In a series of recently published studies, Johns Hopkins researchers have shown that an intestinal disease affecting 400,000 people in the United States is actually a variety of related disorders that can be inherited and cause similar symptoms in close relatives. The findings will help physicians predict who will get the disease, called Crohn's disease, speed diagnosis, and help determine the best treatment for each individual.
"Although earlier studies had suggested that Crohn's disease might be several distinct disorders, this is the first large study of a group of families that confirms those suggestions," says Theodore M. Bayless, M.D., professor of medicine and gastroenterology.
The findings have prompted Bayless and his co-worker, Steven Brant, M.D., to encourage people with a family history of Crohn's disease to participate in a Hopkins study to identify the genes responsible for the disease.
Crohn's disease, which causes painful inflammation of the intestine and severe diarrhea, may appear in one of three forms: 1) a relatively mild form that remains localized in one area of the intestine; 2) intestinal scarring that eventually causes blockage of the intestine; and 3) a more dangerous form that sometimes perforates the intestinal wall.
In one study, published in the March issue of Lancet, the researchers found that the disease occurs earlier in life in people whose parents also have a history of Crohn's disease. This type of earlier onset of a more severe form of a hereditary disease in the child than in the parent is called genetic anticipation.
The study is the first to show genetic anticipation in a disorder caused by multiple genes, according to Bayless. The Hopkins team speculated that the disease, which is probably caused by mutations in several yet unidentified genes, may be made worse when there are numerous copies of these mutations, called a triplet repeat.