AB0251 CLINICAL FEATURES OF KOREAN PATIENTS WITH ANTI-SRP ANTIBODY-ASSOCIATED IMMUNE-MEDIATED NECROTIZING MYOPATHY (2024)

Abstract

Background: Immune-mediated necrotizing myopathy (IMNM) is a subgroup of inflammatory myopathy characterized by subacute proximal weakness and prominent myofiber necrosis with minimal inflammatory cell infiltrate in muscle biopsies. The two principle categories of IMNM, anti-signal recognition particle (SRP) autoantibodies-IMNM and anti-3-hydroxy-3-methylglutaryl-coa reductase autoantibodies-IMNM, currently account for the largest proportion of IMNM and have been extensively described.

Objectives: To understand the characteristics of Korean patients with anti-SRP IMNM, we measured anti-SRP antibodies and analyzed the clinical features of patients with anti-SRP antibody-associated IMNM.

Methods: We measured titers of anti SRP antibody in the sera of 84 patients with inflammatory myopathy and 107 healthy subjects using an enzyme-linked immunosorbent assay. Clinical data were obtained retrospectively by reviewing medical records. Clinical information included assessments of the age at symptom onset, disease duration, muscle impairments, dysphagia, dysarthria, dyspnea, skin lesions, cardiomyopathy interstitial lung disease, cancers, and treatment regimens. Laboratory analyses included the serum creatine kinase (CK) level.

Results: Positivity for the anti-SRP antibody was observed in 20 (8 males and 12 females) of 50 patients with IMNM. Anti-SRP antibody was negative in patients with inclusion body myositis (0/9), patients with polymyositis (0/11), patients with dermatomyositis (0/14), and 107 healthy subjects. The median age at symptom onset and disease duration of Korean patients with anti-SRP antibody were 43 years (interquartile range: 6.3 – 59.3 years) and 3 months (interquartile range: 2 – 12 months), respectively. The most common symptoms were symmetric proximal muscle weakness in 20 patients (100%), dysphagia in 5 (25%), dyspnea in 3 (15%), and dysarthria in 2 (10%). There was one patient each with dilated cardiomyopathy and interstitial lung disease, but here was no patient with cancer. The median CK level was 8404.5 IU/l (interquartile range: 4535.3 – 10025.5 IU/l). The median titer of anti-SRP antibody was 2.8 IU/ml (interquartile range: 1.6 – 12.4 IU/ml).

Conclusion: Our study was the first to measure anti-SRP antibodies in Korean patients with inflammatory myopathy and to analyze the clinical features of patients with anti-SRP antibody-associated IMNM.

Acknowledgements: I would like to thank the patients for their help with this work.

Disclosure of Interests: None declared.