Any medical condition that causes muscle inflammation to occur in one or several muscles is commonly referred to as myositis. When a person suffers from this condition they will generally experience a great deal of swelling, muscle weakness, and pain. Some of the most common causes of myositis include injury, side effects from certain medications that are taken, infection, and autoimmune conditions.
In each individual situation, the specific cause of the occurrence of myositis is used to determine the category it falls in.
Myositis caused by inflammatory conditions
There are certain types of medical conditions that can lead to inflammation in the body and ultimately affecting a person’s muscles. In a majority of situations it is due to autoimmune conditions where damage occurs because of damaging antibodies that the body produces, and then attacks its own tissues. Some common inflammatory conditions that can result in myositis that can be severe include the following:
- Inclusion body myositis
- Polymyositis
- Dermatomyositis
Myositis in milder forms is often caused by the following inflammatory conditions:
- Rheumatoid arthritis
- Scleroderma
- Lupus
There is often a prolonged level of treatment required for myositis caused by inflammatory conditions, as they tend to be the most serious.
Myositis that occurs because of infection
The most common type of infection that causes myositis is viral infections. On rare occasions it can also be caused by fungi, bacteria, and various other organisms. Tissue of muscle can be invaded by bacteria or viruses either directly or indirectly through the muscle fiber damaging substances that are released. Myositis can also be caused by the common cold, the flu virus, and human immunodeficiency (HIV).
Myositis caused by medications
Muscle damage that is temporary can be caused by a wide range of different drugs and medicines. When myositis from medications occurs it is often diagnosed as myopathy. This is because the muscle inflammation that occurs frequently goes unidentified. Some of the medications and drugs that can cause myositis and myopathy include the following:
- Alcohol
- Statins
- Cocaine
- Colchicine
- Alpha-interferon
- Plaquenil (hydroxychloroquine)
Myositis caused by injury
When untrained groups of muscles are exercised vigorously, it can cause a great deal of swelling, muscle pain, and weakness. In some situations it only lasts a few hours, and in others it can last for several days. It is referred to as myositis due to inflammation being a contributing factor. Rest and recovery are normally the only things needed to recovery from this form of myositis.
Rhabdomyolysis caused from myositis
When the symptoms of myositis are suffered for long periods of time, the breakdown of large muscle groups can occur and result in rhabdomyolysis. When this problem occurs, the urine often appears to be a reddish or dark brown color.
Diagnosing Myositis
A doctor is often able to diagnose myositis by asking questions in reference to the symptoms a patient is experiencing. There are also several other medical tests that may be used as well. Some of the most common tests that many physicians use when diagnosing myositis include the following:
- Electromyography (EMG)
- Blood tests
- Muscle biopsy
- Magnetic resonance imaging (MRI scan)
