What are Myopathies?
Muscles generate the force required for movements. Myopathies refers to the various conditions or disorders that affect the skeletal muscle, it’s cell structure and metabolism, which cause malfunction of the muscle.
Myopathies Symptoms and Signs.
There are different types/forms of myopathies, and each type manifests with unique features. In general, however, most people with myopathies show one or more of the following symptoms and signs:
- Progressive weakness in the proximal muscles of the limbs which causes waddling gait, difficulty rising from sitting, and difficulty raising the arm above the head.
- Muscle pain (myalgias)
- Progressive fatigue
- Decreased exercise tolerance
Myopathies Common Causes
Myopathies occurs after something disrupts and interferes with the normal structure and/or the normal metabolic processes of the muscle cells, resulting in the muscle malfunction. The underlying causes for myopathies can be genetic abnormalities, some drugs, inflammation, infections, hormonal deficiencies or excess, vitamin deficiencies and electrolyte disorders.
There are two main categories of causes of myopathies, which include inherited or acquired categories:
Inherited myopathies include some conditions like:
- Duchenne muscular dystrophy
- Becker muscular dystrophy
- Type 1 and 2 myotonic dystrophies
- Facioscapulohumeral dystrophy
- Central core myopathy
- Pompe’s disease
Acquired myopathies include some conditions like:
- Inclusion body myositis
- Viral infections (HIV, influenza virus, Epstein-Barr virus)
- Lyme disease
- Systemic lupus
- Some medications like steroids, statins, fibrates, amiodarone, among others
- Vitamin D deficiency.
Diagnosing the cause of myopathy requires eliciting a complete medical history which should explore, among other things, the use of certain medications, presence of certain infections or other diseases that might help to clarify the diagnosis. Other important aspects of the history family history as well as childhood developmental milestones. Physical examination is done to determine the pattern of muscle weakness and to look for other useful signs to guide diagnosis. In addition, your doctor will usually recommend some tests to confirm the diagnosis, including:
- Blood tests. In order to measure some products in your blood that might indicate the presence of muscle damage, including elevations in creatine phosphokinase (CPK), aldolase, lactate dehydrogenase (LDH) and lactate. Blood levels of pertinent vitamins and hormones may also be measured.
- Nerve conduction study. This is often carried out before needle EMG in order to exclude neuropathies which may present similarly to muscle disorders.
- Electromyography (EMG).In which your doctor will insert a needle electrode through your skin into selected muscles to evaluate their electrical activity. This often confirms the presence of muscle disorder and helps differentiate it form neuropathy. It may also give specific clues to final diagnosis in some cases, such as myotonic dystrophy.
- Muscle biopsy. Tissue examination might help determine the specific type of muscle condition, especially in those with certain genetic muscle disorders.
Treating myopathies depends on the underlying cause of this condition and whether it’s an inherited or acquired myopathy.
Most cases of inherited myopathies have no cure and the treatment is mostly supportive during the years of life, including some options like physical therapy, nutrition, and genetic counseling. There are some hereditary myopathies like Duchenne muscular dystrophy, that after been treated with corticosteroids, has shown some improvement within the strength and also have slow the progression of the disease. Some rare disorders such as Pompe disease now have available treatments that can halt the progress of disease and prolong life lived without disability.
The best treatment option for acquired myopathies is to identify and correct the underlying cause. This includes treating responsible infections, withdrawing culpable medications, and improving general conditions. Immune modulators may be employed in cases of inflammatory myopathies such as polymyositis. Physical therapy may also be necessary in order to prevent contractures and disabilities.
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