Miopatía Necrotizante Inmunomediada Asociada a Anticuerpos Anti-HMGCR en Paciente Pediátrico: Reporte de Caso

Matías Riquelme Venegas; Juan Barra Contreras; Diego Espinosa Núñez; Evelyn Núñez Cancino; Bárbara Stanley Villar

doi:10.5281/zenodo.23190421

Authors

Matías Riquelme Venegas Interno Medicina Universidad Andrés Bello Viña del Mar, Chile Author https://orcid.org/0009-0004-0119-4860
Juan Barra Contreras Interno Medicina Universidad Andrés Bello Viña del Mar, Chile Author https://orcid.org/0009-0009-4478-4728
Diego Espinosa Núñez Interno Medicina Universidad Andrés Bello Viña del Mar, Chile Author https://orcid.org/0009-0007-7407-9988
Evelyn Núñez Cancino Médico Pediatra, Reumatología Universidad de Chile, Santiago, Chile Author
Bárbara Stanley Villar Médico Pediatra, Reumatología Universidad Valparaíso, Viña del Mar, Chile Author https://orcid.org/0009-0000-8599-7599

DOI:

https://doi.org/10.5281/zenodo.23190421

Keywords:

immune-mediated necrotizing myopathy, muscle weakness, Anti-HMGCR

Abstract

Introduction: Immune-mediated necrotizing myopathy (IMNM) is a rare idiopathic inflammatory myopathy characterized by progressive muscle weakness, marked elevation of creatine kinase (CK), and muscle fiber necrosis with minimal inflammatory infiltrate. The presence of anti-HMGCR antibodies is associated with a specific subtype of the disease. Methodology: 7-year-old female patient presenting with alopecia, asthenia, and progressive motor impairment over a two-year period, associated with difficulty walking, rising from the floor, and performing daily activities. Laboratory tests revealed persistent elevation of CK levels, while muscle magnetic resonance imaging demonstrated diffuse muscular edema without fatty infiltration. Subsequently, high-titer anti-HMGCR antibodies (>200 U) were identified, establishing the diagnosis of anti-HMGCR-associated IMNM. Results: Treatment was initiated with methylprednisolone and intravenous immunoglobulin, followed by methotrexate as maintenance therapy. Discussion: This case is noteworthy due to the low frequency of anti-HMGCR-associated IMNM in the pediatric population and its slowly progressive course, with initially nonspecific manifestations that delayed early diagnostic suspicion. Conclusion: The identification of anti-HMGCR antibodies allowed appropriate diagnostic orientation and guided the initiation of an immunosuppressive regimen consistent with reports for this IMNM subtype. As no subsequent clinical follow-up was available, therapeutic response could not be assessed, which constitutes the main limitation of this report.

Keywords: immune-mediated necrotizing myopathy, muscle weakness, anti-HMGCR, Gowers’ sign, creatine kinase.

Downloads

Download data is not yet available.

References

1. Portela-Sánchez S, Catalina I, López Muñoz S, Lozano Ros A, Sánchez-Soblechero A, Sola Vendrel E, et al. Miopatía necrosante inmunomediada: experiencia en una unidad neuromuscular. Neurologia. 2025;40(8):729-738. Disponible en: http://doi.org/10.1016/J.NRL.2023.03.005

2. Plou S, Gaona M, Caputo V. Miopatía necrotizante autoinmune. Presentación de un caso clínico. Rev Argent Reumatol. 2021.

3. Khoo T, Lilleker JB, Thong BY-H, Leclair V, Lamb JA, Chinoy H. Epidemiology of the idiopathic inflammatory myopathies. Nat Rev Rheumatol. 2023;19(11):695-712. Disponible en: https://doi.org/10.1038/s41584-023-01033-0

4. Meyer A, Meyer N, Schaeffer M, Gottenberg JE, Geny B, Sibilia J. Incidence and prevalence of inflammatory myopathies: a systematic review. Rheumatology (Oxford). 2015;54(1):50-63. Disponible en: https://doi.org/10.1093/rheumatology/keu289

5. Ramirez P, Giglio A, Dominguez I, Garrido F, Gutierrez F. Snapshot of a decade: idiopathic inflammatory myopathies in Chile—a 10-year short report. J Clin Rheumatol. 2025;31(5):205-209. Disponible en: http://doi.org/10.1097/RHU.0000000000002230

6. Pinal-Fernández I, Casal-Dominguez M, Mammen AL. Immune-mediated necrotizing myopathy. Curr Rheumatol Rep. 2018;20(4):21. Disponible en: https://doi.org/10.1007/s11926-018-0732-6

7. Wang C-H, Liang W-C. Pediatric immune-mediated necrotizing myopathy. Front Neurol. 2023;14:1123380. Disponible en: https://doi.org/10.3389/fneur.2023.1123380

8. Cobo-Ibáñez T, Sánchez-Piedra C, Nuño-Nuño L, Castellví I, Carrión-Barberà I, Romero-Bueno F, et al. Myo-Spain: Registro de pacientes con miopatía inflamatoria idiopática de España. Metodología. Reumatol Clin (Engl Ed). 2022;18(5):253-259. Disponible en: http://doi.org/10.1016/j.reumae.2021.01.004

9. Schiappacasse-Poyanco G. Miopatías necrotizantes autoinmunes: reconocimiento como nuevo subgrupo de miopatía inflamatoria idiopática. Rev Chil Reumatol. 2023;35(2):44-45. Disponible en: https://doi.org/10.58450/rcr.v35i2.45

10. Skolka MP, Pinal-Fernandez I, Mammen AL, Liewluck T. Emerging atypical clinicopathological manifestations of immune-mediated necrotizing myopathy (IMNM). Neuromuscul Disord. 2025. Disponible en: https://doi.org/10.1016/j.nmd.2025.105363

11. Allenbach Y, Mammen AL, Benveniste O, Stenzel W. 224th ENMC International Workshop: Clinico-sero-pathological classification of immune-mediated necrotizing myopathies, Zandvoort, The Netherlands, 14-16 October 2016. Neuromuscul Disord. 2018;28(1):87-99. Disponible en: http://doi.org/10.1016/j.nmd.2017.09.016

12. Leclair V. Immune-mediated necrotizing myopathy [Internet]. The Myositis Association; 2025.