Presence of Other Autoimmune Diseases in Subjects with Autoimmune Thyroid Disease

Abstract

ders in patients with autoimmune thyroid diseases. The presence of coexisting autoimmune diseases was evaluated by a trained research nurse or specialist physician using a structured questionnaire seeking a personal history of common autoimmune disorders reported in Table 1. The authors found that patients with a primary diagnosis of autoimmune thyroid diseases are at increased risk of additional autoimmune disorders, such as rheumatoid arthritis, systemic lupus erythematosus, pernicious anemia, celiac disease, Addison’s disease, and vitiligo (Table 2). However, it is surprising that Sjogren’s syndrome, one of the most common systemic autoimmune disorders, was not included in these autoimmune disorders (Tables 1 and 2). In a populationbased study from Minnesota, the average annual age- and gender-adjusted incidence of physician-diagnosed Sjogren’s syndrome per 100,000 people was estimated to be 3.9 (95% confidence interval, 2.8-4.9). 2 Epidemiologic studies have shown prevalences of 0.6% to 1.6%, 3 which are higher than those of most of the autoimmune disorders presented in Table 1. In addition, it is well known from the literature that Sjogren’s syndrome is associated with other rheumatic and autoimmune conditions, especially autoimmune thyroid diseases. In a previous study from our department, a high prevalence of antinuclear antibodies was found in patients with autoimmune thyroid diseases compared with healthy controls (35% vs 9%, P .001). Sjogren’s syndrome was the most common coexisting autoimmune disorder, with a 9% prevalence in patients with autoimmune thyroid diseases with positive antinuclear antibodies. 4 These findings were confirmed by other studies showing that Sjogren’s syndrome was one of the most frequently detected autoimmune disorders among patients with autoimmune thyroid diseases. Soy et al 5 found that 10 (17.3%) of 65 patients with autoimmune thyroid diseases included in their study had coexisting Sjogren’s syndrome. Another study found that 13.7% of 218 examined patients with autoimmune thyroid diseases had at least 1 additional autoimmune disease; the 2 most frequent autoimmune diseases were systemic lupus erythematosus and Sjogren’s syndrome. 6 According to the above, clinicians caring for patients with autoimmune thyroid diseases should be alert to symptoms and signs of coexisting autoimmune diseases, including those of Sjogren’s syndrome.