Between 600 and 800 different diseases belong to the large group of neuromuscular diseases that are associated with muscle atrophy, can lead to slight limping, but also to respiratory failure, and for which there is as yet no cure. Learn more about different types of muscle atrophy, typical symptoms of muscle atrophy, and treatment of the disease here.
What is muscle wasting?
In muscle atrophy, due to mostly hereditary causes, the muscles of the trunk, arms and legs, but also the face, and inside the body such as the swallowing muscles, the heart muscles or the eye muscles, regress. Muscle wasting diseases are a group of 600 to 800 very different diseases, depending on the classification, in which a genetic defect either leads to the death of the muscle cells (myogenic muscle wasting), in which the nerve cells supplying the muscles die (neurogenic muscle wasting), or in which the transmission of nerve impulse to muscle is disturbed, e.g., by autoantibodies, as in myasthenia (myasthenia gravis). While diseases of the first group are usually called myodystrophies or myopathies, those of the second group (spinal) are called muscle atropies. Together, they are called neuromuscular diseases.
Muscle atrophy: forms and naming
Muscle atrophy diseases are named either after their discoverer (Werdnig-Hoffmann, Kugelberg-Welander, Duchenne, Becker-Kiener) or after the body region in which they occur: For example, the facio-scapulo-humeral type mainly affects the face, scapula and upper arm, while the oculo-pharyngeal type affects the eyes and swallowing muscles. Depending on the form, the disease may appear in the unborn child or in the first months of life, while other forms develop later in life. The earlier the disease appears, the more aggressive its course usually is. While early forms often lead to death in the first two decades of life, later onset of the disease usually results in only a few deficits due to muscle atrophy and life expectancy is not limited. Exceptions are, on the one hand, the non-hereditary muscle wasting disease amyotrophic lateral sclerosis, which usually only occurs at an advanced age, shows a rapid deterioration of symptoms and leads to death after a few years, and, on the other hand, myasthenia gravis, in which the body produces autoantibodies against the transmitter synapses on the muscle cells. In addition to rapid muscle fatigue, which usually manifests as double vision, a thymic tumor is often found.
Therapy and treatment for muscle atrophy
Therapeutically, those affected can often be helped with thymus removal and medications that suppress the immune system. Particularly problematic about muscle atrophy is the death of the muscles that support breathing as auxiliary respiratory muscles. The more severely these muscles are affected, the more difficult it is to breathe deeply – in the long term, too little oxygen reaches the body. In addition, the disease can also affect the swallowing and heart muscles – swallowing disorders and pronounced cardiac insufficiency can be the consequences. These diseases are distinguished from normal muscle atrophy, which occurs after prolonged immobilization of a body part, e.g. a broken arm in a plaster splint, or after confinement to bed during a prolonged illness. In this case, however, no muscle cells perish, but the individual muscle cells simply shrink with the decrease in the demands placed on them, only to increase in size again after the illness and renewed exertion.
Symptoms: What are the manifestations of muscle atrophy?
What all muscle wasting diseases have in common is that movements for which the affected muscles are needed can no longer be performed fluidly at first, and later only incompletely or not at all. So if the leg muscles are affected, the first signs of muscle wasting disease may be stumbling more often, losing strength more quickly, and fatiguing the legs more quickly. If the disease begins in the first months of life, even learning to walk may be impossible. If the disease begins in infancy, already learned skills such as climbing stairs are lost again, and standing up from a squatting position is at some point only possible if the affected person pulls himself up (i.e. supports himself with his arms to achieve a vertical position).
Muscle atrophy in children
Children with muscle wasting exhibit a characteristic waddling gait and often have stout calves, which is not due to increased musculature but rather to storage of fatty tissue. In the more severe forms of muscle atrophy, limited mobility inevitably leads to a curved posture and contractures of the muscles, so that walking eventually becomes impossible. Sitting in a wheelchair and the curved posture promotes the progression of the disease in that the posture can no longer support the respiratory muscles and breathing through becomes increasingly difficult. Poor ventilation of the lungs leads to increased respiratory infections and limited lung capacity. Chronic lung infections and increased respiratory insufficiency are ultimately the main reason for decreased life expectancy.
