Myopathy refers to diseases affecting the muscles, not caused by nerve or neuromuscular junction disorders. Causes can be diverse, but symptoms often include muscle weakness, reduced ability to carry out daily activities, and occasionally muscle pain or tenderness. Dark or discolored urine may indicate myoglobin in the urine.
In emergency care, distinguishing between muscular and neurological causes of weakness is essential. However, when severe weakness is present, priority should be given to stabilizing airway, breathing, and circulation, with precautions to prevent aspiration, while initiating supportive care and arranging inpatient evaluation.
Epidemiology
Myopathies are muscle disorders whose occurrence varies by type. Inflammatory and endocrine forms are relatively frequent, with inflammatory myopathies affecting about 2.4–33.8 per 100,000 individuals. Among inherited types, muscular dystrophies—especially Duchenne and Becker—are the most common, mainly in males, with an estimated prevalence of 19.8–25.1 per 100,000 person-years. Mitochondrial myopathies are rarer, affecting roughly 1 in 5,000 people.
Anatomy
Pathophysiology
Most congenital or inherited myopathies progress slowly over time and rarely require emergency treatment unless there is sudden worsening. In emergency settings, acute or subacute myopathies—such as those caused by metabolic, inflammatory, endocrine, or toxic factors—are encountered more frequently than congenital forms.
Periodic paralyses are disorders characterized by sudden muscle weakness due to potassium shifts, often linked to a genetic defect in the sodium ion channels of muscle cell membranes. Episodes can last from several hours to days.
Etiology
Idiopathic myopathies are immune-mediated muscle disorders that may occur alone or with connective tissue diseases such as SLE, RA, and polyarteritis nodosa, with examples including sarcoid myopathy, polymyositis, and dermatomyositis.
Alcohol-related myopathy can be acute—triggered by binge drinking, causing pain, limb weakness, and myoglobinuria with risk of renal injury—or chronic, leading to gradual hip and shoulder muscle wasting without myoglobinuria.
Other causes include infections (parasitic, viral, bacterial, and tick-borne), endocrine disorders (Addison’s, Cushing’s, thyroid, hyperparathyroidism), and drug or toxin exposure (e.g., corticosteroids, statins, zidovudine, cocaine, colchicine, amiodarone)
Periodic paralysis may be hypo-, hyper-, or normokalemic, with hypokalemic forms often familial or secondary to potassium loss or endocrine disease; attacks are triggered by diet, rest after exercise, or hormonal changes, and some cases resolve with treatment of the underlying cause.
Muscular dystrophies are inherited, progressive myopathies, with Duchenne being the most severe, affecting young boys and often involving cardiomyopathy. Other forms may affect both sexes and can lead to scoliosis, respiratory decline, infections, and worsening weakness.
Genetics
Prognostic Factors
The outlook for myopathies depends on their underlying cause, disease severity, and coexisting health conditions. In severe cases, profound muscle weakness can result in respiratory failure and death. Thyrotoxic hypokalemic periodic paralysis is more common in Asian men, with evidence suggesting increased risk among Polynesians as well.
Clinical History
Age Group:
Can occur at any age depending on etiology:
Inherited forms (e.g., muscular dystrophy, familial periodic paralysis) often present in childhood or adolescence.
Acquired forms (toxic, endocrine, inflammatory, metabolic) more common in adults.
Physical Examination
Assess and closely monitor airway status if respiratory muscle involvement is suspected.
Weakness is typically symmetrical and affects proximal muscle groups; muscle bulk is generally preserved in early stages.
Muscle tenderness is uncommon, and atrophy appears only in advanced disease.
Deep tendon reflexes and sensation are usually intact, though reflexes may be reduced or absent in hypokalemic paralysis.
Fever can be present, especially in cases of pyomyositis or polymyositis.
Mental status remains normal.
Age group
Associated comorbidity
Associated activity
Family history of muscular dystrophy or periodic paralysis.
