICE guidelines. However, this patient is also presenting with mouth ulcers, a previous episode of similar symptoms and pain on palpation of the right iliac fossa, which would not fit with the diagnosis of colorectal cancer. In addition, the colonoscopy findings are typical of Crohn's disease, and there was no indication of a mass that would suggest a diagnosis of colorectal cancer
name: Colorectal cancer
label: d
answer: no
explanation: Crohn's disease is a type of inflammatory bowel disease that can affect any area of the GI tract. It has a bimodal distribution, with a peak between 15-40 years old and 60-80 years old. Typical symptoms include abdominal pain, diarrhoea, weight loss, fever, malabsorption, mouth ulcers, perianal disease and systemic features (including dermatological, ophthalmic and rheumatological symptoms). Although it can affect any area of the GI tract, the ileocaecal junction is the most commonly affected area, which corresponds with the examination findings in this case. Although haematochezia may be seen in Crohn's disease, it is much more common in ulcerative colitis as the part of the GI tract affected in ulcerative colitis is usually more distal. Smoking exacerbates symptoms of Crohn's disease. Diagnosis involves blood tests (including ESR and CRP), faecal calprotectin and colonoscopy to confirm the diagnosis. Typical features on colonoscopy include skip lesions, cobblestone mucosa and non-caseating granulomas
name: Crohn's disease
label: a
answer: yes

Correct answer: a