What to Expect After a Myopathy Diagnosis

Causes, Symptoms, Treatment and Prognosis of Myopathy

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Myopathy is a term used to describe diseases of the muscle. If you have been diagnosed with myopathy, or if you are currently being evaluated for possible myopathy, there is a strong chance that you have not heard about myopathy until now, because it is not as common as other medical conditions. You may have questions about the diagnostic process, what you should anticipate in terms of prognosis and treatment, and whether other members of your family might also be at risk of myopathy.

What Is Myopathy?

Myopathy refers to a disease of the muscles. When a person has a disease of the muscles, the muscles work less effectively than they should. That can occur when the muscles do not develop properly, when they have become damaged, or when they are lacking important components.

Muscles normally work by contracting, which means becoming shorter. A normal muscle is composed of proteins and other structural components that move in a coordinated manner to contract the muscle. When any of these components is defective, this may cause myopathy.

There are a number of different causes of muscle disease, and consequently there are a number of different myopathies. Each of the different myopathies has its own specific name, cause, set of diagnostic tests, anticipated prognosis, and treatment. Some myopathies are expected to worsen over time, while some are fairly stable. Several myopathies are hereditary, and many are not.

Symptoms of Myopathy

In general, myopathy causes muscle weakness. The most common pattern of weakness is described as proximal weakness. This means that the muscles of the upper arms and upper legs are more obviously weakened than the muscles of the hands or feet. Sometimes, myopathy weakens the respiratory muscles (muscles that control breathing).

Other characteristics of myopathy include fatigue, lack of energy, and worsening weakness as the day goes on or progressive weakness with exertion.

Often, when people have had myopathy for years, muscle atrophy begins to develop, which is the thinning out and wasting away of muscles, weakening the power of the muscles even more. Myopathy is often associated with abnormal shape of the bones, often because the muscle weakness prevents the bones from maintaining their normal shape.

How Will I Know If I Have Myopathy?

In general, myopathy is a difficult diagnosis. If you have symptoms of myopathy, there is a strong chance that you will get a referral to a neurologist or a rheumatologist, or both, depending on which of your symptoms is most prominent.

Diagnostic testing includes a careful physical evaluation, including examination of your skin, your reflexes, your muscle strength, your balance and your sensation. Your doctor will take a detailed medical history and ask you about your family medical history.

There are also a number of tests that you may need, depending on your medical history and the findings on your physical examination. These tests include blood tests, such as a complete blood count (CBC) and electrolyte levels.

Other blood tests include erythrocyte sedimentation rate (ESR) and antinuclear antibody test (ANA), which measure inflammation. Creatine kinase in the blood can evaluate muscle breakdown. Thyroid tests, metabolic and endocrine tests may be needed.

Another test called an electromyography (EMG) is an electrical test that assesses muscle function through the use of needles that detect several characteristics of your muscle structure and movement. Sometimes, highly specialized tests such as muscle biopsy and genetic testing can help diagnose certain types of myopathy.

Types of Myopathy

Congenital myopathy means myopathy that a person is born with.

Many of these conditions are believed to be hereditary, or passed on through families by genetics. And, while the symptoms of congenital myopathies often begin at a very young age, that is not always the case. Sometimes a hereditary medical illness does not begin to produce symptoms until a person is a teenager or even an adult.

Common inherited myopathies include:

  • Mitochondrial myopathy: This is a disease caused by a defect in the energy producing part of the cell, called the mitochondria. There are several types of mitochondrial myopathy, and while they can be caused by hereditary mutations (abnormalities in the genes) they can also occur without any family history at all.
  • Metabolic myopathy: This is a group of diseases caused by metabolic problems that interfere with the function of a muscle. There are a number of different hereditary metabolic myopathies caused by defects in the genes that code for certain enzymes that are necessary for normal muscle movement.
  • Nemaline myopathy: This is a group of disorders characterized by the presence of structures called ‘nemaline rods’ in the muscles. Nemaline myopathy is often associated with respiratory muscle weakness.

Congenital myopathies include:

  • Central core myopathy: This is a hereditary myopathy that causes weakness, bone problems, and severe reactions to some medications. The severity of this disease varies, causing profound weakness among some people and only mild weakness in others.
  • Muscular dystrophy: This is a group of diseases caused by degeneration of the muscles or abnormally formed muscle cells. Technically, muscular dystrophy is not myopathy, but there is often overlap in the symptoms, and therefore you may initially get a medical evaluation that is aimed at determining whether you have myopathy or muscular dystrophy. The main difference between myopathy and muscular dystrophy is that muscles do not function properly in myopathy, whereas the muscles degenerate in muscular dystrophy.

Myopathy can also be caused by a variety of illnesses that produce a range of physical problems in addition to issues with muscle contraction.

Common acquired myopathies include:

  • Inflammatory/ autoimmune myopathy: This occurs when the body attacks itself, causing degeneration of the muscles or interfering with muscle function. There are a group of myopathies characterized by inflammation in or near the muscle. Some of these conditions include polymyositis, dermatomyositis, sarcoidosis, lupus, and rheumatoid arthritis.
  • Toxic myopathy: This occurs when a toxin, a medication, or a drug impairs muscle structure or function.
  • Endocrine myopathy: This occurs when a disorder of the hormones interferes with muscle function. The most common causes include thyroid or adrenal gland problems.
  • Infectious myopathy: This may happen when an infection prevents the muscles from functioning properly.
  • Myopathy secondary to electrolyte imbalance: Electrolyte problems, such as excessively high or low potassium levels, can interfere with the function of the muscles.

What Should I Expect If I Have Myopathy or Possible Myopathy?

In general, congenital myopathy is expected to worsen or stabilize over time, and is not typically expected to improve. The myopathies that are not congenital, such as infectious, metabolic, or toxic myopathies, may improve once the cause of the myopathy is well controlled.

Getting a good grasp of your specific condition is important to making sure you have the best outcome possible. If you have a type of myopathy that is not expected to improve, you should pay close attention to issues such as atrophy, pressure sores, and making sure that you maintain optimal participation in physical therapy so that you can function at your best.

Treatment 

There are not effective treatments that can regenerate or heal your muscles to cure myopathy. When there is an identifiable cause, such as an endocrine problem, correcting the cause can help improve the symptoms of myopathy, or may at least help prevent it from worsening.

Often, respiratory support is the key component in advanced myopathy, so that your breathing can be safely maintained.

Will My Family Get Myopathy If I Have Myopathy?

Yes, some myopathies are indeed hereditary. If you have a hereditary myopathy, then there is a chance that some of your siblings, your children, nieces and nephews, or other relatives could also develop myopathy. It is important to let your family know about your condition, as an early diagnoses can help them get earlier treatment and supportive care.

Some of the myopathies that are not specifically considered congenital or hereditary may still have a tendency to run in families, so your family might be at increased risk even if you have a myopathy that is not known to be hereditary.

A Word From Verywell

Myopathy is not a very common condition. Muscle disease can certainly impair your quality of life. However, many individuals who are diagnosed with myopathy are able to maintain productive lives, including maintaining satisfying employment and enjoying a happy family and social life.

Sources:

Lundberg IE, Miller FW, Tjärnlund A, Bottai M, J, Diagnosis and classification of idiopathic inflammatory myopathies, Intern Med. 2016 Jul;280(1):39-51

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