ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 0154

Anti-SMN Autoantibodies in Mixed Connective Tissue Disease Are Associated with a Scleromyositis Phenotype

Hajar El Kamouni1, Alexandra Albert2, Sabrina Hoa3, Darya S. Jalaledin4, Josiane Bourre-Tessier5, Eric Rich5, Jean-Richard Goulet6, Martial Koenig7, Minoru Satoh8, Marvin Fritzler9, May Choi10, Yves Troyanov11, Jean-Luc Senécal5 and Océane Landon-Cardinal5, 1Division of Rheumatology, Centre Hospitalier de l'Université de Montréal, Laval, Canada, 2Division of Rheumatology, Centre Hospitalier de l'Université Laval, Québec, QC, Canada, 3University of Montreal, Montréal, QC, Canada, 4Division of Internal Medicine, Centre Hospitalier de l'Université de Sherbrooke, Saint-Lambert, Canada, 5Division of Rheumatology, Centre Hospitalier de l'Université de Montréal, Montréal, QC, Canada, 6Division of Rheumatology, Centre Hospitalier de l'Université de Montréal, Saint-Lambert, Canada, 7Division of Internal Medicine, Centre Hospitalier de l'Université de Montréal, Montréal, QC, Canada, 8Department of Human, Information and Science, University of Occupational Environmental Health, Kitakyusyu Fukuoka, Japan, 9University of Calgary, Calgary, AB, Canada, 10Brigham and Women's Hospital | University of Calgary, Calgary, AB, Canada, 11Division of Rheumatology, Hôpital du Sacré-Coeur de Montréal, Montréal, QC, Canada

Meeting: ACR Convergence 2022

Keywords: , , ,

Session Information

Date: Saturday, November 12, 2022

Title: Muscle Biology, Myositis and Myopathies Poster I

Session Type: Poster Session A

Session Time: 1:00PM-3:00PM

Background/Purpose: The survival of motor neuron (SMN) is a ubiquitous macromolecular complex, located in the Cajal body of mammalian nuclei, with an essential role in assembly of small nuclear RNPs. Recent data have described autoantibodies (aAbs) to the SMN complex as novel biomarkers in scleromyositis, and as a potential biomarker for severe small bowel involvement in anti-U1RNP+ myositis patients. The aim of this study was to compare phenotypic features of Mixed Connective Tissue Disease (MCTD) patients with and without anti-SMN aAbs.

Methods: Anti-U1RNP+ MCTD patients from a previously clinically and serologically described retrospective cohort were studied. Patients fulfilling ≥ 1 MCTD classification of Alarcon-Segovia (AS), Kasukawa (Ka), Kahn (Kn) and/or Tanaka (Ta) were included. An addressable laser bead immunoassay utilizing a full-length recombinant human protein was used to detect specific anti-SMN aAbs with normal reference range of < 300 mean fluorescence intensity (MFI) to classify 300-999 MFI as low-titer and ≥ 1000 MFI as high-titer positivity.

Clinical features were assessed for the presence of ACR/EULAR and non ACR/EULAR features of systemic sclerosis (SSc), systemic lupus erythematosus (SLE), Sjögren syndrome (SS) and myositis. Comparisons among anti-SMN+ and anti-SMN- subgroups used Fisher two-tailed exact test. Logistic regression analyses (univariable and multivariable adjusted for sex, age at diagnosis and disease duration) with 95% confidence intervals performed on outcomes of interest.

Results: Sixty-six patients were included and MCTD criteria were respectively fulfilled in 86% (AS), 73% (Ka), 97% (Kn) and 98% (Ta) patients. Fifty-eight patients (88%) were females and median age at MCTD diagnosis was 41 years (range 11–70 years). At last follow-up (median duration 12 years), 71%, 81% and 12% of 66 patients fulfilled the ACR/EULAR criteria for SSc, SLE and SS, respectively. Thirty-nine of 66 (59%) patients were positive for anti-SMN aAbs: 10 (26%) had low-titer and 29 (74%) had high-titer anti-SMN, based on highest available titer during follow-up.The presence of anti-SMN aAbs in MCTD patients was associated with a higher risk of fingertip pitting scars (23% anti-SMN+ vs 4% anti-SMN-, p=0.04), lower gastrointestinal (GI) involvement (defined as pneumatosis and/or pseudoobstruction and/or small intestinal bacterial overgrowth)

(26% vs 4%, p=0.039), myositis (37% vs 15%, p=0.09), and myocarditis (16% vs 0%, p=0.037).

On multivariable logistic regression, the risk of myositis or lower GI involvement was highest among patients with high-titer anti-SMN: adjusted OR 4.30 (95% CI, 1.11-19.86, p=0.04) and 11.99 (95% CI, 1.82-248.08, p=0.03), respectively.

The combined outcome of pitting scars and/or lower GI involvement and/or myositis and/or myocarditis was highest among those with high-titer anti-SMN: adjusted OR 7.79 (2.33-30.45, p=0.002).

Conclusion: Anti-SMN aAbs were present in 59% of patients in this criteria-defined MCTD cohort. The presence of anti-SMN aAbs, especially with high titers, were associated with a higher prevalence of myositis and SSc features, i.e., scleromyositis, compared to patients without anti-SMN aAbs.

Disclosures: H. El Kamouni, None; A. Albert, None; S. Hoa, None; D. S. Jalaledin, None; J. Bourre-Tessier, None; E. Rich, None; J. Goulet, None; M. Koenig, None; M. Satoh, None; M. Fritzler, Mitogen Diagnostics Corporation; M. Choi, AstraZeneca, MitogenDx, mallinckrodt, Janssen, AbbVie/Abbott, Alimentiv, Amgen, AVIR Pharma Inc, BioJAMP, Bristol-Myers Squibb(BMS), Celltrion, Ferring, Fresenius Kabi, McKesson, Mylan, Takeda, Pendopharm, Pfizer, Roche; Y. Troyanov, None; J. Senécal, None; O. Landon-Cardinal, None.

To cite this abstract in AMA style:

El Kamouni H, Albert A, Hoa S, S. Jalaledin D, Bourre-Tessier J, Rich E, Goulet J, Koenig M, Satoh M, Fritzler M, Choi M, Troyanov Y, Senécal J, Landon-Cardinal O. Anti-SMN Autoantibodies in Mixed Connective Tissue Disease Are Associated with a Scleromyositis Phenotype [abstract]. Arthritis Rheumatol. 2022; 74 (suppl 9). https://acrabstracts.org/abstract/anti-smn-autoantibodies-in-mixed-connective-tissue-disease-are-associated-with-a-scleromyositis-phenotype/. Accessed .

« Back to ACR Convergence 2022

ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-smn-autoantibodies-in-mixed-connective-tissue-disease-are-associated-with-a-scleromyositis-phenotype/