Myositis autoantibodies in Korean patients with inflammatory myositis: Anti-140-kDa polypeptide antibody is primarily associated with rapidly progressive interstitial lung disease independent of clinically amyopathic dermatomyositis

<p>Abstract</p> <p>Background</p> <p>To investigate the association between myositis autoantibodies and clinical subsets of inflammatory myositis in Korean patients.</p> <p>Methods</p> <p>Immunoprecipitation was performed using the sera of classic polymyositis (PM) (n = 11) and dermatomyositis (DM) (n = 38) patients who met the Bohan and Peter criteria for definite inflammatory myositis. A panel of defined myositis autoantibodies was surveyed to investigate the association between each autoantibody and clinical subsets of inflammatory myositis.</p> <p>Results</p> <p>Either MSAs, anti-p140, or anti-p155/140 antibodies were found in 63.3% (31/49) of the study subjects. Anti-140-kDa-polypeptide (anti-p140) (18.4%, 9/49) and anti-155/140-kDa polypeptide (anti-p155/140) (16.3%, 8/49) antibodies were the most common, followed by anti-Mi2 (14.3%, 7/49), anti-ARS (12.2%, 6/49) and anti-SRP (2.0%, 1/49) antibodies. All MSAs and anti-p140 and anti-p155/140 antibodies were mutually exclusive. Anti-p140 (23.7%, 9/38), anti-p155/140 (21.1%, 8/38), and anti-Mi2 (18.4%, 3/38) antibodies were found exclusively in DM patients. Anti-p140 antibody was associated with rapidly progressive interstitial lung disease (ILD) (p = 0.001), with a sensitivity of 100.0% (4/4) and a specificity of 85.3% (29/34) in DM patients. Anti-p155/140 antibody was associated with cancer-associated DM (p = 0.009), with a sensitivity of 55.6% (5/9) and a specificity of 89.7% (26/29). Cancer-associated survival was significantly worse when anti-p155/140 antibody was present (19.2 ± 7.6 vs. 65.0 ± 3.5 months, p = 0.032). Finally, anti-ARS antibodies were associated with stable or slowly progressive ILD in PM and DM patients (p = 0.005).</p> <p>Conclusions</p> <p>Anti-p140 and anti-p155/140 antibodies were commonly found autoantibodies in Korean patients with inflammatory myositis. Despite the lack of clinically amyopathic DM patients in the study subjects, a strong association was observed between anti-p140 antibody and rapidly progressive ILD. Anti-p155/140 antibody was associated with cancer-associated myositis and poor survival.</p

Low copy numbers of complement C4 and C4A deficiency are risk factors for myositis, its subgroups and autoantibodies

Background Idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases characterised by myositis-related autoantibodies plus infiltration of leucocytes into muscles and/or the skin, leading to the destruction of blood vessels and muscle fibres, chronic weakness and fatigue. While complement-mediated destruction of capillary endothelia is implicated in paediatric and adult dermatomyositis, the complex diversity of complement C4 in IIM pathology was unknown. Methods We elucidated the gene copy number (GCN) variations of total C4, C4A and C4B, long and short genes in 1644 Caucasian patients with IIM, plus 3526 matched healthy controls using real-time PCR or Southern blot analyses. Plasma complement levels were determined by single radial immunodiffusion. Results The large study populations helped establish the distribution patterns of various C4 GCN groups. Low GCNs of C4T (C4T=2+3) and C4A deficiency (C4A=0+1) were strongly correlated with increased risk of IIM with OR equalled to 2.58 (2.28-2.91), p=5.0×10 -53 for C4T, and 2.82 (2.48-3.21), p=7.0×10 -57 for C4A deficiency. Contingency and regression analyses showed that among patients with C4A deficiency, the presence of HLA-DR3 became insignificant as a risk factor in IIM except for inclusion body myositis (IBM), by which 98.2% had HLA-DR3 with an OR of 11.02 (1.44-84.4). Intragroup analyses of patients with IIM for C4 protein levels and IIM-related autoantibodies showed that those with anti-Jo-1 or with anti-PM/Scl had significantly lower C4 plasma concentrations than those without these autoantibodies. Conclusions C4A deficiency is relevant in dermatomyositis, HLA-DRB1∗03 is important in IBM and both C4A deficiency and HLA-DRB1∗03 contribute interactively to risk of polymyositis

Prevalence in myositis of antibodies recognizing anti-U3 RNA probably in a novel complex with 22/25 kD protein and not fibrillarin

New antibodies against a U3 snRNP, which were named anti-Myo 22/25 antibodies, were detected in four (8%) of 53 serum samples from patients with polymyositis/dermatomyositis (PM/DM) by RNA immunoprecipitation. In the protein immunoprecipitation analysis, all four serum samples precipitated 22 kDa and 25 kDa proteins, which were not precipitated by normal serum or serum positive for antifibrillarin antibodies. Three of the four PM/DM patients had other identified autoantibodies including anti-PL-12 antibodies, antihistone antibodies (AHA), anti-SS-A antibodies and anti-SS-B antibodies defined by double immunodiffusion, ELISA or RNA immunoprecipitation, although there were no significant correlations between anti-Myo 22/25 antibodies and clinical or laboratory findings. There may be a subgroup of PM/DM patients whose sera are positive for anti-Myo 22/25 antibodies