Medical jargon can be very daunting for those diagnosed with cnm / mtm. This page has been set up in order to provide simple explanations of the most commonly used terminology.

Thank you to Sharon E. Hesterlee, Ph.D., Director of Research Development at the Muscular Dystrophy Association and Members of the YAHOO Myotubular Myopathy Message Board for their help in compiling this page

Types of Inheritance


Medical Symptoms


Medical Procedures

Genetic Terms

  • Central Nuclei

Normally the nuclei (the control centers that contain the chromosomes) of mature muscle cells are found along the very edges of the muscle cells to make room for the dense mesh of proteins required for lengthening and contracting; however, very young cells (during fetal development), or cells that are undergoing regeneration, typically have nuclei located in the centers of the cells. Centronuclear Myopathy is so-named because many of an affected person's muscle cells may have centrally located nuclei well after birth.

  • Fibre-Type Predominance and / or Disproportion

    There are two basic sizes of muscle fibres: large (type 1) and small (type 2). The fibers can be differentiated by their staining properties. In muscles commonly biopsied, these fibres normally are found in a ratio of 1:2 for type 1 and type 2 fibres, respectively. In Centronuclear Myopathy, there are many more type 1 fibres than normal and these fibres are abnormally small.

  • Myotubularin

Defects in the gene for this protein account for the x-linked form of Myotubular Myopathy. The myotubularin protein is an enzyme whose function is required for proper development of muscle cells.

  • MYF6 (Myogenic Factor 6)

Defects in this gene are responsible for some cases of Autosomal Dominant Centronuclear Myotubular Myopathy. The MYF6 protein, like Myotubularin, is required for proper development of muscle.

Medical Assistance

Note: A Gastronomy Button is similar to a Gastronomy Tube but instead of a tube coming out of the abdomen, there is a round button. A feeding extension is hooked up to the button to transport nutrients inside.

Further terminology can be found in the Research Glossary at the Myotubular Trust website and in the glossary produced by the Muscular Dystrophy Campaign.

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