Extreme phenotypic variability in a German family with X-linked myotubular myopathy associated with E404K mutation in MTM1

Neuromuscul Disord. 2006 Nov;16(11):749-53. doi: 10.1016/j.nmd.2006.07.020. Epub 2006 Sep 26.


X-linked myotubular myopathy (XLMTM) is a congenital muscle disorder caused by mutations in the MTM1 gene. Affected males usually present at birth with severe hypotonia and respiratory insufficiency, and most of them die within the first few years of life. We report here on a 68-year-old patient with a very mild form of the disease who was diagnosed after his grandson showed muscular weakness and respiratory problems at birth. The E404K mutation in the MTM1 gene was found in both patients. To our knowledge, this grandfather is one of the oldest and most mildly affected known patients with an MTM1 mutation to date. Thus, this family represents a remarkable phenotypic variation of XLMTM ranging from a congenital to a mild adult form.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Child, Preschool
  • Exons / genetics
  • Female
  • Genetic Diseases, X-Linked / genetics*
  • Genetic Diseases, X-Linked / pathology
  • Germany
  • Humans
  • Infant
  • Male
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / physiopathology
  • Mutation / genetics*
  • Myopathies, Structural, Congenital / genetics*
  • Myopathies, Structural, Congenital / pathology
  • Pedigree
  • Phenotype*
  • Protein Tyrosine Phosphatases / genetics*
  • Protein Tyrosine Phosphatases, Non-Receptor
  • Whites / genetics


  • Protein Tyrosine Phosphatases
  • Protein Tyrosine Phosphatases, Non-Receptor
  • myotubularin