Myotonic dystrophy symptoms
Fact-checked by Myotonic dystrophy is a multisystem genetic condition that can cause muscle weakness, muscle wasting, muscle pain (myalgia), and difficulty relaxing muscles after they contract (myotonia).
Because the disease affects multiple body systems, patients can experience issues with the heart, breathing, digestion, sleep, vision, hormone regulation, and brain function. Symptoms vary widely from person to person and differ between myotonic dystrophy type 1 (DM1) and type 2 (DM2). While the two types share several features, each exhibits distinct patterns of muscle involvement and other symptoms.
Recognizing and understanding these symptoms helps individuals track health changes, guide daily care, and inform clinical discussions.
What are the symptoms of myotonic dystrophy?
Myotonic dystrophy is a complex disorder that causes progressive muscle weakness and wasting. Affected individuals often experience difficulty relaxing muscles at will, making it challenging to release objects after gripping them.
The condition can also impair cardiac function, respiratory strength, gastrointestinal motility, sleep quality, visual acuity, and cognitive processing.
Symptoms vary considerably among patients and between DM1 and DM2. The table below outlines the primary body systems affected, along with common associated symptoms.
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| Body system | Possible myotonic dystrophy symptoms |
| Muscles | Muscle weakness, muscle wasting, stiffness, myotonia, pain, and fatigue |
| Heart | Abnormal heart rhythms and problems with the heart’s electrical conduction |
| Breathing | Respiratory muscle weakness |
| Sleep | Excessive daytime sleepiness, sleep apnea, difficulty sleeping, and restless legs |
| Digestive system | Difficulty swallowing, constipation, diarrhea, abdominal discomfort, gallstones, and other gastrointestinal problems |
| Eyes | Cataracts and other vision changes |
| Hormones and metabolism | Diabetes, insulin resistance (when the body does not respond normally to insulin), thyroid problems, and other changes involving hormones |
| Brain and behavior | Changes in thinking, planning, behavior, or emotions |
Early signs of myotonic dystrophy
Early signs of myotonic dystrophy can be subtle, leading patients to attribute them to aging, physical activity, or other conditions. Some individuals first notice difficulty relaxing their hands or legs, whereas others experience persistent muscle pain or fatigue years before obvious weakness develops.
In DM1, early symptoms may include difficulty releasing a grip, foot drop causing frequent tripping, or weakness affecting the hands, face, or neck.
Conversely, DM2 usually begins in adulthood, typically in the 20s or 30s. Initial DM2 features often include muscle pain, stiffness, and fatigue before weakness appears. DM2 weakness typically affects the proximal muscles, or those closest to the body’s center, such as those in the hips, thighs, neck, and shoulders.
Tracking new symptoms across multiple body systems — such as changes in gait, swallowing, vision, cardiac sensation, or digestion — can be useful before a medical appointment.
Muscle symptoms
Muscle problems are central to both DM1 and DM2, but the pattern can differ.
Myotonia and muscle stiffness
Myotonia occurs when a muscle takes longer than usual to relax after contracting. Patients may struggle to release a doorknob, unclench a hand, or relax leg muscles after walking. Myotonia can also impair tongue and jaw muscles, leading to slurred speech or chewing difficulties.
Muscle weakness and wasting
Progressive muscle weakness may eventually occur alongside localized muscle wasting. In DM1, weakness typically begins distally (hands, feet, lower legs, face, and neck), but proximal muscles may also become affected as the disease progresses.
In contrast, DM2 primarily affects the proximal muscles (hips, thighs, shoulders, and neck), making it difficult for patients to climb stairs, rise from chairs, or lift their heads. Unlike DM1, muscles in the extremities and face are rarely affected in DM2.
Muscle pain and fatigue
Patients frequently report muscle pain, which tends to be more widespread and disabling with DM2, occasionally growing severe enough to limit daily functioning. Fatigue may also develop alongside muscle weakness or sleep problems.
Swallowing and speech difficulties
Weakness in the muscles used for swallowing can make eating and drinking more difficult, causing patients to eat more slowly, cough during meals, or require fluids to clear food. Speech can also become impaired when myotonia or weakness affects the jaw, tongue, or other muscles involved in speaking.
Symptoms beyond the muscles
As a systemic condition, myotonic dystrophy can lead to nonmuscular symptoms.
Heart symptoms
Myotonic dystrophy can affect the heart’s electrical system, predisposing individuals to arrhythmias. Because heart abnormalities can remain asymptomatic yet be fatal, routine cardiac monitoring is essential for everyone with a myotonic dystrophy diagnosis.
Immediate medical evaluation is necessary if patients experience these symptoms, which may indicate an abnormal heart rhythm or another heart-related complication:
- fainting or dizzy spells
- new or severe palpitations
- chest discomfort
Breathing and sleep problems
Respiratory muscle weakness can occur, particularly in DM1. Patients also experience higher rates of sleep disorders, including sleep apnea, insomnia, nonrestorative sleep, and profound daytime sleepiness despite getting enough hours of sleep.
