A subluxing arthropathy associated with the anti‐jo‐1 antibody in polymyositis/dermatomyositis

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Abstract
Of 180 patients with polymyositis/dermatomyositis (PM/DM) seen at the University of Pittsburgh and affiliated hospitals since 1975, 21 of 100 tested positive for the anti‐Jo‐1 antibody. Sixteen of the 21 patients were women and 18 were white. Fifteen had adult PM, 4 had myositis in overlap with scleroderma, and 2 had adult DM. Evidence of interstitial lung disease was found in 12 of 18 anti‐Jo‐1 positive patients (67%), but in only 15 of 79 anti‐Jo‐1 negative patients (19%) (P > 0.0002). The 21 anti‐Jo‐1 positive patients were divided into 3 separate groups based on the observed articular findings. Four patients had a deforming, predominantly nonerosive arthropathy with subluxations of the distal interphalangeal joints, especially the thumbs. Eight patients had a nondeforming arthropathy primarily affecting the small joints of the hands, wrists, shoulders, and knees. Those with deformities had a longer duration of arthritis compared with those with nondeforming arthropathy (mean 14.5 years versus 3.3 years). Nine anti‐Jo‐1 positive patients had no joint arthropathy. Three of 4 patients with deformities have required articular reconstructive surgery for subluxation, with 2 having associated subcutaneous calcinosis.