Which are the symptoms?
The main symptom generally is weakness (hyposthenia) of the large proximal muscles, in the upper and/or lower limbs. Sometimes, especially in inflammatory and dysmetabolic forms, muscular pain (called myalgia) and/or cramp-like syndrome may be associated. Hyposthenia is associated with a progressive muscular hypotrophy of the same muscles. Muscular hypertrophy (or pseudohypertrophy in some dystrophies) can occur in rare cases. Another frequently present symptom is fatigability, when the patient is able to perform an exercise but gets tired quickly. Finally, abnormalities of muscle contraction may be observed, such as myotonia (difficulty releasing a muscle after contraction) and involuntary muscle movements. It should not be forgotten that sometimes myopathies are associated with systemic symptoms that can affect various organs, especially the heart and lungs, and, in rarer cases, the dermis, brain, and eyes.
- muscle weakness
- muscle atrophy (rarely hypertrophy)
- myalgia and/or cramps
- abnormalities of muscle contraction
- possible systemic symptoms
How is it diagnosed?
A correct diagnosis requires a thorough neurological examination, determining certain dosage of muscle enzymes in blood and inflammatory, metabolic and hormonal indices, as well as electromyographic examination. If indicated, muscle MRI may be helpful. Muscle biopsy and a series of genetic tests allow in most cases to complete the diagnostic process by identifying the cause of the disease.
How is it treated?
The treatment of myopathies depends on their cause. If the cause is acquired, as in inflammatory forms, anti-inflammatory drugs (such as cortisone), immunomodulatory drugs (such as intravenous immunoglobulins) or immune-suppressive and biological drugs (monoclonal antibodies) can be used. If the cause is an endocrine disorder, such as dystothyroidism, this dysfunction needs simply to be corrected. For metabolic forms, there are some drugs that improve mitochondrial function, while for glycogenosis, enzyme replacement therapy is available for type 2 form. In channelopathies, there are certain drugs that stabilize the muscle membrane while improving symptoms. In myotonic forms, there are symptomatic drugs that reduce the disorder. For muscular dystrophies, drugs that can be used in the forms known as Duchenne dystrophy have become available only recently. Many of these drugs are still in experimental trials, and may be used within clinical trials (oligonucleotides, monoclonal antibodies, gene therapy), and in the coming years their use may be expanded to various forms of muscular dystrophy.