Digestive symptoms
Myotonic dystrophy can also affect the muscles that control the digestive tract, causing symptoms such as:
- difficulty swallowing
- constipation or diarrhea
- slowed gut motility
- abdominal cramps
- bloating
- gallstones
Digestive symptoms occur more frequently or are more noticeable in DM1, though DM2 can also cause significant digestive problems.
Eye symptoms
Cataracts may develop at an earlier age than in the general population. Specifically, DM2 is associated with posterior subcapsular cataracts, which form at the back part of the eye.
Hormonal and metabolic symptoms
Myotonic dystrophy can affect hormones, especially insulin, which cells need to take sugar from the bloodstream. Metabolic alterations include impaired insulin signaling, increasing the risk of insulin resistance and diabetes.
The disorder can also affect other types of hormones, leading to thyroid or reproductive hormone abnormalities.
Cognitive, behavioral, and emotional symptoms
Central nervous system involvement varies by disease type. Children with DM1 may have difficulties with attention, planning, learning, or behavior rather than noticeable muscle weakness. Adults with DM2 may experience difficulties with skills such as planning, organizing, managing tasks, and remembering information. However, intellectual disability is not considered a typical feature of DM2.
Myotonic dystrophy type 1 symptoms
DM1 has several subtypes categorized by age of onset and overall severity.
Mild and adult-onset DM1
Adult-onset DM1, sometimes called classic DM1, typically manifests during adolescence or adulthood. Patients experience myotonia along with slowly progressive weakness and wasting in distal muscles (hands and feet), leading to difficulty writing, using tools, or walking without tripping. Multisystem involvement can also affect cardiac function, respiration, swallowing, digestion, and vision.
Juvenile-onset DM1
Juvenile-onset DM1 begins before adolescence. Children may initially not have obvious muscular symptoms, instead displaying difficulties with learning, attention, planning, social interaction, or behavior. Muscle weakness and other typical features of DM1 may become more apparent with age.
Congenital myotonic dystrophy
Congenital DM1 is a form that is apparent at birth, with the newborn showing severe hypotonia (“floppy baby” appearance) and marked weakness. These newborns may require immediate respiratory and feeding support due to profound weakness of the respiratory and bulbar muscles needed for breathing, sucking, and swallowing. DM2 has no established congenital form.
Myotonic dystrophy type 2 symptoms
DM2 typically develops in adulthood, predominantly with proximal muscle weakness. Weakness in finger flexors or elbow extensors may develop later in the disease course. Associated systemic features include cataracts, heart rhythm problems, hormonal abnormalities, digestive problems, hearing impairment, sleep disturbances, and cognitive changes. Although DM2 is often considered less severe overall than DM1, symptoms and complications can vary widely. Muscle pain can be substantial, and patients can still develop significant heart or other complications affecting multiple body systems.
Differences between DM1 and DM2 symptoms
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| Feature | DM1 | DM2 |
| Typical onset | Can occur from infancy through adulthood | Usually adulthood |
| Main muscle pattern | More often affects muscles farther from the center of the body | More often affects muscles closer to the center of the body |
| Myotonia | Often more noticeable | Usually less pronounced |
| Muscle pain | Can occur | Often prominent and sometimes disabling |
| Congenital presentation | Has a congenital form | No established congenital form |
| Respiratory involvement | More common and potentially severe | Generally less severe |
| Digestive involvement | Common | Can occur, but generally milder |
| Overall pattern | Can range from mild to severe | Often milder than DM1, but significant complications can occur |
When to get urgent medical attention
Patients may need a prompt medical assessment if they develop symptoms that could indicate problems with their heart and breathing muscles.
Symptoms requiring urgent medical attention include:
- fainting or near-fainting
- new or severe palpitations
- chest discomfort
- severe or worsening shortness of breath
- choking
- significant difficulty breathing while asleep
- severe daytime sleepiness associated with suspected sleep-related breathing problems
Progression of myotonic dystrophy symptoms
Myotonic dystrophy is generally progressive, but the pace and pattern of progression can vary considerably from one person to another. DM1 can begin at different ages and cause distinct symptom patterns, whereas DM2 usually begins in adulthood and often progresses more gradually. Initial features like myotonia or weakness may precede systemic complications involving vision, cardiac function, digestion, or metabolism by years, underscoring the need for comprehensive ongoing multisystem monitoring.
Symptoms often appear gradually over time:
- Early signs may include muscle pain or difficulty walking.
- Later complications may involve the eyes, heart, digestion, or hormones.
Because myotonic dystrophy affects multiple body systems, tracking new health changes across the entire body, not just muscle strength, is key to managing care.
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