Yonsei Med J 49(1):159 - 162, 2008 DOI 10.3349/ymj.2008.49.1.159 Successful Etanercept Therapy for Refractory Sacroiliitis in a Patient with Ankylosing Spondylitis and Mixed Connective Tissue Disease Jee Young Lee,1 Hyun Kyu Chang,2 and Seong-Kyu Kim3 1Department of Diagnostic Radiology, College of Medicine, Dankook University, Cheonan; 2Chang Hyn Kyu Rheumatism Clinic, Cheonan; 3Department of Internal Medicine, Catholic University of Daegu School of Medicine, Daegu, Korea. The concurrence of ankylosing spondylitis (AS) in a patient with mixed connective tissue disease (MCTD) is rarely described in the literature. Significant and sustained efficacy with tumor necrosis factor (TNF)-α blockers has been demonstrated in AS patients. However, evidence to date has revealed associated side effects, including antinuclear antibody induction and development of a lupus-like syndrome. Several authors have reported lupus-like manifestations in MCTD patients treated with TNF-α blockers used to control peripheral polyarthritis. In our case report, we demonstrate a good response to etanercept therapy for refractory sacroiliitis in a patient with coexisting AS and MCTD, without development of a lupus-like syndrome. This demonstrates that etanercept therapy may be an appropriate therapeutic agent for sacroiliitis in MCTD patients, as it is in AS alone. Key Words: Ankylosing spondylitis, mixed connective tissue disease, etanercept INTRODUCTION Mixed connective tissue disease (MCTD) was first described as a distinct disease entity charac- terized by high titers of anti-U1-ribonecleic protein (RNP) antibodies.1 With certain sets of diagnostic criteria, clinical manifestations of MCTD are similar, or intermingled, with those of other connective tissue diseases, including systemic lupus erythematosus (SLE), polymyositis, and Received September 11, 2006 Accepted October 9, 2006 Reprint address: requests to Dr. Seong-Kyu Kim, Department of Internal Medicine, Catholic University of Daegu School of Medicine, 3056-6 Daemyung4-dong, Nam-gu, Daegu 705-718, Korea. Tel: 82-53-650-3038, Fax: 82-53-629-8248, E-mail: kimsk714 @cu.ac.kr systemic sclerosis.2 However, a concurrence of ankylosing spondylitis (AS) and MCTD has rarely been reported, in spite of their being clinically distinct entities.3,4 Most MCTD patients with arthritis respond well to treatment with nonsteroidal anti-inflammatory drugs (NSAIDs), hydroxychloroquine, and/or an oral, low-dose steroid. TNF-α blockers, including etanercept or infliximab, are also effective in controlling polyarthritis in MCTD patients,5,6 although side effects of lupus-like manifestations have been described. Treatment with TNF-α blockers in AS has also shown significant clinical efficacy.7,8 We present a patient with AS sacro- iliitis and MCTD who showed good response to etanercept without development of a lupus-like syndrome. CASE REPORT A 45-year-old female presented with Raynaud’s phenomenon, photosensitivity, edematous fingers and hands, and polyarthritis in April 2004. She also complained of a three-year history of low back pain with morning stiffness that improved with exercise and worsened with resting. Physical examination revealed symmetrical edematous fingers and hands bilaterally, with pain and limited motion of the right shoulder. Chest wall expansion was estimated at 3 cm, and lumbar spine motion was approximately 2 cm. Sacroiliac joint tenderness on palpation was noted. Immunological analyses revealed positive anti- nuclear antibody (ANA) with specked pattern Yonsei Med J Vol. 49, No. 1, 2008