A Muscle Disease is defined by some typical set of symptoms that are found across most types of muscular diseases. These include progressive weakness of the muscles, pain in the limbs, undue lethargy or exhaustion, cramping or stiffness of certain muscle groups, stiff joints and uncoordinated body movements. Many times, muscle diseases are also linked with delayed muscle motor skill development and progressive loss of muscle mass. The main types of muscle disease have been discussed below:
1. Neuromuscular Muscle Diseases
A neuromuscular disease is essentially a neurological problem that affects a single muscle or a group of muscles, limiting their range-of-motion and functional capability such as the ability to contract or relax. Among the more understood of neurological diseases is Muscular Dystrophy—this is an inherited disorder that impairs the functional capability and overall strength of muscles. Many kinds of Muscular Dystrophies have been established among which, those affecting the face, shoulders, neck and the pelvis are more prevalent. This includes:
- Duchenne Muscular Dystrophy—DMD
This dystrophy develops as a highly degenerative disease that causes gradual weakening of the voluntary muscles.. Here, the muscles are unable to create sufficient amounts of Dystrophin—a protein needed by the muscle cells for maintaining their normal, intact configuration. The onset period is between two and six years, i.e. early childhood. Symptoms include muscle wasting that is more visible in the hips, pelvis, shoulders and thighs.
- Becker Muscular Dystrophy—BMD
This muscular dystrophy too arises due to insufficient synthesis of dystrophin but its occurrence is a bit delayed, i.e. early late adolescence or early adulthood. The calves of the patient can be abnormally large but this dystrophy is less severe than DMD. However, there is a risk of the muscles of the heart too getting affected.
2. Metabolic Muscle Diseases
This refers to disease wherein the muscles are unable to complete some basic functions such as ensuring proper energy supply to the muscle fibers or the proper removal of toxins released during muscle exertion. Types of metabolic muscle diseases include:
- Phosphorylase Deficiency
This condition is also referred to as myophosphorylase deficiency or McArdle Disease. This muscle disease usually affects a small group of muscles. Here, the muscles are unable to metabolize carbohydrates properly. As a result, the muscles face a continued state of energy deficiency. This condition arises because of a genetic defect in the synthesis of myophosphorylase enzyme. In the absence of this enzyme, glycogen or glucose cannot be metabolized to supply the energy to hungry muscle groups. This muscle disease usually surfaces before the age of 15. Typical symptoms include recurrent cramping, intolerance to physical activity and muscular pain.
3. Inflammatory Muscle Diseases
These muscle diseases are characterized by increased inflammation of muscles or the tissues surrounding the muscles. Examples include:
- Dermatomyositis (DM)
This condition causes recurring inflammation of muscles since the immune system starts to interpret the blood vessels supplying the muscles as an external agent, i.e. this is an autoimmune problem. It can surface anytime between childhood and adulthood. The skin develops a typical purplish rash. The skin is scaly and rough with small, painful nodules of calcium present below the skin. Typical symptoms of DM include muscular weakness among the thighs, hips, upper arms, back and shoulders.
- Polymyositis (PM)
Polymyositis is a muscle disease that causes widespread inflammation of muscles and usually occurs after the age of 20 years. PM is more prevalent among females. It causes pronounced weakness among the shoulders, upper back and neck. Moving the neck becomes painful or the movement is uncoordinated. The neck and upper back tend to remain tender and this can be accompanied by respiratory problems and difficulty in swallowing.