An Overview of Myositis

Myositis literally means “muscle inflammation.” The term myositis also describes the group of conditions—called inflammatory myopathies—that cause chronic muscle inflammation, damage, weakness, and (sometimes) pain.

Myositis-type inflammation is caused by lymphocytes, white blood cells that typically protect the body’s immune system. With myositis, lymphocytes and foreign substances invade healthy muscle fibers. Chronic (ongoing) inflammation, over time, destroys muscle fibers, causing muscle function loss, immobility, and fatigue.

Because of its rarity, a diagnosis of myositis isn’t always easy to make, and the cause of it is not always known. According to The Myositis Association, all forms of myositis affect an estimated 50,000 to 75,000 Americans. While the condition has no cure, it is treatable.

Here is what you need to know about myositis, including the types, symptoms, causes, and treatment.

Types and Symptoms

Myositis takes many forms, including polymyositis, dermatomyositis, inclusion body myositis, immune-mediated necrotizing myopathy, antisynthetase syndrome, and juvenile myositis. There are other forms of myositis, but they are considered much more rare.

Many types of myositis are autoimmune diseases, conditions where the body’s immune system attacks and damages its own tissues.

Polymyositis

Polymyositis causes muscle weakness on both sides of the body. Having polymyositis makes it hard to climb steps, get up from a seated position, reach overhead, and lift. It can affect anyone of any age, but is more common in adults ages 31 to 60 years of age, women, and people of color.

Symptoms of polymyositis develop gradually over weeks or months, and may include: 

• Inflammation and weakness in the muscles responsible for movement
• Weakness in the proximal muscles—those closest to the chest and abdomen, although the distal muscles (lower arms, hands, lower legs, feet, etc.) may be affected as the disease progresses
• Arthritis, including mild joint or muscle tenderness
• Shortness of breath
• Problems with swallowing and speaking
• Fatigue
• Heart arrhythmias—improper heart rhythm, whether irregular, too fast, or too slow

Dermatomyositis

Dermatomyositis (DM) is easier to diagnose than other types of myositis. It is distinguishable because of the purple-red, patchy-like rashes it causes. These rashes appear on the eyelids, face, chest, neck, and back.

Rashes may also appear on the knuckles, toes, knees, and elbows. Muscle weakness often follows. 

This type of myositis can affect anyone of any age, but it is most common in adults in their late 40s to early 60s and in children ages 5 to 15.

Other symptoms of DM include:

• Joint inflammation
• Muscle pain
• Nail bed abnormalities
• Rough, dry skin
• Calcium lumps under skin
• Gottron papules—bumps found over the knuckles, elbows, and knees; may have a raised, scaly look
• Trouble getting up from a seated position
• Fatigue
• Weakness of the neck, hip, back, and shoulder muscles
• Problems swallowing and voice hoarseness
• Weight loss
• Low-grade fever
• Inflamed lungs
• Sensitivity to light

Inclusion Body Myositis

Inclusion body myositis (IBM) affects more men than women, and most people who develop this condition are over age 50. Initial symptoms of IBM include muscle weakness in the wrists and fingers. IBM may also cause weakness in the thighs, but is more prominent in the smaller muscles.

This type of myositis is often asymmetrical, meaning it affects one side of the body more than the other.

Causes of IBM are not understood, but researchers believe a combination of genetic, immune-related, and environmental factors are involved in its development. Some people have certain genes that predispose them to the condition, but IBM is not necessarily inherited.

In addition to muscle weakness, IBM may cause:

• Problems with walking, including frequent falls, tripping, and loss of balance
• Trouble getting up from a seated position
• Problems swallowing
• Muscle pain
• Loss of deep tendon reflexes

Immune-Mediated Nercotizing Myopathy

Immune-mediated necrotizing myopathy (IMNM)—also called necrotizing myopathy or necrotizing autoimmune myopathy—is a rare type of myositis characterized by necrosis (cell death). IMNM is so rare that there have only been 300 reported cases to date.

