Myopathy: What is it, why does it develop and how does muscle disease manifest?

Myopathy is a neuromuscular disease . These diseases affect the nerve and muscle areas. However, myopathy mainly affects the skeletal muscles, especially the muscles of the girdle. Myopathies include a number of diseases, which vary in cause and symptoms.

Nerve-muscle diseases affect:

• peripheral nerves such as neuropathy or polyneuropathy
• nerve - muscle connection
• muscles , and therefore myopathy

In myopathy, muscle involvement occurs  , in most cases symmetrically. The skeletal, proximal (close to the head and torso) transverse striated muscles are affected. The disease can be congenital , hereditary or acquired , or even primary  and  secondary .

As primary myopathies, they are genetically and autoimmune conditioned . Secondary arises from other diseases , such as complications of internal, metabolic or cancerous diseases, but they can be caused by toxic effects or drugs.

Neuromuscular diseases are included among the rare diseases. Rare diseases are those that affect less than 5 in 10,000 people.
Or one person for 2000 or more people.

Myopathy affects the muscle , damaging it, in some cases the muscle fiber is replaced by connective or adipose tissue. This change, remodeling, of the tissue will cause a malfunction . However, myopathy does not have a sensitivity disorder , as is the case with neuropathies.

The table shows congenital and acquired myopathies

Thus, myopathy is a muscle disease that can be congenital, also referred to as hereditary myopathy. But myopathy can occur even during life. And this type is called acquired myopathy.

Among the hereditary myopathies include, for example, muscular dystrophy, as well as Duchenne muscular dystrophy. Another example is autoimmune myopathy, or myositis (polymyositis or dermatomyositis).

Another example is acquired myopathies. Acquired myopathies arise as a result of another disease. We mention, for example, myopathy in thyrotoxicosis or as a result of taking medication. Drug myopathy is, for example, statin myopathy. Another species is, for example, myotonia.

Myopathies include:

• congenital myopathy, which is damage to the structure of muscles
• progressive muscular dystrophy
• myotonia
• myotonic dystrophy
• familial periodic paralysis
• endocrine myopathy
• metabolic as well as mitochondrial myopathy
• inflammatory myopathy
• drug, including statin myopathy
• toxic myopathy

As can be seen from the above, myopathies cover various forms of the disease. They have different causes as well as different symptoms. For example, inflammatory myopathies, i.e. myositis can have an infectious origin. But there may also be an autoimmune process behind them.

Infectious myopathy can be caused by a virus (coxsaskie, influenza), as well as bacteria (boreliosis, TB), a parasite (toxoplasmosis) or mycosis. The cause of autoimmune diseases is a non-infectious inflammatory process, which is the result of excessive activity of the body, while also damaging teluvate cells and tissues.

Thyrotoxicosis or diabetes mellitus are also known diseases. Metabolic myopathy can develop in these as well as in other diseases. Of course, no matter what the cause, a thorough examination of the difficulties is needed, such as a symmetrical decrease in muscle strength in particular.

What are the symptoms of thyroid disease and what is diabetes .

As mentioned, myopathy is a neuromuscular disease. And these diseases have common symptoms that may or may not occur. The basic symptoms of neuromuscular diseases include:

• muscle weakness
• pain muscles
• impaired exercise
• rapid muscle fatigue, especially excessive, excessive fatigue
• muscle cramps
• muscle twitches, technically referred to as fasciculations
• muscle stiffness and impaired muscle relaxation after contraction
• muscle atrophy
• muscle shortening, ie contractures
• in neurodegenerative disease it is also a disorder of sensitivity

Muscle diseases, ie myopathies, manifest themselves depending on the type of disease. Myopathies are a diverse group that covers a variety of diseases. However, one of the typical symptoms of muscle disease is muscle weakness.

Myopathy affects the skeletal transverse striated muscles. Muscle weakness is in most cases symmetrical and mainly affects the muscles of the upper girdle. However, in some cases also the lower muscles. As with the distal form. 

Manifestations of myopathy are also referred to as myopathic trias listed in the table

Among the symptoms that can occur with myopathy include:

• muscle weakness
• hypotrophy to muscle atrophy (weakening)
• pseudohypertrophy of the calves, enlargement of the calf muscles
• shortening of Achilles tendons
• deterioration of muscle reflexes, but preserved sensitivity
• cardiomyopathy
• respiratory failure, ie respiratory distress
• skeletal deformation

Thus, the main problem with myopathy is muscle weakness. Muscle weakness should be observed, for example, during impaired gait. Walking up the stairs is also a big problem, but also getting up from a squat or sitting. Muscle strength and performance decrease. Decreased muscle strength is manifested by faster muscle fatigue and decreased muscle performance. Overall, the tolerance of physical activity of the muscles decreases.

Muscle involvement is usually bilateral, so it is symmetrical. In a few cases, an asymmetry of difficulty is present. The disability mainly affects the muscles of the lower limbs, and therefore their girdles. 

The girdle of the upper limb is the area of ​​the shoulder, collarbone and scapula.
The braid of the lower limb is in the place of the pelvis and seat.

Falls are common due to difficulty walking and getting up from the ground. Running is also problematic. Sometimes there are also disorders of movement coordination, muscle cramps or twitching. If the disease affects the muscles of the girdle of the upper limbs, the person in question also has difficulty with operations such as combing or hanging clothes. 

In addition, speech problems, swallowing, and a problem with lifting the head may occur. One has difficulty breathing. Atypical symptoms include fever, muscle wasting, and muscle pain that do not occur in every patient.

In myotonic myopathy, there is a burying of the toe and a problem with vocal expression. Many times people with myopathy are often poor, have irregular heartbeat and joint movement disorders.

Myopathy is not a neurodegenerative disease, so the disease does not affect the nerves. This means that sensitivity is not affected. Muscle reflexes may be weakened, but they are not completely disturbed. Muscle pain may or may not be present. 

In the diagnosis of myopathies, it is important to detect the manifestations of the disease, ie the clinical picture and anamnesis. As muscle weakness is also present in other diseases. A good example is weakness and muscle pain in fever or flu.

What is the flu and what is a fever?

Subsequently, other examinations are performed, as well as EMG, which is an electromyograph. Laboratory examination, where the blood is biochemically examined for muscle enzymes (CK, myoglobin, AST, ALT, LD). Other methods include, for example, muscle tissue collection, or muscle biopsy. DNA analysis can also be important.

Imaging methods such as  CT and  MRI are added, as well as respiratory examinations. Respiratory function is assessed by spirometry. Cardiac examination, and therefore ECG, ECHO, is also important.

As well as the symptoms of the disease, the course depends on the type of myopathy. In general, it can be assessed that in the case of congenital diseases, the first manifestations occur in childhood. As is the case with various muscular dystrophies.

For example, there is slow motor development. The full manifestations of the disease occur around the 3rd - 5th year of life. With Duchenne form of muscular dystrophy, independent walking is lost between the ages of 10 and 13.

In congenital diseases, the disease may be progressive and develop over time. If left untreated, it is also a fatal disease. However, many forms of myopathy, due to their nature and origin, are still completely incurable.

The acquired forms of the disease manifest themselves later. As is the case, for example, with inflammatory myopathies, but also if it is the result of another systemic disease. For example, in myositis, the adult population is affected between the ages of 30 and 60.

If the cause is an endocrine disease, as in the case of thyrotoxicosis, then muscle weakness or loss of muscle mass depends on the degree of the underlying disease. If myopathy develops after an injury, it usually has an immediate effect.