Idiopatic inflammatory myopathies: serological and clinical correlations. Analysis of a monocentric series

Abstract

Objectives. To correlate the serological data obtained with line blot kits for myositis specific antibodies (MSA) and myositis associated antibodies (MAA) with clinical and instrumental data of a monocentric series of patients with idiopathic inflammatory myopathies (MII). Methods. Sera from 60 patients (related to the clinic dedicated to MII) were tested with the EUROIMMUNE Myositis Profiles 3 and 4 kits, which are in vitro qualitative tests allowing the determination of human IgG autoantibodies directed against 16 different specific antigens: Mi-2α, Mi-2β, TIF1, MDA5, NPX2, SAE1, Ku, PM-Scl 100, PM-Scl 75, Jo-1, SRP, PL-7, PL-12, EJ, OJ, Ro52. Patients were then retrospectively evaluated for both demographic and clinical data (fever, Raynaud's phenomenon (FdR), arthritis, mechanics hand (MH), heliotrope rash, papules and sign Gottron, erythema, skin ulcers, sclerodactyly, neoplasia) at presentation. The presence of interstitial lung disease (ILD) was assessed by High resolution computed tomography (HRCT) (measured GOH score for the extension) and spirometry as Forced vital capacity (FVC) and Diffusing capacity (DLCO). Severe ILD was defined by: GOH score >20 and FVC and DLCO <75%. Summary of the results. Of the 60 patients studied 39 (65%) were females. Twelve (21.7%) were suffering from polymyositis (PM) and antisintetasis syndrome (ASS), 18 (30%) from dermatomyositis (DM), 3 (5%) from paraneoplastic PM, 4 (6.7%) from DM paraneoplastic, 3 (5%) from amyopatic DM, 5 (8.3%) from Scleromyositis, 1 from overlap (PM/systemic lupus erythematosus) whereas 2 had unclassifiable myositis. The MSA found were: Jo1 (15), Mi-2 (7), SRP (5), TIF1 (4), NPX2 (2), SAE (2), MDA5 (2), OJ (2), PL7 (1). The MAA were: Ku (3), Ro52 (12), PM-Scl (13). Five patients (8.3%) were positive for 2 or more MSA. The association between MSA and MAA, in particular between Jo1 and Ro52, was frequent (p <0.05). Jo-1, Mi-2, PM-Scl and SRP were associated with ASS, DM, amyopatic DM and PM, respectively (p <0.05). Severe ILD was associated with Jo-1 (p <0.05). Comparing the mean values, Jo-1, Ro 52 and PM-Scl positive (after eliminating Jo-1 positive from the comparison group for the last two antibodies) had GOH values basically higher and lower values of FVC and DLCO, at p <0.05 for GOH and FVC in Jo-1 and PM-Scl positive, and FVC in Ro52 positive. Patients Mi-2, SRP and TIF1 positive, were less affected by ILD with GOH values significantly lower (p <0.05) (see Table). TIF1 was associated with paraneoplastic DM (p <0.05) with a negative predictive value and positive, respectively of 94% and 75% (OR 44.25). Finally the following associations of antibody with clinics were detected (p <0.05): Jo1 with arthritis and MH, Ku with sclerodactyly and FdR, Mi-2 with erythema, MDA5 with skin ulcers. Concluding statements: MSA and MAA play an important role in diagnosis and prognostic stratification of patients with MII allowing to identify patients at higher risk of developing severe complications (cancer, ILD)