Clinical, serologic, and immunogenetic features in Polish patients with idiopathic inflammatory myopathies

Abstract

Objective: To determine the clinical, serologic, and immunogenetic correlations in patients with idiopathic inflammatory myopathies (IIM), and to evaluate the useful grouping of some diseases for practical clinical purposes.

Methods: Patients with IIM were categorized according to clinical presentation as compared with autoantibody specificity. Serum samples from 84 patients were screened for myositis-specific autoantibodies (MSAs) by indirect immunofluorescence and double immunodiffusion. All sera were also studied by protein A-assisted immunoprecipitation. Genomic DNA was isolated from peripheral blood mononuclear cells, and HLA-DQA1 and DRB1 alleles were determined. The patients were seen and followed up for many years in the same center.

Results: MSAs were present in 19% of patients. The most common MSAs were antisynthetases in 13% of patients (Jo-1 10.7%, PL-12 1.2%, and EJ 1.2%), associated with the antisynthetase syndrome. Anti-SRP was found in 1.2% of patients, associated with polymyositis, and anti-Mi-2 in 4.9%, found exclusively in patients with dermatomyositis. The most frequent MSA was PM-Scl in 23.8% of patients, associated with scleromyositis, and Ku was present in 9.6% of patients with overlap syndromes. The alleles that were found at a significantly increased frequency were HLA-DRB1*0301 (59.4%) and DQA1*0501 (71.6%), which are in linkage disequilibrium. DQA1*0501 was present in 85.7% of patients with antisynthetases, and in 100% of patients with PM-Scl and Ku.

Conclusion: The HLA-DRB1*0301; DQA1*0501 haplotype was found to be significantly increased in this population overall and in those myositis patients with antisynthetase, anti-PM-Scl, and anti-Ku antibodies. The results of this study confirm that IIM are heterogeneous syndromes, but can be divided into more useful groups on the basis of clinical, serologic, and immunogenetic features.