Myotonic dystrophy is a type of muscular dystrophy, the symptoms of which usually appear during adulthood, although they can show up at any age. It is an inherited condition characterized by progressive muscle wasting and loss of muscle strength.
Genetic causes of myotonic dystrophy
Myotonic dystrophy is diagnosed in two types. Type 1 (DM1) is caused by a mutation in the DMPK gene and primarily affects the muscles of the neck, face, lower legs, and hands. Type 2 (DM2) is caused by variations in the CNBP gene and is characterized by muscle weakness mainly in the shoulders, neck, hips, and elbows.
The specific function of these genes is unclear. The DMPK gene carries instructions to make dystrophia myotonica protein kinase, a protein that may have a role in cell-to-cell communication, especially in the brain, heart, and skeletal muscles. The CNBP gene encodes for CCHC-type zinc finger nucleic acid binding protein that is primarily found in the heart and skeletal muscles.