Anti-MJ/NXP-2 autoantibody specificity in a cohort of adult Italian patients with polymyositis/dermatomyositis
1 Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA
2 Rheumatology Unit, A.O. Spedali Civili, Piazzale Spedali Civili 1, 25123, Brescia, Italy
3 Division of Rheumatology and Clinical Immunology, Department of Medicine; Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610-0221, USA
Arthritis Research & Therapy 2012, 14:R97 doi:10.1186/ar3822Published: 30 April 2012
Autoantibodies in patients with polymyositis/dermatomyositis (PM/DM) are associated with unique subsets, clinical course and outcome. Anti-MJ antibodies, which recognize the nuclear protein NXP-2/MORC3, are reported in ~25% of juvenile DM. Prevalence and clinical significance of anti-MJ antibodies in adult Italian PM/DM patients were studied.
Sera from 58 consecutive adult Italian PM/DM patients were analyzed by immunoprecipitation of 35S-labeled K562 cells extract, ELISA (anti-MJ, Jo-1), Western blot and indirect immunofluorescence. Clinical associations were analyzed using information from medical charts.
Anti-MJ antibodies were the most prevalent specificity (17%) found mainly in DM (30%, 8 cases) vs 8% of PM (2 cases, P = 0.02). Comparing 10 anti-MJ (+) vs 48 anti-MJ (-) cases, DM was more common (P = 0.03), and age at onset was younger in anti-MJ (+) (P = 0.0006). In anti-MJ (+), heliotrope rash (P = 0.01) and calcinosis (P = 0.09) were more frequent. None of them had heart or lung involvement, or malignancy. Myopathy in anti-MJ (+) patients responded well to therapy and none of them had elevated CPK at last visit (0% vs 25% in anti-MJ (-)). Only 60% of anti-MJ (+) showed immunofluorescent nuclear dots staining, despite PML localization of NXP-2/MORC3.
Anti-MJ antibodies are the most frequent specificity in our cohort of adult Italian PM/DM. Anti-MJ (+) were associated with young onset DM, calcinosis, no internal organ involvement and good response of myopathy to therapy. Anti-MJ reported in juvenile DM is also found in adult PM/DM, and could be a new useful biomarker.