This is a serious bowel disorder that produces patches of inflammation in the intestines, mostly in the second part of the small intestine (the ileum) or the large intestine (the colon). These patches have a characteristic appearance under the microscope. They may heal themselves in time, and some patients recover after just one or two attacks of Crohn’s disease. Others suffer recurring attacks throughout their lives. As they heal, the inflamed areas may develop scar tissue that narrows the intestine, making passage of food difficult. In terms of actual symptoms, Crohn’s disease produces diarrhoea, and cramps or more generalized pain in the abdomen, especially after eating. There is usually a general feeling of malaise and, sometimes, a slight fever. If left untreated, there is weight-loss and the health deteriorates because nutrients are not absorbed properly. Other symptoms, such as joint pains and mouth ulcers, often go with Crohn’s disease.

Despite intensive study, doctors still have no clear idea of what produces Crohn’s disease. The damaged areas of intestine, when studied under the microscope, contain a great many immune cells – it is these that produce the inflammation. The obvious explanation is that some infectious agent attracts them there – but there is no evidence that Crohn’s disease is infectious, and the fact that the disease mostly affects people in their twenties makes an infection unlikely. However, some researchers believe that they may now have found an infectious agent – a slow-growing bacterium related to the one that causes tuberculosis. Attempts to show that this bacterium really does produce Crohn’s disease are now in progress.