Symptoms of IMNM are similar to those of other types of myositis and may include:

• Weakness in the muscles closest to the center of the body—forearms, thighs, hips, back, neck, and shoulders
• Struggles with climbing steps, standing up from a sitting position, and lifting arms over the head
• Falling and struggles with getting up from falls
• General fatigue

What makes IMNM different from other types of myositis is that people with this type have less inflammation and increased evidence of necrosis. Researchers have been unable to determine potential causes, but think certain autoantibodies play a role in its development.

Autoantibodies are proteins produced in the immune system that mistakenly target the body’s own tissues. Much like other types of myositis, there is no cure for IMNM, but the condition is treatable.

Antisynthetase Syndrome

Antisynthetase syndrome is known for causing muscle and joint inflammation, interstitial lung disease (ILD), thickening and cracking of the hands (mechanic’s hands), and Raynaud’s syndrome.

Interstitial lung disease is usually one of the first or only symptoms of this type of myositis. ILD is an umbrella term for a group of disorders that cause fibrosis—scarring of the lungs.

Fibrosis causes stiffness in the lungs that affects breathing. Raynaud’s syndrome causes fingers or toes to be discolored after being exposed to temperature changes or emotional events. 

The exact cause of antisynthetase syndrome is unknown, but the production of certain autoantibodies are believed to be linked to its development. The average age for disease onset is around 50 years, and the condition is more common in women.

Juvenile Myositis

Juvenile myositis (JM) affects children under 18. According to The Myositis Association, JM affects two to four out of every one million children. Girls are more likely to develop JM.

The most common type of JM is juvenile dermatomyositis (JDM), which is characterized by muscle weakness and skin rash. Juvenile polymyositis can also affect children, but is less common.

In addition to muscle weakness, JM may cause:

• Visible reddish-purple rashes over the eyelids or joints
• Fatigue
• Fever
• Stomach aches
• Moodiness and irritability
• Motor function issues, including climbing steps, getting up from a seated position, reaching overhead, and getting dressed
• Trouble lifting the head
• Swelling or redness in the skin around fingernails
• Problems with swallowing
• Voice hoarseness
• Calcium lumps under skin
• Joint and muscle pain
• Gottron’s papules

Causes

Any condition that causes muscle inflammation can lead to myositis. Causes may include inflammatory conditions, infections, medications and drugs, injury, or a condition called rhabdomyolysis which causes muscle breakdown.

• Inflammatory conditions: Conditions that cause systemic (whole-body) inflammation affect the muscles and may result in myositis. Many inflammatory causes are autoimmune diseases, where the body attacks its own healthy tissues. Inflammatory causes are the most serious causes of myositis and require long-term treatment.
• Infection: Viral infections are the most common infective causes of myositis. Bacteria, fungi, and other organisms can also cause myositis, but these cases are more rare. Viruses and bacteria may attack muscle tissue directly or release substances that cause damage to muscle tissue.
• Medications: Many different medications can cause muscle weakness. Medications, such as statins, colchicine, and hydroxychloroquine, can induce different types of myositis. Excessive use of alcohol and illicit drugs can also cause myositis. Myositis may occur at the start of a new medication, or it may occur years after taking a drug. It can also result from a reaction between two medications.
• Injury: Vigorous activity can cause muscle pain, swelling, and weakness for hours or days. Inflammation is the main cause of symptoms in myositis related to injury. The good news is that myositis from mild injury or after exercise usually resolves quickly with rest and pain relievers.
• Rhabdomyolysis: Rhabdomyolysis occurs when muscles break down quickly, leading to the release of muscle fiber materials into the blood. These substances are harmful to the kidneys. Muscle pain, weakness, and swelling are symptoms of this condition.
• Infection: Viral infections are the most common infective causes of myositis. Bacteria, fungi, and other organisms can also cause myositis, but these cases are more rare. Viruses and bacteria may attack muscle tissue directly or release substances that cause damage to muscle tissue.
• Medications: Many different medications can cause muscle weakness. Medications, such as statins, colchicine, and hydroxychloroquine, can induce different types of myositis. Excessive use of alcohol and illicit drugs can also cause myositis. Myositis may occur at the start of a new medication, or it may occur years after taking a drug. It can also result from a reaction between two medications.
• Injury: Vigorous activity can cause muscle pain, swelling, and weakness for hours or days. Inflammation is the main cause of symptoms in myositis related to injury. The good news is that myositis from mild injury or after exercise usually resolves quickly with rest and pain relievers.
• Rhabdomyolysis: Rhabdomyolysis occurs when muscles break down quickly, leading to the release of muscle fiber materials into the blood. These substances are harmful to the kidneys. Muscle pain, weakness, and swelling are symptoms of this condition.

