A genetic association study in Japanese patients has narrowed the probable site of a gene responsible for inflammatory bowel disease (IBD) to a region within the intercellular adhesion molecule 1 (ICAM 1) gene on chromosome 19p13.

The study found a significant overall association between the K469E polymorphism of the ICAM 1 gene and IBD. The frequency of the allele was significantly higher in patients with IBD, Crohn’s disease (CD), and ulcerative colitis (UC) than controls. So was the rate of carriage (odds ratio 2.67; 95% confidence interval 1.2 to 6.15 for CD and 2.45; 1.27 to 4.86 for UC). Patients with CD affecting the small bowel and colon had more than five times the odds of carrying the allele and patients with entire UC nearly three times the odds, than controls.

The study screened peripheral blood from patients and controls for R241G and K469E polymorphisms of the ICAM 1 gene by restriction digestion of PCR products. The study sample included 207 patients with confirmed IBD, 79 with CD, and 128 with UC and 103 unrelated healthy volunteers.

A recent study showed significant linkage between IBD and chromosome 19p13. The current study was performed to confirm that relationship and the probable location of a candidate gene. ICAM 1 controls migration of inflammatory cells, and its gene has single base polymorphisms which help to identify genetic association in patients. The Japanese study population is considered to be genetically “pure” and especially suitable for linkage and association studies.