What Is Juvenile Myositis?

Juvenile myositis (JM) affects those under the age of 18. JM is known for causing muscle inflammation and skin rashes. These symptoms are the result of ongoing inflammation and swelling of the blood vessels under the skin and in the muscles.

Here is what you need to know about juvenile myositis, including possible causes, types, signs and symptoms, diagnosis, and treatment.

Types of Juvenile Myositis

The most common form of JM is juvenile dermatomyositis (JDM). Juvenile polymyositis (JPM) can also occur in children, but it is much rarer. Benign acute childhood myositis, also called viral myositis, can also affect children.

Juvenile dermatomyositis is characterized by proximal muscle inflammation leading to weakness. It may also affect the blood vessels. The condition affects three out of one million children each year. Most childhood cases start around ages five to 10, and girls are affected twice as often as boys.

Juvenile polymyositis is also characterized by proximal muscle inflammation leading to weakness. It may affect multiple body systems, including the digestive tract, heart, and lungs. JPM is rare, accounting for less than 5% of incidences of JM. It usually develops in early childhood and is more common in girls.

Benign acute childhood myositis usually affects school-age children with an incidence of 2.6 cases per 100,000 children. It is often seen in children recovering from the flu or another respiratory infection. Doctors don’t know whether the muscle symptoms are caused by the virus or by the body’s immune system reaction to the virus.

Juvenile Myositis Symptoms

The symptoms vary by type of juvenile myositis.

Juvenile Dermatomyositis

Early on, JDM may cause some or all of the following symptoms:

• Fever
• Getting tired easily
• Lack of motivation
• Decease in the type or number of physical activities
• Loss of appetite and weight loss
• Choking with eating or drinking
• Muscle pain during and after normal activity
• Muscle tenderness
• Difficulty rising from a sitting position
• Difficulty doing daily activities such as brushing the hair

By the time the parent takes their child in to see the pediatrician, the child has already developed a skin rash and muscle weakness. Muscle pain and weakness usually start slowly.

The skin rash comes on a few weeks after muscle symptoms start. A pediatrician may not recognize the disease early on. In fact, the child could go months with symptoms before a diagnosis is made.

Both skin rash and muscle weakness symptoms result from blood vessel inflammation of the small blood vessels. The digestive tract may also be affected.

Symptoms of JDM can be mild to life-threatening. There are times where a child can experience remission—a period of mild or no symptoms. Serious symptoms of JDM include joint pain and stiffness, contractures, ulcers, and calcium deposits.

Skin Rash

Skin rashes will show up slowly. A parent may notice these on their child’s eyelids or cheeks. The eyelids appear puffy; this symptom may result in a misdiagnosis of allergies.

Red patches of dry skin appear on the knuckles and over the elbows and knees. This type of rash might be misdiagnosed as eczema. The rash is photosensitive and extremely itchy.

Muscle Weakness and Pain

The muscles most commonly affected by JDM are those around the neck, shoulders, hips, belly, and upper legs. The muscles gradually become weak and painful.

Common movements—like climbing stairs—become harder and your child may complain their muscles hurt. Your child may also have less energy.

In severe cases of JDM, the muscles responsible for breathing and swallowing may be affected. That means a child may experience choking with eating or they may easily become short of breath. JDM can also cause the voice to become hoarse.

Call your child’s doctor immediately if you notice any of these severe symptoms.

Joint Pain and Stiffness

Your child may complain of red, sore, stiff, and painful joints. This type of inflammation can be managed with treatment and usually doesn’t cause severe joint damage.

Contractures

A contracture is a condition that causes shortening and hardening of the joints, muscles, tendons, and/or other issues, often causing deformity. This can happen with JDM both early on and during treatment.

When muscles heal, scarring may occur, but stretching exercises through a physical therapy program early on can help reduce the risk for contractures.

Ulcers

Skin and gastrointestinal ulcers can develop in JDM, but they do not occur very often. They are caused by the breakdown of tissue surrounding blood vessels when there is not enough circulation to the tissue.

If your child develops a skin ulcer—regardless of how small—tell your child’s doctor right away. Severe abdominal pain or bloody stools should also be reported immediately.

Calcium Deposits

Some children will JDM may develop calcium deposits—also called calcium nodules—below their skin and in their muscles. These vary in size and feel like firm, small pebbles under the skin.

These nodules may cause muscle movement problems or break through the skin and drain. Contact your child’s doctor if a nodule becomes sore or begins to drain.

Juvenile Polymyositis

JPM characterized by chronic muscle inflammation, tenderness, and weakness that involves the skeletal muscles—the muscles attached to bones by tendons and that produce the movement of body parts.

JPM affects both sides of the body and can make the simplest movements, such as getting out of a car, harder. Sometimes, the distal muscles are affected by JPM—these are the muscles further away from the chest and abdomen and include the lower arms, hands, lower legs, and feet.

More severe symptoms of JPM include:

• Shortness of breath
• Problems swallowing
• Voice changes
• Calcium deposits in the muscles
• Fevers
• Weight loss
• Joint pain and stiffness
• Chronic fatigue
• Heart arrhythmias (abnormal heart rhythms)

Benign Acute Childhood Myositis

Also called viral myositis, benign acute childhood myositis is a mild and limited sudden onset condition that causes lower extremity pain during or following a viral illness. Symptoms include a tiptoe gait, muscle pain, or refusal to walk (due to pain) and low extremity pain that resolves in a matter of days.

Causes

The causes of myositis in children are similar to the causes in adults. But regardless of the type of myositis a child has, something happens that causes the immune system to attack its own healthy muscle tissue.

Events that set off this immune system response include infections, inflammatory conditions, medications, injuries, and a condition called rhabdomyolysis.

