Background Autoimmune myositis (AIM) is a syndrome characterized by involvement of the cellular and humoral immune systems in skeletal muscle pathology, response to immunotherapies, and the presence of autoantibodies in the serum of many patients1. AIM is commonly classified using the orginal classification proposed by Bohan and Peter2, as this approach has become subject to increasing debate. The analysis of the overlap clinical manifestations and the discovery of different antibodies led to serologic approaches complementary to the Bohan and Peter classification, because striking associations of antibodies and overlap clinical features3.
Objectives The objective of the study was to compare the original classification proposed by Bohan and Peter, modified classification and novel clinicoserologic classification, proposed by Y. Troyanov.
Methods We conducted a study of 95 adult patients with myositis seen at the Clinic of Rheumatology, Univesity hospital “St. Ivan Rilski”. First all patients were classified to the original Bohan and Peter classification. Second, we analysed clinical features and used the modified classification focus on overlap manifestations. Subsequently we tested the antibodies by Immunoblot test and enzyme linked immunosorbent assay and classified the patients to the Troyanov classification. The frequency comparison among groups were analysed by Chi-square method (Fisher's exact test).
Results According to the original classification polymyositis (PM) was the most frequent entity – 32% of the patients at diagnosis. However, using the modified classification, PM was a rare entity, occurring in only 13.75%, as it frequency fell to 11.25% with Troyanov classification (p<0.05, in comparison among clinicoserologic classification and original or modified classification). Using the original classification dermatomyositis (DM) was diagnosed in 25% of the cohort. According to the modified classification, the overall frequency of DM was 11.25%, and to tne clinioserologic classification, occurring in 7.5% of the patients (p<0.05, in comparison among novel classification and original or modified classification). Overlap myositis was present in only 30% of cases according to the Bohan and Peter original classification at diagnosis. When the modified classification and Troaynov classification were used, overlap myositis was the most frequent entity, respectively accounting for 63.75% and 70% of patients with myositis (p<0.05, in comparison among novel classification and original or modified classification). We determined the sensitivity (Se) of the novel clinocoserologic classification for diagnosis of overlap myositis in patients with myositis – Se=84%.
Conclusions The original Bohan and Peter classification leads to misclassification of patients with myositis. It is necessary to use a novel approach to the classification of AIM, approach, which based on the clinical features and immunological profile of the patients.
Nagaraju K et al. Inflammatory muscle disease: etiology and pathogenesis. In Rheumatology, ELSEVIER, Canada; 2011: 1523-1535.
Bohan A, Peter J. Polymyositis and dermatomyositis. N Engl J Med 1975, 292: 344-347; 403-407.
Troyanov Y et al. Novel classification of idiopathic inflammatory myopathies based on overlap syndrome features an autoantibodies. Medicine 2005, 84: 231-249.
Disclosure of Interest None declared