Anti-Tissue Transglutaminase Antibodies in Arthritic Patients: A Disease-specific Finding?

Tissue transglutaminase (tTG), widely distributed in human organs, is a multifunctional enzyme involved in the cross-linking of extracellular matrix proteins, fibrogenesis, and wound healing (1). Recently, tTG has been proposed as the autoantigen of anti-endomysial antibodies (EMAs) (2), a serologic marker of celiac disease (CD) (3). Use of anti-tTG antibodies has been advocated in the diagnostic work-up of CD (4), although positive results have been reported in patients with other intestinal disorders, such as inflammatory bowel disease (5)(6)(7). The aim of the present investigation was to evaluate the occurrence of anti-tTG-positive results in a cohort of arthritic patients, in whom the target organ is located at a distance from the intestine. Changes in anti-tTG antibodies were also investigated in patients with rheumatoid arthritis (RA) during treatment with methotrexate (MTX), a drug previously shown to decrease rheumatoid factor, soluble interleukin-2 receptor, and interleukin-6 (8). In this retrospective study, we enrolled 203 patients [121 males and 82 females; mean (SD) age, 51.4 (14.1) years; range, 17–76 years] attending our Rheumatological Unit in 1998–2000 and presenting without clinical signs and symptoms suggestive of CD. Of these patients, 183 belonged to three different groups: 74 had RA according to the American Rheumatism Association criteria (9); 67 had psoriatic arthritis (PsA) according to the European Spondyloarthropathy Study Group criteria (10); and 42 had ankylosing spondylitis (AS) according to modified New York criteria (11). The remaining 20, having knee, hand, or hip osteoarthritis (OA) according to the American College of Rheumatology criteria (12)(13)(14), were considered as disease controls. Sixty untreated CD patients [25 males and 35 females; mean (SD) age, 42.5 (11.2) years; range, 19–70 years], diagnosed according to the current criteria (15), were selected as disease controls. Fifty-four blood donors [26 males and 28 females; …