Erosive arthropathy in amyopathic dermatomyositis.

Sirs, Articular symptoms are reported in 25-50% p atients with idiopathic infl a m m at o ry myopathies (IIM) (1,2). Arthropathy in IIM is typically symmetri c a l , n o n d e fo rm i n g and non-erosive (1-4). A subluxing arthropathy, which may be associated with eros i o n , has been described in IIM pat i e n t s with anti-synthetase antibodies (2, 4-9). We report a patient with amyopathic dermatomyositis who developed seve re ero s ive arthropathy involving both shoulders during the course of his disease. An erosive arthropathy affecting the proximal joints, in the absence of ove rl apping fe at u res of other connective tissue diseases (CTDs),has hitherto not been reported in dermatomyositis. A 45-year-old Chinese male presented in January 2001 with polyarthralgia, proximal myalgia and subacute onset of erythematosus skin rash over his face and hands. Examination revealed the typical heliotrope rash on his upper eyelids, and classic Gottron’s papules on the knuckles of the hands. There was periungual vasculitis and Raynaud’s phenomenon, but no proximal muscle weakness. Muscle enzymes were normal as we re the electro myographic fi n dings. The patient did not have any systemic ab n o rm a l i t i e s , s i c c a , dy s p h agia or skin t h i cke n i n g. Th e re was no hy p e rke rat o s i s , scaling or fissuring of the palms and fingers (mechanic’s hands). A biopsy of the lesional skin showed interface dermatitis without immunoglobulin deposits at the dermo-epid e rmal junction, wh i ch was compat i bl e with dermatomyositis. Screening for common malignancies in our locality was negat ive. A NA , a n t i d s D NA and rheumat o i d factor we re negat ive, as we re anti-ENA (nRNP, Sm, Ro, La, Scl-70) antibodies on both counteri m mu n o e l e c t ro p h e resis and We s t e rn bl o t t i n g. A n t i Jo-1 antibody wa s negative twice by immunoblotting. Chest X-ray showed minimal basal lung fibrosis; lung volumes and diffusion capacity were normal. There was no radiological evidence of erosive arthropathy of the wrists, hands and feet or periarticular calcification. There were also no overlapping features of other CTDs. The patient was treated with topical corticosteroid and hydroxychloroquine (300 mg/ day) and the skin rash gradually improved. In December 2001 he developed swelling of his right forearm and a fascial biopsy revealed eosinophilic fasciitis which responded well to prednisolone and azathioprine. The patient remained well until March 2002 when he developed bilateral shoulder pain. E x a m i n ation revealed bilat e ral shoulder arthritis with reduction in joint movement. The response to NSAIDs and intra-articular steroid was poor. Plain radiographs of the shoulder joints showed extensive symmetrical bony erosions of the glenoids and h u m e ral heads. Subcutaneous calcinosis was also noted at the axillary regions. MRI of the shoulder joints confirmed severe erosive arthritis involving both gleno-humeral joints. The deltoid muscles and bone marrow of the humeral heads showed high signal intensity due to muscle and bone edema on T2-weighted ima ges with fat saturation. Mild atrophy of the deltoid muscles was noted. Gadolinium enhanced images showed intense enhancement of the thickened synovium (Fig. 1). There was no evidence of avascular bone necrosis. As he is a chronic hepatitis B carrier with possible active hepatitis, methotrexate was not considered. Intramuscular gold therapy was given with partial response. The arthropathy of IIM usually affects the distal peripheral joints. Hand arthritis with erosions, periosteal calcification, and interphalangeal thumb joint instability has been reported in patients with polymyositis and “overlap” features such as Raynaud’s phenomenon, positive ANA, and LE cell phenomenon (8). Another study described 9 IIM patients with interstitial lung disease and infl a m m at o ry art h ro p at hy (3). Eight had mild non-erosive arthritis while one had e rosions and peri a rticular calcifi c at i o n s . The status of the anti-synthetase antibodies was unknown in these early studies. The presence of anti-synthetase antibodies in IIM patients marks a distinct clinical subset. In a large series those with the antibodies were found to have significantly more frequent arthritis, fever, interstitial lung disease and “ m e ch a n i c ’s hands” than those without (10); 33-57% had clinical arthritis (10). A subluxing or deforming non-erosive arthropathy has been reported in patients with the anti-Jo-1 antibody, with or without evidence of myositis (5, 9). Occasionally, the arthropathy was erosive and associated with peri a rticular calcifi c ation due to apatite deposition (4,6,7). Involvement of the distal joints such as the wrists and hands was usual. Our patient was unique in that he developed severe bilateral erosive arthropathy of both s h o u l d e rs without invo l vement of other peripheral joints. He did not fulfill the ACR criteria for RA. There were no overlapping fe at u res of other rheumatic diseases that might have contributed to the articular erosion. Although his anti-Jo-1 was negative, it remains possible that other anti-synthetase antibodies such as anti-PL-7, a n t i P L 1 2 might have been present. Erosive arthropathy of the proximal joints should be recogn i zed as a possible evolving fe at u re in patients with dermatomyositis.