Relationship between smoking and serum levels of eye muscle and orbital connective tissue antibodies in patients with Graves ophthalmopathy

Over the past three decades, several studies have quantified the risk of smoking in the development of ophthalmopathy in patients with Graves’ hyperthyroidism, with an overall odds ratio of approximately 3.0. Smokers also have a greater risk of more advanced ophthalmopathy than non-smokers. We studied 30 patients with Graves’ ophthalmopathy (GO) and 10 patients with upper eyelid signs as the only manifestation of ophthalmopathy, whose eye signs were assessed using the clinical activity score (CAS), NOSPECS classes and upper eyelid retraction (UER) score, half of whom were smokers and half of whom were non-smokers. Serum levels of eye muscle (CSQ, Fp2, G2s) and orbital connective tissue type XIII collagen (Coll XIII) antibodies are valuable markers of ophthalmopathy in patients with Graves’ disease. Still, their relationship to smoking has not been investigated. These antibodies were measured by enzyme-linked immunosorbent assay (ELISA) in all patients as a component of their clinical management. Mean serum antibody levels of all four antibodies were significantly greater in smokers than in non-smokers in patients with ophthalmopathy but not in those with upper eyelid signs only. As determined using one-way ANOVA and Spearman’s correlation test, there was a significant correlation between smoking severity, assessed as pack-years, with mean Coll XIII antibody level, but not with levels of the 3 eye muscle antibodies. These results suggest that in patients with Graves’ hyperthyroidism who smoke, the orbital inflammatory reactions are more advanced than in those with Graves’ hyperthyroidism who do not smoke. The mechanism of this enhanced Autoimmunity against orbital antigens in smokers is unclear and worthy of further study.