Autoimmune diseases (e.g., SLE, RA), endocrinopathies (hyperthyroidism, hypothyroidism, Cushing’s), renal disease, or alcohol use disorder.
Medications: steroids, statins, antiretrovirals, colchicine, alcohol, PCP, heroin; higher risk with combination of myotoxic agents.
Triggers for periodic paralysis: high-carbohydrate meals, rest after exercise, exposure to cold.
Statin-related myopathy: physical activity as a precipitating factor.
Occupational/travel exposures: ingestion of absorbable barium salts from contaminated food or industrial sources.
Supportive care is central, especially in severe cases with respiratory compromise, cardiomyopathy, heart block, or aspiration risk. This may include airway monitoring, respiratory support, and measures to prevent aspiration.
Critical care monitoring is essential in rhabdomyolysis to manage complications such as acute kidney injury and electrolyte imbalances.
Dietary strategies may help in periodic paralysis:
In hyperkalemic periodic paralysis, some patients benefit from carbohydrate loading at the onset of symptoms to reduce attack severity.
In hypokalemic periodic paralysis, oral potassium-rich foods can help shorten attacks when swallowing is intact.
Activity modification—avoiding known triggers (e.g., prolonged rest after exercise, extreme cold exposure, or large high-carbohydrate meals in certain periodic paralyses).
Role of Oral potassium phosphate
Oral potassium supplementation can help shorten or reduce the severity of acute attacks, particularly since swallowing is generally unaffected. It offers a safer alternative to IV potassium, which should be used cautiously due to the risk of hyperkalemia. However, because episodes often resolve on their own within 4–24 hours, supplementation must be carefully monitored to avoid excessive potassium levels.
Airway and Respiratory Support: In severe myopathy with respiratory insufficiency or aspiration risk, procedural interventions such as endotracheal intubation and mechanical ventilation may be necessary to maintain oxygenation and protect the airway.
Cardiac Monitoring and Intervention: For associated cardiomyopathy or heart block, continuous cardiac monitoring is essential, and procedures like temporary pacemaker insertion may be required in severe conduction disturbances.
Critical Care Procedures in Rhabdomyolysis: Inpatient management may involve aggressive IV fluid resuscitation to prevent renal failure, and in severe cases of kidney injury, hemodialysis may be indicated to manage hyperkalemia and uremia.
IV Potassium Infusion: In hypokalemic periodic paralysis, cautiously administered IV potassium may be used when oral intake is not possible, with close monitoring to avoid hyperkalemia.
IV Glucose–Insulin Infusion: In hyperkalemic periodic paralysis, this procedure can help rapidly shift potassium into cells and reduce serum potassium levels.
use-of-phases-in-managing-myopathies
Management of myopathies can be approached in phases: an acute phase, focusing on stabilizing airway, breathing, and circulation, managing life-threatening complications (e.g., respiratory failure, arrhythmias, rhabdomyolysis), and addressing reversible triggers such as electrolyte imbalances; a subacute phase, aimed at targeted treatment of the underlying cause (e.g., immune modulation, endocrine correction, toxin withdrawal, or dietary adjustments for periodic paralysis); and a rehabilitation phase, emphasizing physiotherapy, occupational therapy, nutritional optimization, and long-term specialist follow-up to preserve muscle function and prevent complications.
Myopathy refers to diseases affecting the muscles, not caused by nerve or neuromuscular junction disorders. Causes can be diverse, but symptoms often include muscle weakness, reduced ability to carry out daily activities, and occasionally muscle pain or tenderness. Dark or discolored urine may indicate myoglobin in the urine.
In emergency care, distinguishing between muscular and neurological causes of weakness is essential. However, when severe weakness is present, priority should be given to stabilizing airway, breathing, and circulation, with precautions to prevent aspiration, while initiating supportive care and arranging inpatient evaluation.
