Background: Previous data have shown an association between DNA sequence variants in the IRF6 gene and an increased risk of non-syndromic cleft lip with or without cleft palate (CL/P) in some populations.
Objective: To investigate Thai CL/P patients and relative for a 820G-->A polymorphism.
Subjects: 192 CL/P Thai patients, 177 of their mothers, 73 of their fathers, and 278 controls.
Results: There were significant differences in the frequency distributions of both genotypes (p = 0.02) and alleles (p = 0.04) among probands as compared with the control group. The odds ratio calculated for the patients having the GG genotype compared with the other two genotypes (GA and AA) was 1.67 (95% confidence interval, 1.13 to 2.47). This pattern is consistent with a recessive effect of the G allele. No association between any of the parents' genotypes and CL/P was found. The IRF6 820G-->A was responsible for 16.7% of the genetic contribution to CL/P.
Conclusions: The findings confirm that IRF6 820G-->A is associated with CL/P.