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Anti-MJ/NXP-2 antibodies are the most common specifcity in a cohort of adult caucasian patients with dermatomyositis
  1. Angela Ceribelli1,
  2. Micaela Fredi2,
  3. Mara Taraborelli2,
  4. Ilaria Cavazzana3,
  5. Franco Franceschini3,
  6. Angela Tincani2,
  7. Steven J Ross1,
  8. Brad A Pauley1,
  9. Edward K L Chan1,
  10. Minoru Satoh1
  1. 1Division of Rheumatology and Clinical Immunology, Department of Medicine, University of Florida, Gainesville, Florida, USA
  2. 2Rheumatology Unit, University of Brescia and Spedali Civili, Brescia, Italy
  3. 3Rheumatology Unit, University of Brescia, Brescia, Italy

Abstract

Background/objective Specific autoantibodies in patients with polymyositis/dermatomyositis (PM/DM) are associated with unique subsets, and they are useful in monitoring clinical course and predicting outcome. Anti-MJ antibodies, which recognise the nuclear protein NXP-2 in PML (promyelocytic leukemia) nuclear bodies, are a new specificity reported in 23–25% of juvenile DM, usually associated with severe muscle atrophy, functional impairment, and calcinosis. The aim of our study is to analyse the prevalence and clinical significance of anti-MJ antibodies in a cohort of adult Caucasian PM/DM patients.

Methods Autoantibodies in sera from 58 consecutive adult PM/DM patients (74% female, mean age 43+/−17, mean follow-up 55 months) were analysed by immunoprecipitation of 35S-labeled K562 cell extracts, ELISA (anti-MJ, Ro52, La, Jo-1), Western Blot and Indirect Immunofluorescence (IIF). Clinical association of anti-MJ was analysed using information from charts and database.

Results Anti-MJ antibodies are the most prevalent specificity (10/58; 17%) in our PM/DM cohort, followed by anti-Jo-1 (10%), -p155/140 (5%), -SRP (5%), -EJ (4%) and anti-Mi-2, -SMN complex, -OJ with one case each. Anti-MJ was found in 30% of DM and 8% of PM (p: 0.02). Among 10 cases of anti-MJ, 8 were DM and 2 were PM. When clinical features of 10 cases of anti-MJ (+) versus 48 cases anti-MJ (-) were compared, DM is more common (p: 0.03) and no overlap syndrome patients were found in anti-MJ group (0% vs 13%). Age of onset (25.5 vs 46.1 years) and age at initial visit (37.6 vs 54.6 years) were younger in anti-MJ group (p: 0.002), and 2 anti-MJ (+) were pediatric onset DM. In anti-MJ (+) patients, heliotrope rash (p:0.01) and calcinosis (p:0.057) were common, however, none of them had heart involvement (0% vs 27%, p:0.03), interstitial lung disease (0% vs 33%, p:0.048), or cancer (0% vs 8%). Myopathy in anti-MJ (+) patients showed a good response to steroid therapy. Only 6/10 anti-MJ (+) showed PML body nuclear dots staining in IIF, suggesting that IIF cannot be used for screening of anti-MJ antibodies.

Conclusion Anti-MJ antibodies are detected also in adult PM/DM, and they are the most frequent specificity in our cohort, found in 17% of PM/DM (30% in DM and 8% in PM). Anti-MJ (+) patients showed DM of young onset with a mild myopathy, severe calcinosis and without internal organ involvement. Anti-MJ will be a useful new addition of myositis-associated autoantibodies to help clinical monitoring of patients with adult PM/DM.

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