Systems Affected by Myotonic Dystrophy

Myotonic dystrophy is a highly variable disorder. Multiple systems can be affected, each with a range of possible symptoms. However, an affected individual will not experience issues with all, or even most, of the systems that can be involved.

 

Skeletal Muscle

Myotonia. Myotonia is the inability to relax a contracted muscle. The prolonged spasms and stiffness associated with myotonia can lead to trouble releasing grip on objects, difficulty rising from a sitting position, or a stiff, awkward gait.

Muscle weakness and wasting. Generalized muscle weakness, skeletal muscle loss, and chronic muscle pain are common, typically in distal muscle (hands, feet, and face) with myotonic dystrophy: DM1, and proximal muscle (neck, shoulders, hip flexors, and upper legs) with proximal myotonic myopathy: DM2, also known as PROMM.

Hypotonia. Newborns with the congenital form of myotonic dystrophy: DM1 often suffer from hypotonia (floppiness or rag doll appearance). These infants generally have very little movement of the face or body.

Heart

Abnormal heart rhythm. Problems with the electrical activity of the heart (cardiac conduction issues) can lead to an irregular heartbeat.

Heart muscle damage. Cardiac myopathy (heart muscle damage) can occur due to heart muscle wasting, excessive accumulation of fat and fibrous tissue, or enlargement of the heart muscle.

These cardiac issues can be serious and lead to life-threatening complications, even in asymptomatic individuals.

Breathing

Diaphragm and breathing muscle weakness. Myotonic dystrophy patients commonly have weakness of the diaphragm, abdominal muscle, and intercostal muscles (between the ribs) causing poor breathing force and resulting in low blood oxygen levels. Severe respiratory issues may require emergency medical attention.

Aspiration. Swallowing issues and weak coughing muscle can result in foreign material being inhaled into the lungs. The inhaled material (food and drink, saliva, nasal secretions, or stomach fluids) can injure the lungs, leading to chronic inflammation and pneumonia.

Sleep apnea. Individuals with decreased muscle tone and structural features that narrow airways are at high risk for obstructive sleep apnea. Individuals with apnea repeatedly pause their breathing while they sleep, lowering the levels of oxygen. In mild cases, the resulting low levels of oxygen and disrupted sleep can lead to excessive fatigue and morning headaches; in more serious cases, increased blood pressure, cardiac arrhythmia and fatal heart attacks may occur.

Congenital DM1: Infants with congenital myotonic dystrophy (where symptoms are present at birth) have a high risk of mortality caused by respiratory failure. These children require intensive clinical intervention to improve their chance of survival. Use of a ventilator for newborns is often required.

Note: The neuromuscular, cardiac, and respiratory symptoms of myotonic dystrophy result in elevated risk of complications associated with the use of anesthesia. Severe myotonic reactions and cardiac arrhythmias may result. Post operative pulmonary complications are also common. Please see  anesthesia guidelines for further information.

Cognitive Function

Cognitive issues. Intellectual development issues, including mild to moderate mental retardation and learning disabilities, may be seen in younger patients. Reduced executive function may occur later in life.

Psychological and behavioral issues. Psychosocial problems such as attention deficit hyperactivity, antisocial behavior, depression and anxiety disorders occur in some individuals, most commonly in later life.

Excessive daytime sleepiness. Excessive daytime sleepiness (EDS) is a hallmark of myotonic dystrophy and can be debilitating.

Gastrointestinal tract

Individuals with myotonic dystrophy often suffer from poor nutrition and weight loss. Swallowing problems, constipation and/or diarrhea, and chronic digestive system infections can cause significant abdominal pain.

Diagram from Myotonic Dystrophy - Present Management, Future Therapy, ed. P. Harper, B. van Engelen, B. Eymard, D. Wilcox, p. 116. Reprinted with permission from Oxford University Press

Vision

Individuals with myotonic dystrophy may experience cloudy or dimming vision caused by cataracts at younger ages than most people. Before the cataracts fully form as white lens opacities, eye doctors can often recognize a specific type of lens opacity characteristic of myotonic dystrophy (called posterior subcapsular iridescent cataracts). In rare cases, issues with the retina may also occur.

Immune System

Individuals with myotonic dystrophy may have reduced immune function caused by low levels of antibodies in the blood (hypogammaglobulinemia). There is inconclusive evidence as to whether these individuals have increased risk of respiratory infections, hearing loss, and certain types of cancer.

Hormone and Reproductive Systems

Individuals with myotonic dystrophy may not be able to respond to insulin properly, resulting in hyperglycemia (elevated blood sugar levels) and mild diabetic symptoms.

Low testosterone levels, frontal baldness, testicular failure and gonadal atrophy are seen in men with myotonic dystrophy.

Weakened uterine muscle that can interfere with normal delivery may present in female myotonic dystrophy patients. Further information on symptoms of pregnancy available under family planning.

 

Technical fact sheets are available which provide a more detailed description of the symptoms of myotonic dystrophy, as well as how these issues are diagnosed and treated. Please click here to link to the technical pdf pages.