Myopathies are muscle disorders whose occurrence varies by type. Inflammatory and endocrine forms are relatively frequent, with inflammatory myopathies affecting about 2.4–33.8 per 100,000 individuals. Among inherited types, muscular dystrophies—especially Duchenne and Becker—are the most common, mainly in males, with an estimated prevalence of 19.8–25.1 per 100,000 person-years. Mitochondrial myopathies are rarer, affecting roughly 1 in 5,000 people.
Most congenital or inherited myopathies progress slowly over time and rarely require emergency treatment unless there is sudden worsening. In emergency settings, acute or subacute myopathies—such as those caused by metabolic, inflammatory, endocrine, or toxic factors—are encountered more frequently than congenital forms.
Periodic paralyses are disorders characterized by sudden muscle weakness due to potassium shifts, often linked to a genetic defect in the sodium ion channels of muscle cell membranes. Episodes can last from several hours to days.
Idiopathic myopathies are immune-mediated muscle disorders that may occur alone or with connective tissue diseases such as SLE, RA, and polyarteritis nodosa, with examples including sarcoid myopathy, polymyositis, and dermatomyositis.
Alcohol-related myopathy can be acute—triggered by binge drinking, causing pain, limb weakness, and myoglobinuria with risk of renal injury—or chronic, leading to gradual hip and shoulder muscle wasting without myoglobinuria.
Other causes include infections (parasitic, viral, bacterial, and tick-borne), endocrine disorders (Addison’s, Cushing’s, thyroid, hyperparathyroidism), and drug or toxin exposure (e.g., corticosteroids, statins, zidovudine, cocaine, colchicine, amiodarone)
Periodic paralysis may be hypo-, hyper-, or normokalemic, with hypokalemic forms often familial or secondary to potassium loss or endocrine disease; attacks are triggered by diet, rest after exercise, or hormonal changes, and some cases resolve with treatment of the underlying cause.
Muscular dystrophies are inherited, progressive myopathies, with Duchenne being the most severe, affecting young boys and often involving cardiomyopathy. Other forms may affect both sexes and can lead to scoliosis, respiratory decline, infections, and worsening weakness.
The outlook for myopathies depends on their underlying cause, disease severity, and coexisting health conditions. In severe cases, profound muscle weakness can result in respiratory failure and death. Thyrotoxic hypokalemic periodic paralysis is more common in Asian men, with evidence suggesting increased risk among Polynesians as well.
Age Group:
Can occur at any age depending on etiology:
Inherited forms (e.g., muscular dystrophy, familial periodic paralysis) often present in childhood or adolescence.
Acquired forms (toxic, endocrine, inflammatory, metabolic) more common in adults.
Assess and closely monitor airway status if respiratory muscle involvement is suspected.
Weakness is typically symmetrical and affects proximal muscle groups; muscle bulk is generally preserved in early stages.
Muscle tenderness is uncommon, and atrophy appears only in advanced disease.
Deep tendon reflexes and sensation are usually intact, though reflexes may be reduced or absent in hypokalemic paralysis.
Fever can be present, especially in cases of pyomyositis or polymyositis.
Supportive care is central, especially in severe cases with respiratory compromise, cardiomyopathy, heart block, or aspiration risk. This may include airway monitoring, respiratory support, and measures to prevent aspiration.
Critical care monitoring is essential in rhabdomyolysis to manage complications such as acute kidney injury and electrolyte imbalances.
Dietary strategies may help in periodic paralysis:
In hyperkalemic periodic paralysis, some patients benefit from carbohydrate loading at the onset of symptoms to reduce attack severity.
In hypokalemic periodic paralysis, oral potassium-rich foods can help shorten attacks when swallowing is intact.
Activity modification—avoiding known triggers (e.g., prolonged rest after exercise, extreme cold exposure, or large high-carbohydrate meals in certain periodic paralyses).
Oral potassium supplementation can help shorten or reduce the severity of acute attacks, particularly since swallowing is generally unaffected. It offers a safer alternative to IV potassium, which should be used cautiously due to the risk of hyperkalemia. However, because episodes often resolve on their own within 4–24 hours, supplementation must be carefully monitored to avoid excessive potassium levels.
