This long-term condition causes severe stomach pain and diarrhoea and it's on the increase, especially in young people. Yet doctors often fail to recognise it.
Miriam Kaltz was 22 when she visited her GP with abdominal pain that was making her reluctant to eat. The suggested diagnosis? That she had an eating disorder. "My doctor thought I was using this pain as an excuse not to eat," she says. "I hadn't even noticed I'd lost weight; I was more concerned about the symptoms and finding out what was causing them."
Kaltz, now 24 and a qualified vet, saw another GP and was referred to a consultant gastroenterologist. Following an MRI scan and a biopsy, she was finally diagnosed with Crohn's disease, a condition affecting the intestine that can result in severe diarrhoea, cramps, weight loss and extreme tiredness.
An estimated 250,000 people in the UK suffer from Crohn's and new figures suggest the disease is on the increase. According to the Health and Social Care Information Centre, the number of 16- to 29-year-olds receiving hospital treatment for the condition has risen 300% in the past 10 years, to almost 20,000. Why, then, is it still so hard for doctors to recognise the symptoms?
Janindra Warusavitarne, consultant colorectal surgeon at The London Clinic, says the early indications of Crohn's can be vague. "GPs see a lot of abdominal pain. They can't assume it's all Crohn's, especially as it could be something more acute," he says.
Kaltz is particularly frustrated by recent media reports that the rise in young people with Crohn's could be caused by junk food. "I didn't eat a single takeaway when I was growing up - my mum has Crohn's so it just wasn't something we did as a family."
The reports have also pointed at an increase in the use of antibiotics. "It's not as simple as saying this isn't true," says Warusavitarne. "Crohn's is an autoimmune condition, and there's obviously some trigger that causes the immune system to go into overdrive; we just don't know what that is. Junk food, antibiotics - it could be both, or neither. There's definitely a genetic link, but to say Crohn's is caused by x, y, or z - it's a much more complex disease than that."
Emma Kay-Flowers was diagnosed with Crohn's at the age of 17, after five months of symptoms. "I was so ill, I was just relieved to find out what was wrong with me and that there was medication that could ease my abdominal pains. I started on it right away, then saw a dietician."
Kay-Flowers, now 21, was advised to cut out all high-fibre foods and eat refined carbohydrates. "I tried this approach - I wanted to feel better. But it just seemed to make me feel bloated, and I had regular flare-ups. So I decided to swap all the white carbs for brown, and cut down on sugar. Gradually, my symptoms eased until, after two years, the flare-ups subsided completely."
In August 2013, Kay-Flowers went for a regular checkup. "My stomach felt completely different - like it had before my diagnosis. My consultant sent me for an MRI scan, which showed no signs of inflammation, just scar tissue where the Crohn's had been before. He took me off the medication and I was discharged. I've been well ever since."
This kind of recovery isn't common, but it does happen, says Warusavitarne. "The immune system fights and fights against itself and then it can just burn out and give up. But for most patients, a multidisciplinary approach to treatment is what works best."
This often means gastroenterologists and colorectal surgeons sitting down together with the patient. "We don't want to medicate, using immune suppressant drugs, and then, only when there are no further options, operate,' says Warusavitarne. "Surgery is not a failure of treatment - it's not to be taken lightly, but it can improve quality of life. And techniques in the past 25 years have improved enormously. With keyhole surgery, there is a quicker recovery time and less scarring."
Surgery for Crohn's works best when the inflammation of the intestinal tract is localised - enabling the diseased section to be removed. Other surgical approaches involve widening narrowed sections of intestine or, less commonly, creating an (often temporary) colostomy or ileostomy.
For Kaltz, having surgery is one of the best decisions she has ever made. Medication helped her symptoms but each time her dose was lowered, they would get worse again. "I was in my fourth year at university, and I was either missing classes because I was in the bathroom, or turning up and having to lie on the floor of the lecture theatre because I was in so much pain. Something had to give."
A portion of her small bowel was removed by keyhole surgery. "I was nervous, naturally, but I'd spoken to a friend of mine who has Crohn's and she'd had a similar procedure. She told me that afterwards I'd wonder what on earth I'd done, and she was right: I did feel pretty awful at first."
Kaltz made steady progress, though, and was out of hospital in eight days. She is careful about what she eats now, completely avoiding certain trigger foods (in her case, dairy produce, garlic, onions and wine). "I feel surgery has given me the chance to be healthy again," she says. "Everyone's Crohn's is different, but this is what worked for me. And I'm getting to do the job I've studied for years for."