The association of other autoimmune diseases in patients with autoimmune thyroiditis: Review of the literature and report of a large series of patients.

We have evaluated prospectively the prevalence of other autoimmune disorders in outpatient clinic in 3069 consecutive patients with diagnosed chronic autoimmune thyroiditis (AT), with respect to two age- and sex-matched control groups: a) a control group of 1023 subjects, extracted from a random sample of the general population without thyroid disorders; b) 1023 patients with non-toxic multinodular goiter extracted from the same random sample of the general population, with similar iodine intake. The results of our study demonstrate a significant increase of the prevalence of autoimmune disorders in AT patients (with respect to both controls), for the following diseases: chronic autoimmune gastritis (CAG), vitiligo (Vit), rheumatoid arthritis, polymialgia rheumatica (Polym), celiac disease, diabetes, sjogren disease, multiple sclerosis, systemic lupus erythematosus, sarcoidosis, alopecia, psoriathic arthritis, systemic sclerosis, and HCV-related cryoglobulinemia. While the statistical analysis reached near the significance for Addison's disease and ulcerative colitis. Interestingly, the association of three autoimmune disorders was observed almost exclusively in AT patients, and the most frequent associations were AT+CAG+Vit and AT+CAG+Polym. We suggest that patients with AT who remain unwell, or who develop new not specific symptoms (despite adequate treatment) should be screened for other autoimmune disorders, avoiding the delay in the diagnosis of these disorders.