Congenital myopathy with hanging big toe due to homozygous myopalladin (MYPN) mutation

Luciano Merlini, Patrizia Sabatelli, Manuela Antoniel, Valeria Carinci, Fabio Niro, Giuseppe Monetti, Annalaura Torella, Teresa Giugliano, Cesare Faldini, Vincenzo Nigro

Research output: Contribution to journalArticle

Abstract

BACKGROUND: Myopalladin (MYPN) is a component of the sarcomere that tethers nebulin in skeletal muscle and nebulette in cardiac muscle to alpha-actinin at the Z lines. Autosomal dominant MYPN mutations cause hypertrophic, dilated, or restrictive cardiomyopathy. Autosomal recessive MYPN mutations have been reported in only six families showing a mildly progressive nemaline or cap myopathy with cardiomyopathy in some patients.

CASE PRESENTATION: A consanguineous family with congenital to adult-onset muscle weakness and hanging big toe was reported. Muscle biopsy showed minimal changes with internal nuclei, type 1 fiber predominance, and ultrastructural defects of Z line. Muscle CT imaging showed marked hypodensity of the sartorius bilaterally and MRI scattered abnormal high-intensity areas in the internal tongue muscle and in the posterior cervical muscles. Cardiac involvement was demonstrated by magnetic resonance imaging and late gadolinium enhancement. Whole exome sequencing analysis identified a homozygous loss of function single nucleotide deletion in the exon 11 of the MYPN gene in two siblings. Full-length MYPN protein was undetectable on immunoblotting, and on immunofluorescence, its localization at the Z line was missed.

CONCLUSIONS: This report extends the phenotypic spectrum of recessive MYPN-related myopathies showing: (1) the two patients had hanging big toe and the oldest one developed spine and hand contractures, none of these signs observed in the previously reported patients, (2) specific ultrastructural changes consisting in Z line fragmentation, but (3) no nemaline or caps on muscle pathology.

Original languageEnglish
Pages (from-to)1-7
Number of pages7
JournalSkeletal Muscle
Volume9
Issue number1
DOIs
Publication statusPublished - May 27 2019

Keywords

  • Cardiomyopathy
  • Congenital muscular dystrophy
  • Contractures
  • Hanging big toe
  • Myopalladin (MYPN)
  • Z line

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    Merlini, L., Sabatelli, P., Antoniel, M., Carinci, V., Niro, F., Monetti, G., Torella, A., Giugliano, T., Faldini, C., & Nigro, V. (2019). Congenital myopathy with hanging big toe due to homozygous myopalladin (MYPN) mutation. Skeletal Muscle, 9(1), 1-7. https://doi.org/10.1186/s13395-019-0199-9