Humoral aspects of polymyositis/dermatomyositis

Abstract

Evidence of the involvement of systemic autoimmunity has been observed in polymyositis/dermatomyositis (PM/DM). Autoantibodies directed against various cellular constituents have been detected in most patients with PM/ DM, and about one-third of patients have autoantibodies (myositis-specific antibodies: MSAs) that are found specifically in myositis patients. These autoantibodies are closely associated with a characteristic clinical subgroup, and therefore help in establishing the correct diagnosis, classifying the myositis patients in a homogeneous subset, and facilitating the clinical and treatment follow-up. Autoantibodies to six of the aminoacyl tRNA synthetases are each associated with a similar syndrome marked by myositis, interstitial lung disease, arthritis, and other features constituting an "antisynthetase syndrome." Antibodies to other cytoplasmic antigens that are involved in protein synthesis or translation factors are seen in a small proportion of patients. Antisignal recognition particles are associated with severe, refractory myositis that differs significantly from antisynthetase syndrome. Antibodies to the nuclear antigen are specifically seen in patietnts with DM. Several autoantibodies, including anti-U1 RNP, anti-U2 RNP, anti-Ku, and anti-PM-Scl, have been associated with scleroderma-PM overlap. In recent years, these MSAs and their antigens have been characterized using molecular biology approaches. It is not known if the MSAs are involved in tissue injury or the pathogenesis of PM/DM. However, an understanding of the production mechanisms of these autoantibodies can provide insight into the etiology of this disorder.

A case of antisynthetase syndrome in a rheumatoid arthritis patient with anti-PL-12 antibody following treatment with etanercept

“…This report is very similar to our case in its clinical course. Although present case did not show myositis, patients with anti-Jo-1 antibody show myositis more frequently than those with anti-PL-12 antibody [8]. On the other hand, anti-PL-12 antibody is more associated with ILD than with myositis [14].…”

“…Antisynthetase syndrome is characterized by many clinical features, including mild to moderate grade fever; polyarthritis, usually without joint destruction; interstitial lung disease (ILD), especially NSIP; and characteristic skin eruptions called mechanic's hand, with or without inflammatory myositis in patients with anti-ARS antibodies [8]. Anti-ARS antibodies recognize ARSs in many cells, including myocytes; 6 major anti-ARS antibodies, of which the antigens are histidyl-(Jo-1) [9], alanyl-(PL-12) [10], threonyl-(PL-7) [11], isoleucyl-(OJ) [12], glycyl-(EJ) [12], and asparaginyl-tRNA synthetase (KS) [13], have been reported to date.…”