A subluxing arthropathy associated with the anti-Jo-1 antibody in polymyositis/dermatomyositis.

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 less than 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.