Novel variant in the PYGM gene causing late-onset limb-girdle myopathy, ptosis, and camptocormia

Muscle Nerve. 2018 Jan;57(1):157-160. doi: 10.1002/mus.25588. Epub 2017 Mar 21.

Abstract

Introduction: McArdle disease is a glycogen storage disease caused by mutations in the PYGM gene encoding myophosphorylase. It manifests classically with childhood-onset exercise-induced pain.

Methods: We report the characteristics of 2 unrelated patients with a new homozygous mutation of the PYGM gene.

Results: Two patients, aged 76 and 79 years, presented with severe upper and lower limb atrophy and weakness. Additionally, 1 patient presented with bilateral ptosis, and the other with camptocormia. In both patients, symptoms had developed progressively in the 2 preceding years, and there was no history of exercise intolerance. Both patients demonstrated myogenic abnormalities on electromyography, multiple glycogen-containing vacuoles and undetectable muscle myophosphorylase activity on muscle biopsy, and a novel homozygous frameshift p.Lys42Profs*48 PYGM mutation.

Conclusions: This report expands the phenotype and genotype of McArdle disease and suggests that PYGM mutations should be looked for in patients with very late-onset myopathy with no previous history of exercise intolerance. Muscle Nerve 57: 157-160, 2018.

Keywords: McArdle disease; PYGM; camptocormia; elderly; glycogen storage disease; myopathy.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Blepharoptosis / complications
  • Blepharoptosis / genetics*
  • Computer Simulation
  • Electromyography
  • Female
  • Glycogen Storage Disease Type V / genetics*
  • Humans
  • Male
  • Muscular Atrophy, Spinal / complications
  • Muscular Atrophy, Spinal / genetics*
  • Muscular Dystrophies, Limb-Girdle / complications
  • Muscular Dystrophies, Limb-Girdle / genetics*
  • Mutation / genetics
  • Spinal Curvatures / complications
  • Spinal Curvatures / genetics*

Supplementary concepts

  • Camptocormia