Autoimmune thyroid disease is associated with a diagnosis of secondary Sjogren's syndrome in familial systemic lupus

Background: Autoimmune thyroid disease is common in systemic lupus erythematosus (SLE). About 20% of patients with SLE have secondary Sjogren's syndrome. Methods: Families with more than one patient with SLE were identified. All patients met the revised classification criteria, although SLE-unaffected relatives were confirmed not to satisfy these criteria. Diagnosis of autoimmune thyroid disease and Sjogren's syndrome was made on the basis of a review of medical records, interview and questionnaire administered to patients with SLE, and by a questionnaire administered to SLE-unaffected subjects. Results: Of a total of 1138 patients with SLE, 169 had a diagnosis of Sjogren's syndrome. Of these 50 (29.6%) patients also had autoimmune thyroid disease. Of the 939 patients with SLE with no diagnosis of Sjogren's syndrome, 119 (12.7%) had autoimmune thyroid disease (chi(2)=20.1, p=0.000009). There was no association of a diagnosis of hypertension with secondary Sjogren's syndrome (42% vss 47%). Among 2291 SLE-unaffected relatives, 44 had diagnosed primary Sjogren's syndrome and 16 (36.3%) of these also had autoimmune thyroid disease. 265 of 2247 (11.8%) subjects had autoimmune thyroid disease but no Sjogren's syndrome (chi(2)=24.2, p < 0.001). Conclusions: Autoimmune thyroid disease is found in excess among patients with SLE with a diagnosis of secondary Sjogren's syndrome, as well as among their SLE-unaffected relatives with a diagnosis of primary Sjogren's syndrome.