Acquired non-inflammatory myopathy

A group of muscle diseases not caused by inflammation

Acquired non-inflammatory myopathy refers to a group of muscle diseases characterized by muscle weakness and dysfunction that are not caused by inflammation. These conditions can result from a variety of causes, including metabolic disorders, toxins, and genetic factors. Unlike inflammatory myopathies, these conditions do not involve the immune system attacking muscle tissue.

Classification

Acquired non-inflammatory myopathies can be classified based on their underlying causes:

Metabolic Myopathies

Metabolic myopathies are caused by defects in the biochemical pathways that provide energy to muscle cells. These include:

• Glycogen storage diseases: Conditions such as Pompe disease and McArdle disease result from enzyme deficiencies that affect glycogen metabolism.
• Mitochondrial myopathies: These are caused by defects in the mitochondria, the energy-producing structures within cells.

Toxic Myopathies

Toxic myopathies result from exposure to substances that damage muscle tissue. Common causes include:

• Alcoholic myopathy: Chronic alcohol consumption can lead to muscle weakness and atrophy.
• Drug-induced myopathy: Certain medications, such as statins and colchicine, can cause muscle damage.

Colchicine molecule

Endocrine Myopathies

Endocrine myopathies are associated with hormonal imbalances. Examples include:

• Hyperthyroid myopathy: Muscle weakness associated with an overactive thyroid gland.
• Hypothyroid myopathy: Muscle weakness due to an underactive thyroid gland.

Critical Illness Myopathy

This condition occurs in patients who are critically ill, often in intensive care units. It is characterized by muscle weakness and is associated with prolonged immobilization and the use of certain medications.

Symptoms

The primary symptom of acquired non-inflammatory myopathy is muscle weakness, which can vary in severity. Other symptoms may include:

• Muscle cramps
• Fatigue
• Difficulty with physical activities

Diagnosis

Diagnosis of acquired non-inflammatory myopathy involves a combination of clinical evaluation, laboratory tests, and imaging studies. Common diagnostic tools include:

• Electromyography (EMG): This test measures the electrical activity of muscles and can help differentiate between myopathic and neuropathic conditions.

Electromyography setup

• Muscle biopsy: A small sample of muscle tissue is examined under a microscope to identify structural abnormalities.
• Blood tests: These can detect elevated levels of muscle enzymes, such as creatine kinase, which indicate muscle damage.

Treatment

Treatment of acquired non-inflammatory myopathy depends on the underlying cause. General approaches include:

• Addressing the underlying cause: For example, discontinuing a medication that is causing muscle damage or treating a hormonal imbalance.
• Physical therapy: Helps maintain muscle strength and function.

Physical therapy session

• Nutritional support: Ensuring adequate nutrition to support muscle health.

Prognosis

The prognosis for individuals with acquired non-inflammatory myopathy varies depending on the specific condition and its severity. Some conditions may improve with treatment, while others may lead to progressive muscle weakness.

Related pages

• Myopathy
• Inflammatory myopathy
• Muscular dystrophy