Longitudinal Course of the Disease in Anti-Mi2 Patients: More Intense Muscle Weakness, Good Response to Treatment and Progressive Reduction of Autoantibody Titers

Iago Pinal-Fernandez^1,2, Katherine Pak³, Maria Casal-Dominguez^4,5, Wilson Huang⁴, Jemima Albayda⁶, Eleni Tiniakou⁷, Julie J. Paik¹, Christopher A. Mecoli⁸, Sonye K. Danoff⁹, Lisa Christopher-Stine⁹ and Andrew Mammen^3,10, ¹Rheumatology, Johns Hopkins University School of Medicine, Baltimore, MD, ²Muscle Diseases Unit, National Institute of Arthritis and Musculoskeletal and Skin Diseases. National Institutes of Health, Bethesda, MD, ³National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, ⁴NIAMS, NIH, Bethesda, MD, ⁵Johns Hopkins Medical School, Baltimore, MD, ⁶Johns Hopkins University School of Medicine, Baltimore, MD, ⁷Division of Rheumatology, Johns Hopkins University School of Medicine, Baltimore, MD, ⁸Internal Medicine/Rheumatology, Johns Hopkins University, Baltimore, MD, ⁹Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, ¹⁰Center Tower Ste 5300, Johns Hopkins University School of Medicine, Baltimore, MD

Meeting: 2018 ACR/ARHP Annual Meeting

Keywords: autoantibodies, autoantigens, dermatomyositis, muscle strength and myositis

Session Information

Date: Tuesday, October 23, 2018

Session Title: Muscle Biology, Myositis and Myopathies Poster III: Treatment and Classification Criteria

Session Type: ACR Poster Session C

Session Time: 9:00AM-11:00AM

Background/Purpose:

Autoantibodies targeting the Mi-2 (Mi-2a and Mi-2b) nuclear antigen in patients with dermatomyositis (DM) were first described in 1985. However, little is known about the phenotype and evolution of disease over time in these patients compared to anti-Mi2-negative DM patients. The objective of this project was to address the clinical features and the evolution of autoantibody titers over time in DM patients with anti-Mi2 autoantibodies compared to anti-Mi2-negative DM patients and other forms of myositis.

Methods:

In this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up were compared between anti-Mi2-positive patients and patients with anti-Mi2-negative DM, the antisynthetase syndrome (AS), and immune-mediated necrotizing myopathy (IMNM). The evolution of the anti-Mi2 autoantibody titers were also studied in those patients with available longitudinal sera.

Results:

Sixty-two anti-Mi2-positive DM, 160 anti-Mi2-negative DM, 168 AS, and 183 IMNM patients were included in this study. Anti-Mi2-positive patients had more severe proximal muscle weakness and increased muscle enzyme levels both at disease onset and during follow-up compared to anti-Mi2-negative DM (all p<0.001) or AS patients (all p<0.01). Anti-Mi2-positive DM patients were stronger compared to those with IMNM (all p<0.01). Unlike those with IMNM, younger anti-Mi2-positive patients were stronger at disease onset compared to older anti-Mi2-positive patients (p=0.005). Calcinosis and myalgia were less common in anti-Mi2-positive than in anti-Mi2-negative DM patients. Anti-Mi2-positive patients were generally responsive to first-line immunosuppressant treatment; after two years of follow-up, most of them had recovered full strength. Ninety-two percent (11/12) of anti-Mi2-positive patients had decreases in autoantibody titers during the first 3 years of follow-up; 25% (3/12) of them had normalization anti-Mi2 autoantibodies during follow-up.

Conclusion:

Although anti-Mi2-positive DM patients are initially weaker than anti-Mi2-negative DM patients, both groups generally respond well to treatment with recovery of muscle strength. With treatment, anti-Mi2 autoantibody titers decrease and may even normalize.

Disclosure: I. Pinal-Fernandez, None; K. Pak, None; M. Casal-Dominguez, None; W. Huang, None; J. Albayda, None; E. Tiniakou, None; J. J. Paik, None; C. A. Mecoli, None; S. K. Danoff, None; L. Christopher-Stine, None; A. Mammen, None.

To cite this abstract in AMA style:

Pinal-Fernandez I, Pak K, Casal-Dominguez M, Huang W, Albayda J, Tiniakou E, Paik JJ, Mecoli CA, Danoff SK, Christopher-Stine L, Mammen A. Longitudinal Course of the Disease in Anti-Mi2 Patients: More Intense Muscle Weakness, Good Response to Treatment and Progressive Reduction of Autoantibody Titers [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 10). https://acrabstracts.org/abstract/longitudinal-course-of-the-disease-in-anti-mi2-patients-more-intense-muscle-weakness-good-response-to-treatment-and-progressive-reduction-of-autoantibody-titers/. Accessed August 24, 2019.

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