[Influencing factors on occurrence and relapse in ulcerative colitis].

The concordance rate of monozygotic twins showed that the occurrence of ulcerative colitis required both internal and environmental conditions. Genetic studies revealed that IBD1 locus on chromosome 16 and IBD2 locus on chromosome 12 showed highly suspicious susceptibility for inflammatory bowel disease. The other possible internal factors include antineutrophil cytoplasmic antibodies and mucin abnormality. Many environmental factors have been reported to cause relapse. These are viral and bacterial infection, medicine such as antibiotics, non-steroidal anti-inflammatory drugs and aminosalicylates, colonic ischemia, post-examination state, psychological stress, winter season, travel and overwork.