Jee Young Lee, et al. (titer of 1 : 1280, normal < 1 : 40), and positive anti-RNP antibody (titer of 965, normal < 150). Antibodies for double-stranded DNA, Sm, SS-A/ Ro, SS-B/La, centromere, Scl-70, and Jo-1 were negative. Anti-neutrophil cytoplasmic antibody, anti-cardiolipin antibody, cryoglobulin, VDRL, and rheumatoid factor were not detected. HLA- B27 antigen was positive. On radiographic examination of the pelvis, grade 2 bilateral sacroiliitis was diagnosed according to the modified New York classification. However, typical cervical and lumbar spine syndesmophytes were not identified. Magnetic resonance imaging (MRI) revealed active bilateral sacroiliitis (Fig. 1A). Echocardiography identified pulmonary arterial hypertension, with a pulmonary arterial pressure of less than 25 mmHg. Positive Raynaud’s phenomenon using Raynaud’s scan and infrared thermographic imaging was also confirmed. AS was diagnosed according to the modified New York criteria,9 and MCTD was diagnosed by the Alarcon-Segovia's criteria.10 Polyarthritis symptoms, except low back pain and Raynaud’s phenomenon, improved with combination therapy of hydroxychloroquine, NSAIDs, and low-dose corticosteroids, and right shoulder pain resolved following intraarticular steroid injection. Four months later, the patient was readmitted for buttock and sacroiliac joint pain. Clinically significant pain reduction was not achieved using computed tomography-guided intraarticular injec- tion of 40 mg of triamcinolone acetate. A 25-mg dose of soluble TNF-α receptor, etanercept, was started twice weekly for four weeks in combi- nation with NSAIDs and corticosteroids. The patient had pain reduction and no occurrence of A B Yonsei Med J Vol. 49, No. 1, 2008 lupus-like symptoms. MRI examination of the sacroiliac joint was assessed at 18 months. A significant decrease in inflammation was identified, without development of new lesions (Fig. 1B); this suggested the effectiveness of etanercept for sacroiliitis in patients with MCTD. Unfortunately, mild pulmonary arterial hypertension of approximately 37 mmHg developed. The patient’s treatment continued with NSAIDs, hydroxychloroquine, low-dose cortico- steroid, and a calcium channel blocker. She reported a tolerable level of low back pain around the sacroiliac joints. DISCUSSION MCTD patients share a number of clinical features, including Raynaud’s phenomenon, puffy hands, arthralgia, mild arthritis, myositis, and a high level of antibodies to U1-RNP. Several diagnostic criteria for MCTD have been described in patients with overlapping manifestations of SLE, RA, systemic sclerosis, and polymyositis.2 In addition, evidence of coexistence of spondyloar- thropathy and connective tissue diseases, especially Sjӧgren's syndrome or sicca syndrome, has pre- viously been described.11,12 Our case was a rare concurrence of AS and MCTD. Inflammatory manifestations in MCTD (including arthritis, serositis, fever, and skin rash) respond relatively well to NSAIDs or corticosteroids, whereas patients with major organ involvement tend to have persistent symptoms and often fail to have significant improvement of Raynaud’s phenomenon, interstitial lung disease, scleroderma- Fig. 1. (A) Magnetic resonance coronal fat suppressed T2-weighted image (WI) of both sacroiliac joints showing increased signal intensity within the joint spaces and subchondral marrow edema. Also present are subchondral erosions and localized fat deposition in the subchondral marrow spaces. (B) After 18 months, significant improve- ment of joint spaces with high signal intensity on fat-suppressed T2-WI with subchondral marrow edema identified at the same level.