Myopathy Types

Myopathy is a general term that describes a class of neuromuscular disorders. All conditions characterized as a type of myopathy cause muscle pain, weakness and stiffness. Apart from these commonalities, various types of myopathy have unique causes, symptoms and treatments.

For example, while some myopathy patients are born with congenital myopathy, others will develop different types of myopathy later in life.

The following outlines the four basic categories into which all types of myopathy are classified:

  • endocrine-related myopathies marked by gland malfunction and imbalanced hormones
  • genetic myopathies characterized by genetic defects that cause people to be born with this condition
  • inflammatory myopathies marked by chronic muscle and/or skin swelling
  • muscular dystrophies characterized by muscular deterioration during childhood or adolescence.

In this section, we will take a closer look at each of the different types of myopathy. Our articles will outline the causes, symptoms and treatments for each type of myopathy.

Dystrophies

Although muscular dystrophies (MDs) are actually different from myopathy itself, the way in which they damage and weaken the muscles has led many medical experts to classify them as a type of myopathy. In general, dystrophy disorders refer to a group of more rare myopathies that typically develop in children and adolescents. As such, they usually result from some underlying genetic defect the patient has.

Aside from these commonalities, MD can vary from patient to patient in the area of the body it affects, as well as in the severity of symptoms. Some of the more common types of muscular dystrophy include Duchenne MD, Becker’s and limb-girdle MD. About one in every 10,000 boys suffers from Duchenne muscular dystrophy.

Congenital Myopathies

Also referred to as genetic myopathies, congenital myopathies describe the types of conditions in which genetically inherited defects cause muscle deterioration, pain and general weakness. In general, the genetic abnormality that causes congenital myopathy is a dominant characteristic. This means that, for a child to be born with this disorder, only one of his parent’s has to pass along the defect.

Because the gene that causes congenital myopathy lies on the X chromosome, baby girls and boys are equally likely to develop this condition.

Unlike other types of myopathy that people develop later in life, there is no cure for congenital myopathy. Medications and physical therapy are the typical treatments for congenital myopathy.

Inflammatory Myopathies

Non-congenital types of myopathy characterized by recurring muscle swelling and weakness are known as inflammatory myopathies. Pain, muscle tenderness and skin redness are also common symptoms associated with this type of myopathy.

Within this category are a number of myopathies, the most common of which are dermatomyositis and polymyositis. While dermatomyositis affects a person’s connective tissues (i.e. tendons, blood vessels and cartilage), polymyositis primarily affects a person’s muscles.

Depending on the precise type of inflammatory myopathy, patients can be so seriously affected that they are unable to walk. In some cases, certain types of cancer are related to inflammatory myopathies.

Myotonic Myopathies

Also known as Thomsen’s disease, myotonic myopathies are rare, genetically inherited types of myopathy marked by the inability to loosen muscles once they contract. Infants born with myotonic myopathy will start to display symptoms by stiffening their hands and legs. If doctors suspect that a newborn has myotonic myopathy, they will perform an electromyogram, a diagnostic test that measures the muscles’ electrical impulses.

If myotonic myopathy develops later in life, it is known as Steinert’s disease. Depending on the cause, symptoms of developed myotonic myopathy can vary widely.

Resources

Health A to Z (updated August 14, 2006). Myopathies. Retrieved January 3, 2008, from the Health A to Z Web site: http://www.healthatoz.com/healthatoz/Atoz/common/standard/transform.jsprequestURI=/healthatoz/Atoz/ency/myopathies.jsp.