Myotonic Dystrophy Awareness: September 15th is myotonic dystrophy (DM) awareness day, so let’s take a dive into this topic and learn about myotonic dystrophy. Myotonic Dystrophy is also known as DM1 or DM2, proximal myotonic myopathy (PROMM), Steinert Disease, dystrophia myotonica types one and two.
Myotonic Dystrophy is a type of Muscular Dystrophy
Muscular Dystrophy is a group of medical conditions that affect the muscles of the body in various ways, depending on the sub-group of dystrophies. All of the muscular dystrophy types contribute negatively to health muscle development and maintenance. Most with muscular dystrophy will lose their ability to grow and/or maintain muscles that are required for activities of daily living.
Each form of muscular dystrophy is caused by genetic mutations, which can be either spontaneous or inherited. Spontaneous cases of muscular dystrophy is caused by a spontaneous genetic mutation, which can be passed on to children through the parents’ genetics — either in a dominant or passive gene.
Inherited muscular dystrophy on the other hand is not caused by a spontaneous gene mutation after conception, but is given by one or both parents through a pre-existing genetic mutation. The mutation can be passed along in autosomal dominant or recessive genes (non-X genetic material) or by an X chromosome. This particular disorder is not passed along with a Y chromosome.
What is Myotonic Dystrophy
Myotonic dystrophy is one of the most common type of adulthood muscle dystrophies and is characterized by progressive muscle weakness and wasting of muscles. As its name suggests, myotonic dystrophy presents with prolonged muscle contractions, which cause the sufferer to be unable to relax their muscles after engaging them. An example might be someone opening a door using a handle, but being unable to release the handle as their muscle contractions continue long after their brain has given the signal to release.
There are two types of myotonic dystrophy, categorized as type one and type two, with type one being more prominent. This disorder affects roughly one out of 8,000 worldwide, but just over two cases per 100,000 in Canada.
Type One (1) and Type Two (2) Myotonic Dystrophy
Type one myotonic dystrophy is caused by mutations to the DMPK gene and it is theorized that this mutation causes a miscommunication within the cells that is related to the proteins produced by the gene. This particular dystrophy affects the peripheral muscles primarily, such as those on the legs and arms.
DM 1: The resulting disease was known as Steinert disease and has even more subtypes, mostly focused on the age of onset:
Congenital-onset DM1 is present at birth and characterized by poor muscle tone, joint contractures (inability to move joints due to muscle rigidity), cognitive impairment, respiratory failure, developmental abnormalities, and poor feeding related to the suckle reflex being stunted by poor muscle tone.
Childhood or juvenile-onset DM1 as you may guess develops in childhood prior to adolescence. This myotonic dystrophy presents with behavioral concerns, myotonia, mood disorders, cardiac issues such as arrhythmias or cardiomyopathy, anxiety, cognitive concerns, and attention deficits.
Adult-onset DM1 begins to show after adolescence and may show up initially as muscle weakness that is progressive, myotonia, respiratory weakness, cardiac issues, cataracts, and at times it might even present cognitively.
Mild DM1 appears typically after the age of 40 and presents as myotonia, mild weakness, and cataracts. It can begin to show up in early adulthood, but can also show up in older ages.
Type two is cased by mutations in the CNBP gene:
Also known as proximal myotonic myopathy or PROMM, affects the proximal muscles, such as those closer to the center of the body, and is most often seen in those between the ages of 10 to 60-years-old. This type of myotonic dystrophy is often less severe a disease than the classic type one.
