Causes of Myopathy
Myopathy is a muscle disease in which the muscle fibers do not function properly. It is divided into two categories, hereditary and acquired disorders. Myopathy can be caused by many different things. The disease can be brought on by: infection; muscle injury; disorder of electrolytes/vitamin deficiencies; or it also can be inherited. Not only are there different causes of myopathy but there are different types as well. Some of those types are: muscular dystrophies; congenital myopathies; metabolic; mitochondrial; inflammatory; endocrine; and toxic myopathies. In this paper, which aims to raise consciousness of this intriguing condition, we will explore the causes of different types of myopathy.
Inherited
One of the ways myopathy is acquired, is through being inherited. This is caused by a mutation or change in the genes. These genetic mutations cause defects in some of the proteins needed for muscle tone and contraction. Some mutations also interfere with ion channels, causing too much or too little current from flowing through the muscle cell. Myopathy can be inherited in several ways, such as x-linked, autosomal dominant, and autosomal recessive. X-linked means that the mutation is located on the X-chromosome. Autosomal is when the mutation occurs on a chromosome other than the X or Y, so it affects both male and female. The different types of myopathy linked to inheritance include myotubular, nemaline, and myotonia congenital just to name a few. “Nemaline myopathy was first described in 1963 and is characterized by the presence of rod-shaped structures (nemaline bodies) in muscle fibers. Patients with nemaline myopathy show several clinical features, including muscle weakness, respiratory failure, congenital malformation, and occasionally infant death. (Tsunoda 2017 et al)”. They are all linked to the mutation of the muscle cells or proteins. There are also inherited myopathies that are caused by or cause severe muscle injuries.
Muscle Injury
Muscle injuries are another cause of myopathy. These injuries can be triggered by a variety of phenomena. They range from very intense workouts, traumatic injury, and traumatic or non-traumatic rhabdomyolysis. Muscle injuries can also be classified as either traumatic (acute) or overuse (chronic) injuries. Acute injuries mostly occur in contact sports, such as football, basketball, or soccer because of the dynamic and high collision nature. Overuse injuries usually occur over a long period of time, resulting from repetitive micro-trauma to the muscle. There are several other types of muscle injuries such as muscle strains, cramps, contusions, and soreness. One type of myopathy caused by muscle injuries is called Duchenne Muscular Dystrophy. This disease causes symmetrical proximal gridle weakness, which is progressive loss of strength in the muscle. Another type of muscle injury is rhabdomyolysis. This happens when there is destruction of the skeletal muscle, causing leakage of the muscle protein (myoglobin) into the urine. Rhabdomyolysis can be caused by medication, alcohol, illegal drugs, extreme muscle strain, a very high body temperature, and or infection. This can also lead to kidney failure as well as death.
Infections
Infection is one of the most common causes of acquired myopathies. They range from viral infections (HIV; Influenza), Bacterial Pyomyositis (staphylococcus aureus), Spirochete (Lyme disease), and Parasitis infections such as trichinosis. HIV, being the more severe infection, is associated with a wide spectrum of neuromuscular and myopathic conditions. Myositis is also caused by infections like bacteria fungi. The bacteria invade muscle tissue directly, releasing a substance that damages muscle fibers.
Electrolyte Disorder/Vitamin Deficiency
Electrolytes are a substance that produce an electrically conducting solution when dissolved in water. They are vital to the normal functions of the human body. Also, they regulate our nerve and muscle function, our body’s hydration, blood pH, and the rebuilding of damaged tissues. When there’s an imbalance in electrolytes, one may experience weakness, bone disorder, blood pressure change or an irregular heartbeat. This imbalance can also cause kidney disease, or severe dehydration which leads to myopathy. Electrolyte imbalances coincide with vitamin deficiencies as well, due to a person having too much or not enough of a specific vitamin. Vitamin D deficiency is well known when it comes to causes of myopathy. It is the essential vitamin for strong bones, however, with the deficiency causing soft bones and skeletal deformities. Most people get much of their vitamin D from the sun. Some places have limited sunlight throughout certain times of the year and the people in those places are more prone to this deficiency.
Summary
We have explored the two main categories of myopathy, Inherited and Acquired. We have seen how it can be caused by and linked to a variety of conditions. Some of those causes include infections, muscle injury, inherited disease, and disorder of electrolyte levels/vitamin deficiencies. The aim of this paper was to bring about awareness of the subject. Reading it should give you a better understanding of the nature of Myopathy.
References:
Tsunoda, K., Yamashita, T., Motokura, E., Takahashi, Y., Sato, K., Takemoto, M., &… Abe, K. (2017). A patient with slowly progressive adult-onset nemaline myopathy and novel compound heterozygous mutations in the nebulin gene. Journal of The Neurological Sciences, 373254-257. doi: 10.1016/j.jns.2016.12.069
Fluss, J., Kern, I., de Coulon, G., Gonzalez, E., & Chehade, H. (2014). Vitamin D deficiency: A forgotten treatable cause of motor delay and proximal myopathy. Brain & Development, 36(1), 84-87. doi: 10.1016/j.braindev.2012.11.014
