Ryanodine receptor 1 related myasthenia like myopathy responsive to pyridostigmine

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Disease causing variants in the Ryanodine receptor 1 (RYR1) gene are a common cause for congenital myopathy and for malignant hyperthermia susceptibility. We report a 17 year old boy with congenital muscle weakness progressing to a myasthenia like myopathy with muscle weakness, fatigability, ptosis, and ophthalmoplegia. Muscle biopsy showed predominance and atrophy of type 1 fibers. Whole-exome trio sequencing revealed three variants in the RYR1-gene in the patient: c.6721C > T,p.(Arg2241*) and c.2122G > A,p.(Asp708Asn) in cis position, and the c.325C > T,p.(Arg109Trp) variant in trans. Treatment with pyridostigmine improved symptoms. This case supports that a myasthenia like phenotype is part of the phenotypic spectrum of RYR1 related disorders, and that treatment with pyridostigmine can be beneficial for patients with this phenotype.

Original languageEnglish
Article number104706
JournalEuropean Journal of Medical Genetics
Issue number3
Publication statusPublished - Mar 2023


  • Malignant hyperthermia
  • Myasthenia
  • Ophthalmoplegia
  • RYR1 congenital myopathy
  • Ryanodine receptor calcium release channel
  • Therapeutics
  • Ryanodine Receptor Calcium Release Channel/genetics
  • Humans
  • Muscle Weakness/genetics
  • Male
  • Muscle, Skeletal/pathology
  • Phenotype
  • Pyridostigmine Bromide/therapeutic use
  • Adolescent
  • Mutation
  • Muscular Diseases/genetics


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