Background: Immune-mediated necrotizing myopathy (IMNM) is a distinct entity with limited large-cohort data. We aimed to characterize clinico-serological features and treatment outcomes of anti-SRP, anti-HMGCR, and seronegative IMNM in a large Italian cohort. Methods: Retrospective multicenter study of adults diagnosed with IMNM (224th ENMC criteria) across 14 Italian neuromuscular centers between 2019 and 2022 was performed. Results: We included 159 subjects (57% female, median age 62 years): 40 SRP+, 71 HMGCR+, 41 seronegative, and 7 untested. SRP+ more frequently presented with proximal upper limb weakness and axial involvement versus HMGCR+ (OR = 3.89, padj = 0.007, OR = 3.47, padj = 0.04) and seronegative (OR = 4.00, padj = 0.014, OR = 15.2, padj = 0.005). Lung involvement was higher in SRP+ (7.5%), vs none in HMGCR+ and 2.4% in seronegative (p=0.028). Extramuscular features were more frequent in HMGCR+ (OR = 3.78, p = 0.019, padj = 0.057). SRP+ had higher odds of loss of motor independence (OR=4.22, padj =0.011) and relapse (OR = 14.4, padj = 0.010) than HMGCR+. Seronegative had better functional outcomes than SRP+ (p=0.047). Cancer associated myositis predicted worse disability (OR = 6.93, p = 0.0044). Overall, 71.7% improved with corticosteroids (OR=3.83, padj =0.01) and immunosuppressants (OR=2.296, padj =0.037), without serotype differences. CK decreased in 81.8% and normalized in 40.3% of patients; ΔCK was associated with improvement (p=0.017), clinical remission (p=0.002) and correlated with post-treatment functional scores (R=0.19, p= 0.044). Conclusion: Subtype-specific differences and prognostic factors emerge. Exploratory functional assessment and ΔCK may capture treatment response in real-world settings.
Bonanno, S., Salvi, E., Cheli, M., Salerno, F., Lucchini, M., Cicia, A., Carlomagno, V., Lauletta, A., Tufano, L., Girolamo, F., De Gaetano, L. N., Fornaro, M., Pancheri, E., Zaottini, F., Faedo, E., Querini, P. R., De Lorenzo, R., Scarlato, M., Bottazzi, F., Riguzzi, P., Gibertini, S., Risi, B., Pugliese, A., Zoppi, D., Ruggiero, L., Ricci, G., Manganotti, P., Siciliano, G., Rodolico, C., Filosto, M., Bello, L., Pegoraro, E., Cavagna, L., Previtali, S. C., Fiorillo, C., Grandis, M., Vattemi, G., Tonin, P., Iannone, F., Antonini, G., Garibaldi, M., Mirabella, M., Maggi, L., Immune-mediated necrotizing myopathies: clinico-serological features and treatment outcomes of a large Italian cohort of patients, <<JOURNAL OF NEUROLOGY>>, 2026; 273 (9): N/A-N/A. [doi:10.1007/s00415-026-14089-1] [https://hdl.handle.net/10807/345636]
Immune-mediated necrotizing myopathies: clinico-serological features and treatment outcomes of a large Italian cohort of patients
Lucchini, Matteo;Cicia, Alessandra;Carlomagno, Vincenzo;Mirabella, Massimiliano;
2026
Abstract
Background: Immune-mediated necrotizing myopathy (IMNM) is a distinct entity with limited large-cohort data. We aimed to characterize clinico-serological features and treatment outcomes of anti-SRP, anti-HMGCR, and seronegative IMNM in a large Italian cohort. Methods: Retrospective multicenter study of adults diagnosed with IMNM (224th ENMC criteria) across 14 Italian neuromuscular centers between 2019 and 2022 was performed. Results: We included 159 subjects (57% female, median age 62 years): 40 SRP+, 71 HMGCR+, 41 seronegative, and 7 untested. SRP+ more frequently presented with proximal upper limb weakness and axial involvement versus HMGCR+ (OR = 3.89, padj = 0.007, OR = 3.47, padj = 0.04) and seronegative (OR = 4.00, padj = 0.014, OR = 15.2, padj = 0.005). Lung involvement was higher in SRP+ (7.5%), vs none in HMGCR+ and 2.4% in seronegative (p=0.028). Extramuscular features were more frequent in HMGCR+ (OR = 3.78, p = 0.019, padj = 0.057). SRP+ had higher odds of loss of motor independence (OR=4.22, padj =0.011) and relapse (OR = 14.4, padj = 0.010) than HMGCR+. Seronegative had better functional outcomes than SRP+ (p=0.047). Cancer associated myositis predicted worse disability (OR = 6.93, p = 0.0044). Overall, 71.7% improved with corticosteroids (OR=3.83, padj =0.01) and immunosuppressants (OR=2.296, padj =0.037), without serotype differences. CK decreased in 81.8% and normalized in 40.3% of patients; ΔCK was associated with improvement (p=0.017), clinical remission (p=0.002) and correlated with post-treatment functional scores (R=0.19, p= 0.044). Conclusion: Subtype-specific differences and prognostic factors emerge. Exploratory functional assessment and ΔCK may capture treatment response in real-world settings.
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