Clin Rheumatol (2006) 25:240-245 DOI 10.1007/s10067-005-1165-y Edit Bir6 • Zoltfin Szekanecz • Lfiszl6 Czirjfik Katalin Dank6 • Emese Kiss • N6ra Anna Szab6 Gabriella Szfics • Margit Zeher • Edit Bodolay Gyula Szegedi • Gyula Bak6 Association of systemic and thyroid autoimmune diseases Received: 2 December 2003/Revised: 22 June 2005/Accepted: 22 June 2005/Published online: 25 October 2005 © Clinical Rheumatology 2005 Abstract Objective: There are few large cohort studies available on the association of systemic and thyroid autoimmune diseases. In this study, we wished to determine the association of Hashimoto's thyroiditis (HT) and Graves' disease (GD) with systemic autoim- mune diseases. Methods: One thousand five hundred and seventeen patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc), mixed connective tissue disease (MCTD), Sj6- gren's syndrome (SS) and polymyositis/dermatomyositis (PM/DM) were included in the study. The HT and GD were diagnosed based on thorough clinical evaluation, imaging and fine-needle aspiration cytology (FNAC). The frequency of HT and GD in these diseases was as- sessed. In addition, 426 patients with HT or GD were assessed and the incidence of SLE, RA, SSc, MCTD, SS and PM/DM among these patients was determined. Prevalence ratios indicating the prevalences of GD or HT among our autoimmune patients in comparison to prevalences of GD or HT in the general population were calculated. Results: Altogether 8.2% of systemic auto- immune patients had either HT or GD. MCTD and SS most frequently overlapped with autoimmune thyroid diseases (24 and 10%, respectively). HT was more common among MCTD, SS and RA patients (21, 7 and 6%, respectively) than GD (2.5, 3 and 1.6%, respec- tively). The prevalences of HT in SLE, RA, SSc, MCTD, SS and PM/DM were 90-, 160-, 220-, 556-, 176- and 69-fold higher than in the general population, respectively. The prevalences of GD in the same sys- temic diseases were 68-, 50-, 102-, 76-, 74- and 37-fold higher than in the general population, respectively. Among all thyroid patients, 30% had associated sys- temic disease. In particular, 51% of HT and only 16% of GD subjects had any of the systemic disorders. MCTD, SS, SLE, RA, SSc and PM/DM were all more common among HT patients (20, 17, 7, 4, 2 and 2%, respectively) than in GD individuals (2, 5, 5, 1, 2 and 1%, respec- tively). Conclusion: Systemic and thyroid autoimmune diseases often overlap with each other. HT and GD may be most common among MCTD, SSc and SS patients. On the other hand, these systemic diseases are often present in HT subjects. Therefore it is clinically impor- tant to screen patients with systemic autoimmune dis- eases for the co-existence of thyroid disorders. Keywords Autoimmune disease - Graves' disease • Hashimoto's thyroiditis • Overlap syndrome - Systemic autoimmune diseases Take home message: Autoimmune thyroid diseases, such as Ha- shimoto's thyroiditis and Graves' disease are often associated with systemic autoimmune diseases, most commonly with Sj6gren's syndrome and mixed connective tissue disease. E. Bir6 - Z. Szekanecz (N~) - K. Dank6 - E. Kiss N. A. Szab6 • G. Szfics • M. Zeher. E. Bodolay G. Szegedi - G. Bak6 3rd Department of Medicine, University of Debrecen Medical and Health Sciences Center, 22 Moricz street, 4004 Debrecen, Hungary E-mail: szekanecz@iiibel.dote.hu Tel.: +36-52-311087 Fax: + 36-52-414489 L. Czirjfik 2nd Department of Internal Medicine, University of P~cs, P6cs, Hungary Introduction There are well-known autoimmune overlap syndromes, where systemic and organ-specific diseases are associated with each other. Autoimmune thyroid diseases, such as Hashimoto's thyroiditis (HT) and Graves' disease (GD) preferentially form overlap syndromes with organspecific disorders including pernicious anaemia (PA), systemic or ocular myasthenia, Addison's disease (AD), immune thrombocytopenia (ITP), vitiligo, as well as with type 1 (insulin-dependent) diabetes mellitus (IDDM) [1-3]. There is relatively less information available regarding the overlap of HT or GD with systemic autoimmune disorders (reviewed in Refs. 1, 2, 4-6). There have been