Myotonic dystrophy (DM) is the most common form of late-developing muscular dystrophy, with the disease usually appearing during patients’ 20s and 30s. Symptoms can vary significantly from patient to patient and even among those in the same family.
The condition is caused by abnormally expanded sections in the DMPK gene, known as DM1, or in the CNBP gene, known as DM2. These abnormally expanded sections in the genes can grow as the disease is passed from parent to child, so the disease typically becomes more unpredictable and increasingly severe from one generation to the next.
Due to the variation in symptoms, specific therapy plans are generally developed for each individual. There are, however, several general medical management strategies that can help the majority of DM patients. As there is no cure for DM, treatment is focused on maintaining patients’ quality of life.
Muscles used for breathing and coughing progressively weaken in many DM1 patients and a small proportion of DM2 patients. Breathing function should be examined frequently to look for issues preemptively.
Clinicians may recommend that affected patients use a bilevel positive airway pressure device (BiPAP) for breathing assistance, especially at night, and also during the daytime if needed. Cough assistance machines can assist in removing secretions that the patient may have difficulty clearing. Removing excess phlegm can help reduce the risk of infection.
Minimizing choking hazards
DM1 patients may experience muscle weakness in the throat, making it difficult to swallow. This increases the risk of inhaling and choking on food, saliva, and vomit. Patients may need to limit their diet to types of food and beverage that are easy to swallow. Specialized occupational therapists can work with patients to teach them how to swallow.
Gastrointestinal issues usually are limited to patients with DM1. As the condition can affect the smooth muscles of the intestine, patients may experience constipation and develop gallstones. Laxatives, suppositories, or enemas may be prescribed to relieve constipation. If patients experience frequent pain due to gallstones, surgery to remove the gallbladder may be recommended.
Both DM1 and DM2 patients are at risk of developing heart abnormalities, including an abnormal heart rhythm, known as an arrhythmia, and weakening of the heart muscle, known as cardiomyopathy. However, these issues are more common among DM1 patients. Patients should have frequent electrocardiogram and echocardiogram tests to keep an eye on the heart rhythm and heart functionality, respectively.
Cardiologists may use pharmaceuticals, such as beta blockers and anti-arrhythmic drugs, and medical devices, such as pacemakers, to manage arrhythmia. Pharmaceuticals also may be recommended to reduce stress on the heart in patients who develop cardiomyopathy.
DM patients, especially DM1 patients, are more at risk for complications when put under general anesthesia. Patients should be sure to let the surgical team know about their condition, as the only way to mitigate the risk for anesthesia complications is careful monitoring of cardiac and respiratory function.
Both DM1 and DM2 patients frequently develop opaque areas on the lens of the eye, known as cataracts. Ophthalmologists often will be included in the DM clinical team to test for and manage developing eye issues. Cataracts can be removed surgically, typically as an outpatient procedure, if they start to interfere with vision.
Skeletal muscle management
DM1 tends to cause initial muscle atrophy in the face, tongue, neck, hands, and feet. Occupational therapists may recommend a cane, walker, or ankle-foot orthosis, and eventually a wheelchair, to improve motility and reduce the risk of falls. Devices to assist in hand positioning, for writing or typing, may be used to help patients maintain independence.
Muscle weakness associated with DM2 is first noticed in the thighs, hips, and shoulders. Walking aids and wheelchairs also may be recommended to these patients. Pain, due to skeletal muscle atrophy, is more common in DM2 patients. Typically, discomfort can be alleviated with over-the-counter pain medications, heating pads, and massage.
Physical therapy and occupational therapy are typically included in treatment plans to maintain flexibility and reduce muscle atrophy. Occupational therapists will focus on improving muscle function required for daily life, such as walking and completion of fine motor skills with hands and fingers.
Myotonia, or the inability to relax muscles at will, is common in both forms of DM. If symptoms interfere with daily life, the effects of myotonia can be reduced with prescription drugs.
Medical management of congenital DM
DM1 also can develop from birth, in which case it is called congenital DM. Babies with this condition tend to experience the most severe symptoms of all DM patients. Feeding tubes and a ventilator may be necessary very soon after birth to help these babies until respiratory muscles and muscles used for sucking grow stronger.
Babies with congenital DM may experience more extreme muscle weakness, delaying sitting, standing, and walking milestones. Their feet may point downward and inward due to muscle atrophy during development. When babies develop this so-called “clubfoot,” casting or surgery often is needed to allow the child to learn to walk.
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