Abstract: diseaseRac1 is a regulator for cellular motility, proliferation andtransformation. A recent showed that mutations of RAC1gene are associated with higher risk of inflammatory boweldisease (IBD). These mutations increase the expression ofRac1 protein and intriguingly, loss of Rac1 expression resultsin protection from colitis [1,2].Thus we conducted a case-control study on 67 patientswith Crohn’s disease (CD) and 78 healthy individuals toidentify whether there is any association between CD andsingle nucleotide polymorphisms (SNPs) that increase theexpression of Rac1. All the patients were recruited fromGastroenterology Clinic of Imam Khomeini Hospital, a ter-tiary referral center affiliated to the Tehran University ofMedical Science. Both groups had Iranian originality. The ethics committee of Tehran University of Medical Sciencesapproved the study protocol and written informed consentwas obtained from each individual. Disease localization wasclassified as ileal, ileocolic, colonic and isolated involve-ment of upper gastrointestinal tract. Disease behavior wasdefined as: non-stricturing non-perforating or inflammatory;stricturing with persistent narrowing of intestinal lumen;and penetrating in which, intra-abdominal, enterocutaneousor enterovaginal fistulas were detected [3]. The distributionof alleles and genotypes of three RAC1 variants (rs1905198,rs836488, rs836488) were assessed by real time PCR. Allelefrequencies and genotypes were compared using the Chi2test.The mean age of patients was 36.7 ± 12.8 years withthe average age of disease onset at 29.8 ± 11.3 years.Twenty-two (37.9%) patients had ilecolic involvement, while19 (32.8%) had colic involvement. In 9 patients, illeal