Myopathy is the medical term for muscle diseases. "Myo" stands for muscle and "pathie" for disease. The skeletal muscles are most frequently affected, less frequently the heart (medically cardiomyopathy). Myopathy is an umbrella term for all diseases that affect the muscles.
As there are many different causes of muscle diseases and muscles make up a large proportion of the mass of the human body, the various causes and characteristics of muscle diseases are discussed in more detail below.
There are a large number of different muscle diseases, which can be roughly divided into
- congenital (congenital) and
- acquired forms.
The congenital forms are inherited, i.e. they are already present at birth (or in the womb). This is why they are also referred to as primary forms (primary = first). They often cause problems at birth, but sometimes only become noticeable after a delay. Males are much more frequently affected by inherited muscle diseases, which is due to inheritance. Boys have one Y and one X chromosome, girls have two X chromosomes. As a healthy X chromosome protects against the disease, both genes (the one from the mother and the one from the father) must be defective in girls and only one in boys.
Acquired myopathies only develop in the course of life due to external influences (e.g. taking special medication) or other diseases (including rheumatic diseases). They are therefore also called secondary myopathies (secondary = second, subsequent). Rheumatism is often associated with joint pain and is also referred to as "joint rheumatism". However, it can also affect the muscles.
What exactly happens to the muscles in myopathy?
Myopathy is a disorder of muscle function or muscle structure.
These functional disorders can be roughly divided into
- Reduction in muscle mass (muscular dystrophy)
- Disorder of muscle flaccidity (myotonic syndromes)
- Restriction of energy supply (mitochondrial myopathy)
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Which form of myopathy is the most common?
The most common form of myopathy is muscular dystrophy (muscle wasting). This typically results in a reduction in muscle mass, which can be attributed to various causes. Here too, a distinction is made between
- primary and
- secondary muscular dystrophies.
Primary means that the cause lies in the muscle itself. These are usually hereditary diseases, which are very rare.
Secondary forms of muscular dystrophies are caused by other diseases or pathological conditions, not by the muscle. They are not to be classified as an independent disease, but rather as a symptom of another underlying disease.
The causes of secondary myopathies include
Myopathy can also be caused exogenously by
- Toxins
- alcohol
- Medication such as statins or cortisone
Are there several types of primary muscular dystrophy?
Depending on the inheritance and the muscles affected, congenital muscular dystrophies can differ greatly in their appearance and symptoms. They are often named after the names of the people who first described them, but they are all equally characterized by a progressive breakdown of muscles.
The most common forms of primary muscular dystrophies are Duchenne myopathyand Becker Kiener muscular dystrophy. Limb girdle dystrophies and Emery-Dreifuss muscular dystrophy type 1 also belong to the group of muscular dystrophies.
What causes secondary muscular dystrophies?
In secondary muscular dystrophies, the muscles themselves are healthy, but the loss of muscle mass is caused by other diseases. For example, malnutrition with protein deficiency, tumor diseases or vitamin deficiency can lead to a loss of muscle mass.
However, immobility, i.e. restriction or loss of mobility, also often leads to a loss of muscle mass due to a lack of exercise. Examples of this are severe bone and joint injuries that do not allow you to get out of bed. Furthermore, a slipped disc can also lead to paralysis of the muscles and a reduction in muscle mass.
Artificial coma is a rare but also possible cause of secondary muscle atrophy. The longer this lasts, the greater the muscle atrophy and the longer it takes to rebuild the muscles afterwards.
What is myotonic myopathy?
Myotonic muscle diseases are characterized by prolonged muscle tension. As a result, the muscle cannot relax properly, which leads to cramping. To explain the term: "tonus" is the technical term for tension, "myo" stands for muscle. This form of muscle disease, which tends to cause cramps, is therefore also known as myotonic myopathy.
However, as it is not only the muscles that cause problems, but also many other organs and organ systems (e.g. the eyes, heart, brain and psyche) are affected, it is referred to as "myotonic syndromes". In medicine, complex diseases with many different manifestations and symptoms are often referred to as syndromes.
In most cases, myotonic syndromes are congenital muscle diseases, but there are also acquired myotonia, for example as a result of nerve diseases, medication and its side effects, drug and alcohol abuse or kidney disease.
What is characteristic of mitochondrial myopathies?
Mitochondrial myopathies are characterized by a disturbance in the energy metabolism of certain cell components, the so-called mitochondria. The mitochondria are the power plants of the cells, where the entire energy metabolism takes place. As the skeletal muscles make up the largest proportion of the body's musculature and this is where most of the movement and use of force takes place, symptoms of mitochondrial myopathies also affect the skeletal muscles almost without exception.
However, muscles of other organs and organ systems can also be affected, which is why many different symptoms and problems can occur here too. For example, the nervous system, the eye and the inner ear can also be affected. However, disorders of the gastrointestinal tract, liver or pancreas also occur. Mitochondrial diseases are often referred to as multisystem diseases, as many different organs are affected.
The main symptom of myopathy is muscle weakness. How severe this is depends primarily on the cause of the myopathy. Mild myopathies, for example, are only manifested by weakness during or after exercise. A restriction is therefore rarely observed in everyday life, at most during sporting exertion or heavy physical work.
However, there are also severe myopathies such as Duchenne muscular dystrophy. This muscle weakness is initially only noticeable through frequent stumbling or falling. From the age of 5 to 7, affected children can only stand up from a sitting position with help. From the age of 12, most patients with Duchenne muscular dystrophy are dependent on a wheelchair; from the age of majority, patients generally require full-time care.
If myopathy is suspected, a detailed family history should be taken first. Mothers in particular can be unrecognized, i.e. healthy, carriers of the defective gene due to the inheritance described above.
Laboratory diagnostics provide further indications of possible causes. Blood, for example, provides information about nutrient deficiencies or can be used for genetic testing.
Before a genetic analysis is carried out, an electromyography (EMG) is usually performed first. This is a neurological diagnostic procedure that measures electrical muscle activity. In this way, muscle weakness can be detected. EMG can also be used to differentiate whether the cause of the muscle weakness lies in the muscles themselves or in the nerve tissue.
Imaging procedures such as computer tomography or magnetic resonance imaging show particularly affected muscle areas and can illustrate abnormalities.
A muscle biopsy, in which the doctor takes a tissue sample from the muscle and then sends it to the laboratory for histological examination, serves to further and accurately confirm the diagnosis. However, it is only carried out if there is sufficient suspicion of a primary myopathy, as it is a sometimes painful diagnostic procedure with a risk of complications (bleeding, secondary bleeding, muscle and nerve injury).
The treatment methods for myopathy are varied and depend on the cause. In secondary myopathies, the underlying disease is treated first, which in the majority of cases also alleviates the muscle weakness. For example, patients with hypothyroidism are given thyroid hormones, while vitamin or mineral deficiencies can be alleviated by supplementing the corresponding vital substance.
However, causal treatment is not possible for primary myopathies. The aim of therapeutic measures is to minimize the consequences of muscle weakness for as long as possible.
Physiotherapy and drug therapies can alleviate the symptoms and help to maintain muscle strength, while occupational therapy helps patients to cope with everyday life. Those affected also benefit from appropriate aids such as a walking stick, a rollator or a wheelchair.
If not only the skeletal muscles but also the heart muscles are affected by the muscle weakness, drug therapy can be helpful. Patients are then given drugs to strengthen the heart muscles and combat cardiac arrhythmia. It may also be necessary to implant a pacemaker for therapy.
Myopathies are therefore a group of muscle diseases with a wide variety of causes. The symptoms and treatment of muscle diseases are just as varied as the causes.
