What Causes Myopathy

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What Causes Myopathy ?

The main causes of myopathy can be genetic, inflammatory, endocrine or metabolic. At times, however, the cause may not be known, in which case it will be called an idiopathic disease. (See Reference 1) However, depending on the cause of the myopathy, it is categorized.

Genetic Cause of Myopathy
When the cause is genetic, the myopathy is referred to as inheritable myopathy. Muscular dystrophy, congenital myopathy and periodic paralysis are examples of inheritable myopathy.

A person has 23 pairs of chromosomes; of which one set is inherited from the mother and the other from the father. The inherited myopathy can either be linked to the autosomal genes or the X chromosome. Also, the defective gene can be recessive or dominant. In case the defective gene is dominant, just one copy of the gene is sufficient to cause the myopathy. However, if the defective gene is recessive, then the person would require 2 copies of the defective gene to get the disease. However, there is an exception when it comes to recessive X linked defective genes. For instance, muscular dystrophy is caused due to defective X chromosome linked gene and it is recessive in nature. For a girl to get muscular dystrophy, she must have 2 copies of the defective gene, and this rarely happens. On the other hand, as boys have a single X chromosome and hence, they can get muscular dystrophy if they inherit the defective gene. (See Reference 2)

Inflammatory Cause of Myopathy
This kind of myopathy is known as inflammatory myopathy and is a autoimmune disorder wherein the immune system of the body attacks healthy cells and tissues. In this case, the immune system attacks healthy muscles causing inflammation. The swelling damages the afflicted muscle. The severity of the disease varies from person to person, and so also the progress. Some examples of inflammatory myopathy include polymyositis (Develops in kids and women aged between 40 and 60 years), and dermatomyositis (Develops in kids aged between 5 years and 14 years). The latter can increase the chances of developing cancer of the skin. (See Reference 3)

Endocrine Causes of Myopathy
When an endocrine gland produces too much or too little hormone, it can result in myopathy, which can afflict kids as well as adults. Some examples of endocrine myopathy include steroid myopathy, hypothyroid myopathy and hyperthyroid myopathy. Cushing's disease and tumors that secrete hormones can also cause this kind of myopathy. (See Reference 3)

Metabolic Causes of Myopathy
In this kind of myopathy, there is absence of a particular chemical that is required for manufacturing energy in the cells of the muscles. This type of myopathy is associated with defective genes. In many metabolic myopathies, muscular weakness or exercise intolerance occurs when the person does some kind of physical activity. Some examples of metabolic myopathy include McArdle's disease caused due to deficiency of phosphorylase; and Tarui's disease caused due to deficiency of phosphofructokinase. There are several more. (See Reference 2)

More Articles :

What Causes Myopathy Reference
1. Encyclopedia of Children's Health: Myopathies

2. Neurology Channel: Inheritable Myopathy

3. Neurology Channel: Other Types of Myopathy