Association of Graves' Disease and Graves' Ophthalmopathy with the Polymorphisms in Promoter and Exon 1 of Cytotoxic T Lymphocyte Associated Antigen-4 Gene

Objective: To investigate the association of Graves' disease and Graves' ophthalmopathy with the C/T transition polymorphism at position -318 of promoter and the A/G transition polymorphism at position 49 of exon 1 within cytotoxic T lymphocyte associated antigen-4 (CTLA-4) gene.

Methods: Thirty-three patients with ophthalmopathy of Graves' disease, fifty-six Graves' patients without ophthalmopathy and sixty normal subjects as control were involved in the present case-control study. The polymorphisms were evaluated by polymerase chain reaction fragment length polymorphism (PCR-RFLP). Comparisons were made of gene frequencies and allele frequencies between the groups.

Results: The gene frequencies of CT and allele frequencies of T were much higher in Graves' patients with ophthalmopathy than that in the group without ophthalmopathy (P=0.020, P=0.019). The gene frequencies of GG and allele frequencies of G in patients with Graves' disease were significantly increased as compared with control group (P=0.008, P=0.007). The data suggest that smokers with Graves' disease seemed to be more predisposed to ophthalmopathy than non-smokers (P=0.018).

Conclusion: Our results suggest that an allele of T at position -318 of promoter is associated with genetic susceptibility to Graves' ophthalmopathy while an allele of G at position 49 of exon 1 is associated with genetic susceptibility to Graves' disease instead. Smoking is believed to be a major risk factor for ophthalmopathy.