Airway and Respiratory Support: In severe myopathy with respiratory insufficiency or aspiration risk, procedural interventions such as endotracheal intubation and mechanical ventilation may be necessary to maintain oxygenation and protect the airway.
Cardiac Monitoring and Intervention: For associated cardiomyopathy or heart block, continuous cardiac monitoring is essential, and procedures like temporary pacemaker insertion may be required in severe conduction disturbances.
Critical Care Procedures in Rhabdomyolysis: Inpatient management may involve aggressive IV fluid resuscitation to prevent renal failure, and in severe cases of kidney injury, hemodialysis may be indicated to manage hyperkalemia and uremia.
IV Potassium Infusion: In hypokalemic periodic paralysis, cautiously administered IV potassium may be used when oral intake is not possible, with close monitoring to avoid hyperkalemia.
IV Glucose–Insulin Infusion: In hyperkalemic periodic paralysis, this procedure can help rapidly shift potassium into cells and reduce serum potassium levels.
Management of myopathies can be approached in phases: an acute phase, focusing on stabilizing airway, breathing, and circulation, managing life-threatening complications (e.g., respiratory failure, arrhythmias, rhabdomyolysis), and addressing reversible triggers such as electrolyte imbalances; a subacute phase, aimed at targeted treatment of the underlying cause (e.g., immune modulation, endocrine correction, toxin withdrawal, or dietary adjustments for periodic paralysis); and a rehabilitation phase, emphasizing physiotherapy, occupational therapy, nutritional optimization, and long-term specialist follow-up to preserve muscle function and prevent complications.
Myopathy refers to diseases affecting the muscles, not caused by nerve or neuromuscular junction disorders. Causes can be diverse, but symptoms often include muscle weakness, reduced ability to carry out daily activities, and occasionally muscle pain or tenderness. Dark or discolored urine may indicate myoglobin in the urine.
In emergency care, distinguishing between muscular and neurological causes of weakness is essential. However, when severe weakness is present, priority should be given to stabilizing airway, breathing, and circulation, with precautions to prevent aspiration, while initiating supportive care and arranging inpatient evaluation.
Myopathies are muscle disorders whose occurrence varies by type. Inflammatory and endocrine forms are relatively frequent, with inflammatory myopathies affecting about 2.4–33.8 per 100,000 individuals. Among inherited types, muscular dystrophies—especially Duchenne and Becker—are the most common, mainly in males, with an estimated prevalence of 19.8–25.1 per 100,000 person-years. Mitochondrial myopathies are rarer, affecting roughly 1 in 5,000 people.
Most congenital or inherited myopathies progress slowly over time and rarely require emergency treatment unless there is sudden worsening. In emergency settings, acute or subacute myopathies—such as those caused by metabolic, inflammatory, endocrine, or toxic factors—are encountered more frequently than congenital forms.
Periodic paralyses are disorders characterized by sudden muscle weakness due to potassium shifts, often linked to a genetic defect in the sodium ion channels of muscle cell membranes. Episodes can last from several hours to days.
Idiopathic myopathies are immune-mediated muscle disorders that may occur alone or with connective tissue diseases such as SLE, RA, and polyarteritis nodosa, with examples including sarcoid myopathy, polymyositis, and dermatomyositis.
Alcohol-related myopathy can be acute—triggered by binge drinking, causing pain, limb weakness, and myoglobinuria with risk of renal injury—or chronic, leading to gradual hip and shoulder muscle wasting without myoglobinuria.
Other causes include infections (parasitic, viral, bacterial, and tick-borne), endocrine disorders (Addison’s, Cushing’s, thyroid, hyperparathyroidism), and drug or toxin exposure (e.g., corticosteroids, statins, zidovudine, cocaine, colchicine, amiodarone)
Periodic paralysis may be hypo-, hyper-, or normokalemic, with hypokalemic forms often familial or secondary to potassium loss or endocrine disease; attacks are triggered by diet, rest after exercise, or hormonal changes, and some cases resolve with treatment of the underlying cause.
