Crohn's disease is a 55% chance the other will too. The incidence of Crohn's disease is increasing in Europe and in newly industrialised countries. For example, in Brazil, there has been an annual increase of 11% in the incidence of Crohn's disease since 1990. Inflammatory bowel diseases were described by Giovanni Battista Morgagni (1682–1771) and by Scottish physician T. Kennedy Dalziel in 1913. "Ileitis terminalis" was first described by Polish surgeon Antoni Leśniowski in 1904, although it was not conclusively distinguished from intestinal tuberculosis. In Poland, it is still called Leśniowski-Crohn's disease (). Burrill Bernard Crohn, an American gastroenterologist at New York
Paget's disease of bone percent of people with Paget's disease also have a family member with the disease. In cases where the disease is familial, it is inherited in an autosomal dominant fashion, although not all people that inherit the affected version of the genes will express the disease (incomplete penetrance). The incidence of Paget's disease varies considerably with geographic location. Paget's predominantly affects people of European descent, whereas people of African, Asian, or Indian descent are less commonly affected. Paget's disease is less common in Switzerland and Scandinavia than in the rest of Western Europe. Paget's disease is uncommon in the native populations