Myotonic Dystrophy

 
A higher resolution pdf file is available for download.

A higher resolution pdf file is available for download. See the link at the end of this article.

My wife had myotonic dystrophy. It was the underlying cause of her early death. Although we knew of her condition for the past 7 years, we were unaware just how life-threatening it could be. Unfortunately, her doctors were also ill informed since myotonic dystrophy is not a common illness. I am presenting some information here in the hopes that it could be useful, and even life extending, for others who may have myotonic dystrophy.

Myotonic dystrophy is caused by a defect in a specific area of chromosome 19 called DMPK (dystrophia myotonica-protein kinase).  It is normal for protein sequences to repeat a few times, however when a particular sequence in this region repeats more than 35 times, a person is said to be affected by myotonic dystrophy. This was discovered in the early 1990s and since then, suspected cases can be confirmed by a genetic test. Myotonic dystrophy is an inherited disease. It is passed from parent to child in an autosomal dominant fashion. This means that if one parent has the disease, their offspring each have a 50% chance of also being affected. Moreover, the disease tends to become worse with each successive generation. Thus, if a parent had a mild form of the disease, their child could have a classic or even a congenital form.

Myotonic dystrophy is classified based on the number of times the protein sequence is repeated. Fewer than 35 repeats–normal, no disease indicated. 35 -100 repeats–mildly affected by myotonic dystrophy. (However, their offspring have a 50% chance of developing the illness, possibly in a stronger form.) 100 – 1000 repeats–the person has the classic form of myotonic dystrophy. Beth had 212 repeats and was seriously affected..

Until 1992, myotonic dystrophy was one of many neuromuscular diseases that was difficult to diagnose with certainty. Since that time, the availability of genetic testing means that a person can be determined to either have the disease or not. Unfortunately, having this diagnostic capability for such a short time means that there have been many undiagnosed cases and therefore there are large numbers of people today who may be at risk for the illness and not know it. In my wife’s case, we will never know for certain which of her parents had the disease, although we are fairly certain it must have been her mother. For those with the mild form, they may have a normal life span with little physical symptoms. The most typical symptom would be early-onset cataracts, the possibility of diabetes, and the typical myotonia (the inability to relax one’s grip easily).

For those with the classic form, there are many symptoms affecting various muscles and organs. These include weakening of muscles in the forearms and hands, calves and feet, shoulders back and face, and diaphragm. Those weaknesses can affect a person’s ability to walk, keep their balance, perform fine motor skills with hands, and breathe. Men may experience infertility. Women with this form of myotonic dystrophy frequently have difficulty with childbirth. (My wife suffered through many hours of unproductive labor before eventually giving birth via cesarean section to our first child.)

Waiting for our daughter to arrive.  Myotonic dystrophy, not yet diagnosed, prevented natural delivery.

Waiting for our daughter to arrive. Myotonic dystrophy, not yet diagnosed, prevented natural delivery.

Weakness in the facial muscles can cause a person’s appearance to change rapidly. There can be loss of hair on the front of the scalp, drooping eyelids and an open mouth. These weaknesses can also cause frequent jaw dislocation, and difficulty swallowing.

Cataracts are very common, and an alert ophthalmologist can be the first to raise the possibility of myotonic dystrophy with the patient because the types of cataracts have a distinctive appearance when they are caused by myotonic dystrophy.

There is an increased likelihood of diabetes and cancer among those who have the classic form of myotonic dystrophy. They will also be more likely to have digestive and intestinal issues.

There are numerous hormonal consequences, including reduced sex drive, early infertility, insulin resistance, and thyroid problems. There can be increased chance of gallbladder inflammation, problems with the pancreas, and chronic constipation.

Beth overlooking the Grand Canyon and obviously not very steady on her feet. (Thank goodness for guardrails!) This was in 2004, one year before she was diagnosed with myotonic dystrophy. She was seeing doctors at this time but none of them could figure out why she had such poor balance.

Beth overlooking the Grand Canyon and obviously not very steady on her feet. (Thank goodness for guardrails!) This was in 2004, one year before she was diagnosed with myotonic dystrophy. She was seeing doctors at this time but none of them could figure out why she had such poor balance.

The most common causes of death for those with myotonic dystrophy are respiratory failure and cardiac arrest.  Most articles you will read about myotonic dystrophy recommend yearly EKGs because there is the likelihood that cardiac arrhythmia may develop. What they don’t say, is that there should also be a 24 hour Holter study done from time to time, as this is more likely to catch an arrhythmia that comes and goes. Thanks to having an autopsy performed following my wife’s death, we now know that she had been having episodes of insufficient blood flow to her brain for some time that had not been detected by either the annual EKG or MRIs. The MRIs would have shown more if we could have used contrast medium with her but unfortunately her kidneys had been damaged to the point where contrast medium was not possible. She died when a combination of factors overwhelmed her.

It is especially important that an anesthesiologist know about a patient’s status with myotonic dystrophy as the patient will be at much higher risk of respiratory issues.

Here are some things to look for:

An unusual walking gait where the foot seems to slap down on the ground, preventing the normal flowing motion of a healthy walking motion.  There may also be an increased likelihood of falling.

Early-onset cataracts, especially “Christmas Tree” cataracts on the back of the lens.

Difficulty relaxing ones grasp on an object.

Excessive sleepiness.

Download large format poster.

Important disclaimer: I am not a medical professional and what is on this page should not be considered medical advice. I have read a great deal about my wife’s illness and have attempted to presented the information in a more readable fashion here. I am providing you with the links to my sources. You should also know that I’m only covering the mild and classic forms of type I myotonic dystrophy. There is also the congenital form which can affect infants at birth and type II myotonic dystrophy where a different gene is affected and the disease is generally not as severe.

http://mda.org/sites/default/files/In_Focus_MMD.pdf
http://en.wikipedia.org/wiki/Myotonic_dystrophy
http://medicine.yale.edu/neurology/divisions/neuromuscular/md.aspx
http://ghr.nlm.nih.gov/condition/myotonic-dystrophy

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