Through global cooperation, all the major laboratories active in research on Crohn’s disease succeeded in obtaining a very precise genetic map of this inflammatory disease of the digestive system. The genetic heritage of some 75,000 patients was thoroughly examined. With 163 genetic variations identified, Crohn’s is currently the best genotyped disease. A great hope for sufferers. But the research published in Nature magazine (1), which a team from the University of Liège’s Giga Research collaborated on, also revealed the great complexity of a pathology that is undoubtedly the result of war waged by our body in the past against terrible microbes such as tuberculosis or the plague.

Petrus opened the door; a ray of sunshine slipped into the house and lit up the only room in the modest dwelling. Six corpses lay on the dirt floor: his father, his mother, his sister and his three brothers. It was the same macabre scene in the neighbouring houses: lifeless bodies everywhere, covered in buboes.  That week, the plague had wiped out the whole village. The epidemic had arrived in the town two weeks earlier with a distant cousin who had returned from the war against the English. The carnage had begun several days later. Only Petrus had survived. “Why me?” he wondered amid all this desolation. He beseeched the Lord to provide him with an answer.

Pierre opens the door of Dr. Deliège’s surgery. He has come to find out the results from a colonoscopy that was carried out the previous week at Liège CHU. He’s anxious. He’s been suffering from abdominal pain and chronic diarrhoea for several months now. He finally decided to see a doctor when he realised he’d lost five kilos. “You’re suffering from a chronic inflammation of the intestine”, the doctor told him, “Crohn’s disease. Don’t worry, it won’t kill you. But I have to be honest with you, you can’t get rid of it either. There is treatment available to relieve the symptoms, but when the disease evolves too quickly, we sometimes have to surgically remove part of the intestine”. Pierre is bewildered: “I don’t understand, I don’t drink alcohol, I eat healthily...” “We still don’t really know what causes this disease”, the doctor replies. "There is clearly a strong genetic component. By comparing the genetic heritage of people with and without the disease, researchers have identified 163 precise places on the genome that could be involved in the disease. It's possible that the genes that cause this chronic inflammation of the digestive system today, allowed our ancestors to escape the plague epidemics in the Middle Ages. A French researcher supports this theory. And a recent study published in Nature is grist to the mill.”

(1) Host-microbe interactions have shaped the genetic architecture of inflammatory bowel disease. Published in Nature online 01 November 2012.