Date: Monday, November 9, 2020
Session Type: Poster Session D
Session Time: 9:00AM-11:00AM
Background/Purpose: Myositis are characterized by weakness and muscle inflammation. They encompass heterogeneous conditions, which include dermatomyositis (DM), inclusion body myositis (IBM) and polymyositis (PM) according to the EULAR/ACR 2017 criteria. We recently recorded a high prevalence of IBM in a cohort of primary Sjögren’s syndrome (SS). Our objective was to refine the signification of SS in the setting of myositis.
Methods: Among a monocentric myositis cohort (according to the EULAR/ACR 2017 criteria), SS patients (according to the ACR/EULAR 2016 criteria) were identified (myositis/SS+ group) and compared to myositis patients without SS (myositis/SS- group).
Results: Among 417 myositis patients, SS criteria were available for 99 patients. Thirty-four (34%) presented SS. Patients with SS tended to be more frequently women (F/M ratio 10.3 vs 3.1, p = 0.058). Age at diagnosis of myositis was similar in both groups (53 years [range 21-74] vs 53 years [range 16-77], p = 0.45).
Myositis subtypes repartition (as defined by EULAR/ACR 2017 criteria) was different in myositis/SS+ and myositis/SS- groups (p = 0.020), IBM being four-fold more prevalent in myositis/SS+ group (24% vs 6%, p = 0.020). Accordingly, the delay between the first muscle symptoms and myositis diagnosis was longer in myositis/SS+ group (6 months [0-336] vs 4 months [0-122], p = 0.057). Moreover, aside anti-cN1A antibodies, myositis-specific antibodies were less frequently found in myositis/SS+ patients than in myositis/SS- ones (53% vs 72%, p = 0.054).
Anti-cN1A antibodies were more prevalent in myositis/SS+ patients (38% vs 6%, p = 0.0005). However, in myositis/SS+ group, anti-cN1A were frequent in each of the EULAR/ACR 2017 myositis subtypes and the association between SS and anti-cN1A positivity was maintained in a multivariate analysis taking into account the diagnosis of IBM (p = 0.020).
Specificity of anti-cN1A for IBM was 0.96 [95% CI, 0.87 – 0.99] in the myositis/SS- group but dropped to 0.70 [95% CI, 0.48 – 0.85] in the myositis/SS+ group.
9 (26%) of the myositis/SS+ patients had systemic involvement typical of SS (vs 5 [7%] of the myositis/SS- patients, p = 0.11) including polyneuropathy (8 [24%] vs 5 [8%]) and type 2 cryoglobulinaemic vasculitis (1 [3%] vs none). In addition, 2 (6%) myositis/SS+ patients developed a lymphoma (one B diffuse large cell lymphoma of the parotid and one non-Hodgkin lymphoma), vs none of the myositis/SS- patients (p = 0.11). 2 (6%) of the myositis/SS+ patients developed myositis-associated cancer (diagnosed within 3 years of myositis diagnosis) versus 6 (8%) of the myositis/SS- patients.
Aside hydroxychloroquine, more frequently used in myositis/SS+ group (38% vs 16%, p = 0.012), no significant difference was found in the management of the patients (taking into account the myositis subtype).
Conclusion: Myositis patients with SS have more frequently IBM (without response to immunomodulatory drugs) than myositis patients without SS. They also have more frequently anti-cN1A antibody, independently of IBM diagnosis.
To cite this abstract in AMA style:Lévy D, Nespola B, Giannini M, Felten R, Severac F, Varoquier C, Rinagel M, Korganow A, Poindron V, Martin T, Campagne J, Chereih H, Bouldoires B, Hervier B, Lenormand C, Chatelus E, Arnaud L, Gény B, Sibilia J, Gottenberg J, Meyer A. In Myositis Patients, Sjögren’s Syndrome Is Associated with Inclusion Body Myositis and with anti-cN1A Antibody Independently of the Myositis Subgroups [abstract]. Arthritis Rheumatol. 2020; 72 (suppl 10). https://acrabstracts.org/abstract/in-myositis-patients-sjo%cc%88grens-syndrome-is-associated-with-inclusion-body-myositis-and-with-anti-cn1a-antibody-independently-of-the-myositis-subgroups/. Accessed May 10, 2021.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/in-myositis-patients-sjo%cc%88grens-syndrome-is-associated-with-inclusion-body-myositis-and-with-anti-cn1a-antibody-independently-of-the-myositis-subgroups/