Infections

Viruses, such as the flu and the common cold, have long been connected to myositis.

Medications

Many different medications can cause temporary muscle inflammation and damage. Although this is much rarer in children­—because of the medications that cause muscle inflammation and damage are usually not prescribed to children—the most common medications that may cause myositis are cholesterol-lowering drugs called statins.

Myositis may occur right after starting a new medication or after taking the drug for months or years. It can also occur as a result of an interaction between two drugs. Severe myositis caused by medications is rare.

Injury

Sometimes, vigorous exercise can lead to muscle pain and weakness that can last for hours or days. Inflammation is usually the culprit. Myositis symptoms after an injury or exercise tend to resolve quickly with rest and time.

Rhabdomyolysis

This condition is known for causing muscles to break down quickly, resulting in muscle pain, weakness, and inflammation. There are reports of childhood myositis associated with rhabdomyolysis, but these instances are rare.

Diagnosis

The diagnosis of childhood myositis is made the same way an adult diagnosis is made, starting with a medical history and physical exam.

Medical History

Your child's doctor will ask about the child’s general health, including the child’s medical and family history. The child’s doctor may ask the child to describe their symptoms, including exact locations of weakness and pain, and how long these have gone on.

The pediatrician may also want to know if specific things—like food, activity, and weather—make symptoms better or worse, or whether the child had an infection or illness at the time symptoms started.

Physical Examination

The pediatric doctor will examine the child’s skin and test their muscle strength. They will want to know if certain activities are difficult because of muscle weakness. This would include activities like walking up steps and lifting the arms over the head.

Testing and Imaging

In addition to the medical history and physical exam, the child’s doctor may request testing, including:

Blood tests: Bloodwork can look for certain muscle enzymes in the blood from inflamed muscle tissue, as well as specific antibodies that contribute to muscle inflammation and weakness.

Imaging: Magnetic resonance imaging (MRI) can detect inflammation levels in the muscle early on and locate where inflammation is occurring. An electromyogram (EMG) may be done to look for any nerve or muscle damage. Another important modality is an FDG PET CT, which uses nuclear imagining techniques.

Muscle and skin biopsies: A biopsy is the most definitive way to diagnose all types of myositis disease. When muscle or skin tissue affected by myositis is examined under a microscope, inflammatory cells are seen surrounding and damaging the tiny blood vessels within the skin or muscles.

Other diagnostic testing: Other tests may be done to confirm a diagnosis of myositis or to rule other conditions that may have similar symptoms.

Treatment

There is no cure for JM, but the condition is treatable. Treatments can reduce or eliminate symptoms and help your child to lead an active and healthy life. And research on follow up in adulthood finds people diagnosed with JM generally have favorable outcomes, even in instances where disease-related damage occurred.

The goals of treatment for JM are to reduce muscle inflammation and damage, maintain and improve muscle strength, manage pain, and control other disease symptoms.

Another goal is to help your child learn to live with JM. Your child’s treating physician will work with your family to find the best plan for your child. Treatment will include medication, physical therapy, and education.

Medication

Some common medications for treating JM include:

Corticosteroids: These drugs are the first-line treatment for myositis and they work by slowing the body’s autoimmune response, which translates into inflammation and pain reduction and improved muscle strength. Steroids can be given orally, by injection, or intravenously (directly into a vein). Dosage and duration of treatment depend on the severity of symptoms.

Immunosuppressants: Immusuppresssant medications, such as methotrexate, azathioprine, and cyclosporine, work to quiet the immune system. They may be given alone or with hydroxychloroquine (an anti-malaria drug) and mycophenolate mofetil.

Intravenous immune globulin (IVIG): IVIG therapy can slow down the body’s autoimmune response and block harmful antibodies responsible for the inflammation that attacks the muscles and skin.

Other medications: Another medicine used to treat JM include an anti-TNF biologic drug, rituximab.

Physical Therapy

Physical therapy and physical activity are important for children with JM. They can help a child to maintain and increase their muscle strength and flexibility.

Education

Family education on JM may include advice about using sunscreen to prevent irritation and damage to the child’s skin and ways to keep your child active at home and at school. And because JM can affect chewing and swallowing, discussions with a dietitian about healthy and safe eating are also vital.

Treating Benign Acute Childhood Myositis

For benign acute childhood myositis, medication can be given for managing muscle pain. However, no other treatment is necessary for the myositis because symptoms will improve within a few days.

Call your child's doctor if weakness and pain continue, the rash doesn’t go away, or if you see any muscle lumps. You should get immediate medical attention if your child has a fever with muscle pain and weakness, a hot, swollen, and stiff muscle, severe leg pain, or continuing problems with walking.

Fortunately, for most children with viral myositis, outcomes tend to be good, and they are back to walking and playing normally within a few days.

Coping

Children with JM can live life as normally as possible. They can attend school, play sports, and participate in family activities. Exercise will not harm your child and there are no limitations on activities as long as those activities are safe. In fact, being active can help increase muscle strength and endurance, and boost the child's energy levels.

UV light from the sun can trigger symptom flare-ups, so you may want to limit your child’s exposure to the sun. You should apply sunscreen to your child’s skin and have them wear protective clothing when outdoors.

There is no specific diet that a child with JM should follow or any specific foods that may make symptoms worse. Your child can follow a standard, healthy diet.

A Word From Verywell

Juvenile myositis is treatable, and it is very possible for a child can go into remission from JM. However, some children may experience a more active disease and more severe symptoms that may not respond to medications quickly. There is no way of knowing how your child will respond to treatments and how long it will take to find a treatment that works.

The most important thing is for your child to take all their medications and complete physical therapy. And for most children—even those that face bigger challenges—they will grow up to lead full and active lives.