Trouble at the junction: When myopathy and myasthenia overlap

Muscle Nerve. 2019 Dec;60(6):648-657. doi: 10.1002/mus.26676. Epub 2019 Sep 10.


Although myopathies and neuromuscular junction disorders are typically distinct, their coexistence has been reported in several inherited and acquired conditions. Affected individuals have variable clinical phenotypes but typically display both a decrement on repetitive nerve stimulation and myopathic findings on muscle biopsy. Inherited causes include myopathies related to mutations in BIN1, DES, DNM2, GMPPB, MTM1, or PLEC and congenital myasthenic syndromes due to mutations in ALG2, ALG14, COL13A1, DOK7, DPAGT1, or GFPT1. Additionally, a decrement due to muscle fiber inexcitability is observed in certain myotonic disorders. The identification of a defect of neuromuscular transmission in an inherited myopathy may assist in establishing a molecular diagnosis and in selecting patients who would benefit from pharmacological correction of this defect. Acquired cases meanwhile stem from the co-occurrence of myasthenia gravis or Lambert-Eaton myasthenic syndrome with an immune-mediated myopathy, which may be due to paraneoplastic disorders or exposure to immune checkpoint inhibitors.

Keywords: congenital myasthenic syndrome; myasthenia gravis; myopathy; neuromuscular junction disorder, neuromuscular transmission; repetitive nerve stimulation.

Publication types

  • Review

MeSH terms

  • Cardiomyopathies / complications
  • Cardiomyopathies / pathology
  • Cardiomyopathies / physiopathology
  • Electrodiagnosis
  • Electromyography
  • Humans
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / physiopathology*
  • Muscular Diseases / complications
  • Muscular Diseases / pathology
  • Muscular Diseases / physiopathology*
  • Muscular Dystrophies / complications
  • Muscular Dystrophies / pathology
  • Muscular Dystrophies / physiopathology
  • Myasthenia Gravis / complications
  • Myasthenia Gravis / pathology
  • Myasthenia Gravis / physiopathology
  • Myasthenic Syndromes, Congenital / complications
  • Myasthenic Syndromes, Congenital / pathology
  • Myasthenic Syndromes, Congenital / physiopathology*
  • Myopathies, Structural, Congenital / complications
  • Myopathies, Structural, Congenital / pathology
  • Myopathies, Structural, Congenital / physiopathology
  • Myotonic Disorders / complications
  • Myotonic Disorders / pathology
  • Myotonic Disorders / physiopathology
  • Neural Conduction
  • Neuromuscular Junction / physiopathology*

Supplementary concepts

  • Myopathy, Myofibrillar, Desmin-Related