Myopathy

Disease Description (Causes and Symptoms)

• Definition summary: Myopathy is a group of diseases characterized by progressive loss of muscle strength due to structural and functional abnormalities of skeletal muscle, which may affect motor function, breathing, and cardiac function. It may occur due to congenital (genetic) or acquired (inflammatory, metabolic, toxic, etc.) causes.
• Main causes: Genetic mutations (e.g., dystrophin deficiency), inflammatory diseases (polymyositis, dermatomyositis), metabolic abnormalities (e.g., deficiency of enzymes in the Pompe-related pathway), endocrine abnormalities, drug or toxin exposure, etc.
• Pathophysiology summary: Depending on the cause, degeneration and necrosis of muscle fibers, deposition of fat and connective tissue (pseudohypertrophy), infiltration of inflammatory cells, and impaired energy production may occur, weakening the muscle fibers.
• Main symptoms:
  • Progressive muscle weakness (especially proximal muscle weakness: the thighs and shoulders)
  • Easy fatigue and falls, difficulty climbing stairs
  • Calf pseudohypertrophy (deposition of fat and connective tissue)
  • Joint contractures (shortening of muscles and tendons), scoliosis
  • Ptosis (drooping eyelids), dysphagia (difficulty swallowing)
  • Muscle cramps and pain (in some types), difficulty breathing (weakness of the respiratory muscles)
  • Heart failure and arrhythmias when the cardiac muscle is involved

Treatment Methods

• General principles: A multidisciplinary approach is needed that combines disease-specific treatment based on the cause (genetic, inflammatory, metabolic, etc.) with management of symptoms and complications (pediatric rehabilitation, pulmonology, cardiology, orthopedics, neurology/genetics, nutrition, psychology, etc.).
• Standard treatment by cause (examples):
  • Hereditary muscular dystrophy (e.g., Duchenne): Corticosteroids (used to delay progression in severe disease), consideration of some gene-targeted treatments (such as exon skipping), and clinical trial treatments.
  • Inflammatory myopathies (polymyositis and dermatomyositis): High-dose steroids, immunosuppressants (such as methotrexate and azathioprine), IVIG, or biologic agents.
  • Metabolic myopathies (e.g., Pompe): Disease-specific treatments such as enzyme replacement therapy (e.g., alglucosidase).
• Treatment of symptoms and complications:
  • Physical therapy and exercise therapy: Prevention of joint contractures, maintenance of muscle strength and endurance, and functional training (including respiratory rehabilitation).
  • Respiratory management: Regular monitoring with pulmonary function tests, consideration of nocturnal noninvasive ventilation (NIV), cough-assist devices, and recommended preventive vaccines (influenza and pneumococcal vaccines).
  • Cardiac management: Regular echocardiography and electrocardiography; ACE inhibitors, beta-blockers, antiarrhythmic drugs, etc., may be used if cardiomyopathy develops.
  • Orthopedic treatment: Surgical correction may be considered for progressive scoliosis or severe contractures.
  • Nutritional and swallowing management: Dietary modification or nasogastric tube feeding may be considered if dysphagia is severe.
  • Rehabilitation and occupational therapy: Maintenance of activities of daily living (ADL) and use of assistive devices (walkers, wheelchairs, etc.).
• Precautions (points to note)
  • Some myopathies may carry an increased risk of complications during anesthesia or when certain medications are used, so prior consultation with anesthesiology and neurology is necessary before surgery.
  • During long-term steroid use, side effects such as osteoporosis, weight gain, and diabetes must be monitored.
  • As respiratory muscle weakness progresses, there is a risk of acute respiratory failure, so early evaluation and response are necessary.
• Prevention and lifestyle management
  • Regular respiratory rehabilitation and cough-assist practice, improving the home environment to prevent falls, nutritional management, and regular cardiac and respiratory evaluations.
  • Receiving recommended vaccinations to prevent infectious complications.

Checklist Before an Outpatient Visit (Items to Prepare and Example Questions)

• Materials/items to bring:
  • List of currently used medications and supplements (including doses and administration times)
  • Past test results (including electromyography, CK/muscle enzyme levels, genetic test results, muscle biopsy reports, echocardiography and pulmonary function test results, etc.)
  • Record of symptom changes (when they began, which area was affected first, aggravating and relieving factors)
  • Activity limitations and use of assistive devices (walker, wheelchair, photographs of assistive devices, etc.)
  • Sleep- and breathing-related symptoms (difficulty breathing at night, daytime sleepiness, symptoms of sleep apnea)
  • Family history (muscle weakness or similar symptoms)
• Items the healthcare professional may ask about (examples of frequently asked questions):
  • When the symptoms first began and how they have progressed
  • Activities that are difficult in daily life (climbing stairs, brushing teeth, etc.)
  • Whether swallowing difficulties are present (choking while swallowing, weight loss)
  • Whether shortness of breath or nighttime breathing problems are present

Examples of General Questions to Ask the Doctor

• "What are the possible causes of this disease? What additional tests are needed?"
• "What treatment options are currently recommended, and what benefits and side effects can be expected?"
• "If respiratory muscle weakness progresses, what signs should I watch for, and when should noninvasive ventilation be started?"
• "Are there any activities I should avoid in daily life or types of exercise that are recommended?"
• "What is the usual prognosis (long-term function and survival) for this type?"

Examples of Disease-Specific Questions

• If a hereditary cause is suspected: "What is the diagnostic significance of the variant found in the genetic test, and is family testing (cascade testing) needed?"
• When respiratory or cardiac involvement is suspected: "Cardiac and pulmonary function decline is suspected. How often should regular tests be performed, and what treatments and preventive measures are needed?"

(Note: Diagnosis and treatment vary depending on the individual patient's condition and disease type. Please consult the treating healthcare professionals for a specific diagnosis and treatment plan.)