Presence of Systemic Autoimmune Disorders in Patients with Autoimmune Thyroid Diseases

Objective: To evaluate the prevalence of antinuclear antibodies (ANA) in patients with autoimmune thyroid diseases (ATD) and the presence of systemic autoimmune disorders among ANA positive patients with ATD.

Methods: 168 consecutive patients with ATD with positive antithyroid antibodies and 75 healthy subjects were tested for the presence of ANA. ANA positive patients were further evaluated by complete history, physical examination, blood and urine tests, and immunological studies. Patients with subjective xerophthalmia and xerostomia were examined by objective tests.

Results: 58/168 (35%) patients with ATD were ANA positive compared with 7/75 (9%) healthy controls (p = 0.001). Of 58 ANA positive patients, 6 (10%) had anti-Ro antibodies, 1 had anti-Ro and anti-La antibodies, 7 (12%) had anti-dsDNA antibodies, and 7 (12%) had medium levels of IgG and/or IgM anticardiolipin antibodies (aCL). No healthy subjects had positive anti-dsDNA, antibodies against the extractable nuclear antigens, or aCL. 5/58 (9%) patients fulfilled the criteria for Sjögren's syndrome (SS). Two patients had features related to systemic lupus erythematosus. No healthy subjects had clinical or laboratory characteristics of systemic autoimmune disorders.

Conclusion: ANA are detected in 1/3 of patients with ATD. Anti-dsDNA, anti-Ro, and aCL can also be found in ANA positive patients with ATD. SS occurs in about 1/10 of ANA positive patients with ATD.