Inflammatory bowel disease in Japan: studies of epidemiology and etiopathogenesis.

The epidemiologic features of inflammatory bowel disease in Japan are somewhat different from the western features. Many immunologic abnormalities are observed, but without primary evidence for etiology. There are some differences regarding epidemiologic and immunologic aspects between ulcerative colitis and Crohn's disease. Bacteriovirological studies have not shown specific pathogens, but suggest that the enteric bacteria flora is significantly involved in the pathogenesis.