GNE Myopathy as a Myofibrillar Myopathy: Potential Important Disease Mechanism Implied by Muscle Biopsy

J Clin Neuromuscul Dis. 2020 Dec;22(2):90-96. doi: 10.1097/CND.0000000000000317.

Abstract

We report a case of 2 sisters in their 20s with genetically confirmed UDP-N-acetylglucoasmine 2-epimerase/N-acetylmannosamine kinase myopathy along with muscle biopsy findings. Both patients described slowly progressive signs of distal-predominant weakness since adolescence that had been dismissed as "clumsiness." Exam and electrodiagnostic testing suggested a predominately distal myopathy. Muscle biopsy of the left tibialis anterior revealed rimmed vacuoles and, interestingly, also had characteristic features of a myofibrillar myopathy. Genetic testing confirmed a diagnosis of autosomal recessive GNE myopathy in both patients. GNE myopathy has not typically been considered a myofibrillar myopathy, but this case raises possibilities worthy of further exploration. It is possible that the unique combination of pathogenic alleles in GNE reported here has led to a novel form of GNE myopathy with muscle biopsy showing characteristic features of GNE myopathy and myofibrillar myopathy. The other possibility is that myofibrillar myopathy may be a more common feature of GNE myopathies than classically described.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Biopsy
  • Distal Myopathies / diagnosis*
  • Female
  • Humans
  • Muscle, Skeletal / pathology*
  • Mutation
  • Myopathies, Structural, Congenital / diagnosis*

Supplementary concepts

  • Distal myopathy, Nonaka type
  • Myofibrillar Myopathy