Muscle histopathology in myasthenia gravis with antibodies against MuSK and AChR

S. Martignago, M. Fanin, E. Albertini, E. Pegoraro, C. Angelini

Research output: Contribution to journalArticlepeer-review


Aims: We compared myopathological features in myasthenia gravis (MG) patients with antibodies against AChR (seropositive) and muscle-specific tyrosin-kinase (MuSK). While the immunopathogenesis of seropositive MG is well known, there is a lack of pathological studies in anti-MuSK antibody-positive (MuSK+) MG. Methods: We analysed skeletal muscle biopsy features of 13 MG patients: 6 MuSK+ (all women) and 7 anti-AchR antibody-positive (AChR+) (2 women and 5 men). In our histopathological examination, we quantified the atrophy factor of both fibre types, and the extent of minicores, myofibrillar disarray, cytochrome c oxidase (COX)-negative fibres, mitochondrial aggregates and fibre type grouping. Results: Mean muscle fibre atrophy factor was higher in AChR+ MG than MuSK+ MG, both in type I fibres (494 vs. 210) and particularly in type II fibres (1023 vs. 300). Fibre type grouping was observed in AChR+ MG whereas COX-negative fibres were common in MuSK+ MG. Bulbar muscles were more severely affected in MuSK+ MG and the disease was more severe: the onset was usually earlier (39 years) with Myasthenia Gravis Foundation of America score III in MuSK+ MG, and score II was found in AChR+ MG (62 years). Conclusions: Muscle biopsies of MuSK+ MG show myopathic signs with prominent mitochondrial abnormalities, whereas neurogenic features and atrophy are more frequently found in AChR+ MG. The mitochondrial impairment could explain the oculo-bulbar involvement in MuSK+ MG.

Original languageEnglish
Pages (from-to)103-110
Number of pages8
JournalNeuropathology and Applied Neurobiology
Issue number1
Publication statusPublished - Feb 2009


  • AChR
  • Antibodies
  • Muscle biopsy
  • Muscle-specific tyrosin-kinase
  • Myasthenia gravis

ASJC Scopus subject areas

  • Clinical Neurology
  • Pathology and Forensic Medicine
  • Neurology
  • Histology
  • Physiology (medical)


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