Diagnosis

Make an appointment to see your healthcare provider if you experience ongoing muscle weakness or a rash on the face or knuckles that doesn’t go away. 

Other reasons to contact a practitioner are:

• If you or your child experiences a lump in a muscle, especially if there is fever and/or additional symptoms
• Fever with muscle pain and weakness
• If a child is experiencing severe leg pain and struggling to walk

Testing

A diagnosis of myositis is often difficult to make because the condition is so rare and also because symptoms are common in other conditions. If a healthcare provider suspects myositis, the following tests might be done:

• Bloodwork: High levels of certain enzymes, such as creatine kinase, indicate muscle inflammation. Other bloodwork can look for abnormal antibodies to identify autoimmune diseases.
• Magnetic resonance imaging (MRI): This involves a magnetic scanner and a computer to take pictures of muscle tissues. An MRI scan can help identify muscles affected by myositis and changes in those muscles over time.
• Electromyography (EMG): An EMG measures muscle responses. It is done by inserting needle electrodes into muscles to identify muscles that are weak or damaged by myositis.
• Muscle biopsy: This is the most accurate method for diagnosing myositis. Once a healthcare provider identifies a weak muscle, they make a small incision and remove a small sample of muscle tissue for testing. The tissue sample will be looked at under a microscope. Different chemicals are used on the tissue sample to identify signs of myositis or another disease.

Treatment

Currently, there is no cure for myositis. However, the disease can be managed, and medicinal treatment is helpful for reducing inflammation and keeping muscle weakness from getting worse. Your healthcare provider will also recommend lifestyle changes to help improve strength.

Medicine

Medicinal treatment for myositis involves three types of drugs: corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), and biologic therapies.

Corticosteroids, such as prednisone, are a first-line treatment for myositis. These drugs suppress the immune system to slow down the attack on healthy tissues and treat skin rash.

Treatment with corticosteroids may reduce muscle inflammation and pain, and increase muscle strength. Dosage varies from patient to patient, but healthcare providers prescribe high doses early on and decrease dosage as symptoms improve.

NSAIDs, such as aspirin or ibuprofen, can help reduce inflammation in muscles and surrounding tissues.

When biologic agents are prescribed for treating myositis, they work by suppressing the immune system’s response to bacteria, viruses, and other organisms. When the immune system is suppressed, a person’s risk of infection is increased. Biologic drugs also increase the risk of certain types of cancer.

Lifestyle

Exercise and physical therapy, rest, nutrition, and stress reduction may also help to reduce myositis symptoms.

• Exercise: Regularly stretching can help to maintain your range of motion in weak arms and legs. Before starting any exercise program, talk to your practitioner about suitable exercises. Working with a physical therapist can help you to work toward maintaining function, reducing muscle loss, keeping muscles strong and flexible, and decreasing fall risk associated with myositis.
• Rest: Getting enough rest is another important part of your treatment plan. Take frequent breaks during the day, and try to strike a balance between activity and rest.
• Nutrition: What you eat affects your health overall. While there isn’t a specific diet recommended for myositis, an anti-inflammatory diet is easily adaptable and one that can benefit anyone living with an inflammatory condition.
• Stress reduction: It is important that people with myositis find ways to manage daily stress. You can try relaxation exercises like yoga, breathing exercises, or biofeedback exercises.

A Word From Verywell

The outlook for most types of myositis can be good with proper treatment. But if left untreated, myositis can result in disability or death. That is why it is important to manage symptoms and stay on top of your healthcare provider’s treatment plan.

It is possible to experience remission and periods of low disease activity with proper and continued treatment.