Muscular dystrophies are inherited, progressive myopathies, with Duchenne being the most severe, affecting young boys and often involving cardiomyopathy. Other forms may affect both sexes and can lead to scoliosis, respiratory decline, infections, and worsening weakness.
The outlook for myopathies depends on their underlying cause, disease severity, and coexisting health conditions. In severe cases, profound muscle weakness can result in respiratory failure and death. Thyrotoxic hypokalemic periodic paralysis is more common in Asian men, with evidence suggesting increased risk among Polynesians as well.
Age Group:
Can occur at any age depending on etiology:
Inherited forms (e.g., muscular dystrophy, familial periodic paralysis) often present in childhood or adolescence.
Acquired forms (toxic, endocrine, inflammatory, metabolic) more common in adults.
Assess and closely monitor airway status if respiratory muscle involvement is suspected.
Weakness is typically symmetrical and affects proximal muscle groups; muscle bulk is generally preserved in early stages.
Muscle tenderness is uncommon, and atrophy appears only in advanced disease.
Deep tendon reflexes and sensation are usually intact, though reflexes may be reduced or absent in hypokalemic paralysis.
Fever can be present, especially in cases of pyomyositis or polymyositis.
Supportive care is central, especially in severe cases with respiratory compromise, cardiomyopathy, heart block, or aspiration risk. This may include airway monitoring, respiratory support, and measures to prevent aspiration.
Critical care monitoring is essential in rhabdomyolysis to manage complications such as acute kidney injury and electrolyte imbalances.
Dietary strategies may help in periodic paralysis:
In hyperkalemic periodic paralysis, some patients benefit from carbohydrate loading at the onset of symptoms to reduce attack severity.
In hypokalemic periodic paralysis, oral potassium-rich foods can help shorten attacks when swallowing is intact.
Activity modification—avoiding known triggers (e.g., prolonged rest after exercise, extreme cold exposure, or large high-carbohydrate meals in certain periodic paralyses).
Oral potassium supplementation can help shorten or reduce the severity of acute attacks, particularly since swallowing is generally unaffected. It offers a safer alternative to IV potassium, which should be used cautiously due to the risk of hyperkalemia. However, because episodes often resolve on their own within 4–24 hours, supplementation must be carefully monitored to avoid excessive potassium levels.
Airway and Respiratory Support: In severe myopathy with respiratory insufficiency or aspiration risk, procedural interventions such as endotracheal intubation and mechanical ventilation may be necessary to maintain oxygenation and protect the airway.
Cardiac Monitoring and Intervention: For associated cardiomyopathy or heart block, continuous cardiac monitoring is essential, and procedures like temporary pacemaker insertion may be required in severe conduction disturbances.
Critical Care Procedures in Rhabdomyolysis: Inpatient management may involve aggressive IV fluid resuscitation to prevent renal failure, and in severe cases of kidney injury, hemodialysis may be indicated to manage hyperkalemia and uremia.
IV Potassium Infusion: In hypokalemic periodic paralysis, cautiously administered IV potassium may be used when oral intake is not possible, with close monitoring to avoid hyperkalemia.
IV Glucose–Insulin Infusion: In hyperkalemic periodic paralysis, this procedure can help rapidly shift potassium into cells and reduce serum potassium levels.
Management of myopathies can be approached in phases: an acute phase, focusing on stabilizing airway, breathing, and circulation, managing life-threatening complications (e.g., respiratory failure, arrhythmias, rhabdomyolysis), and addressing reversible triggers such as electrolyte imbalances; a subacute phase, aimed at targeted treatment of the underlying cause (e.g., immune modulation, endocrine correction, toxin withdrawal, or dietary adjustments for periodic paralysis); and a rehabilitation phase, emphasizing physiotherapy, occupational therapy, nutritional optimization, and long-term specialist follow-up to preserve muscle function and prevent complications.
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