What is juvenile dermatomyositis?

Juvenile dermatomyositis is an inflammatory disease of the skin and muscles. While all ages and ethnic groups can be affected by dermatomyositis, the disorder is most common among children 5 to 14 years old. This condition is rare, affecting three out of 1 million children.

Juvenile dermatomyositis is one of a group of conditions called idiopathic inflammatory myopathies. These conditions are characterized by inflammation of the blood vessels in the skin and muscles.

One of the main symptoms of this condition is skin rash. The rash typically occurs around the eyelids and over the knuckles, finger joints, elbows and knees. The rash can also involve the face, chest and back and can range from mild redness to serious ulcers.

Children with juvenile dermatomyositis also often develop weakness in the large muscles in their neck, shoulders and hips. This can make everyday activities, like climbing stairs, brushing their own hair and getting into cars, more difficult.

Children with the disorder often complain of weakness, tiredness and shortness of breath. They may or may not complain of pain. In some cases, children may have difficulty swallowing or voice changes.

Juvenile dermatomyositis can sometimes involve other organ systems such as the joints, gastrointestinal system, heart, lungs, kidneys and eyes.

Causes

The cause of the inflammatory response in juvenile dermatomyositis remains unknown, but doctors believe that a combination of factors are involved.

Researchers have found that individuals with certain gene variations may be more susceptible to developing the disorder. Environmental factors — such as UV light exposure, respiratory or gastrointestinal infections — may trigger the onset of dermatomyositis in susceptible individuals.

Signs and symptoms

Symptoms of juvenile dermatomyositis may appear suddenly or gradually, and each child may experience symptoms at varying levels at different times.

The most common symptoms of juvenile dermatomyositis include:

• Skin rash on the eyelids, knuckles, finger joints, elbows, knees; the rash may also occur on the face, chest and back
• Muscle weakness, pain and tenderness
• Difficulty swallowing
• Fever
• Fatigue
• General discomfort and irritability
• Weight loss
• Joint pain and swelling
• Calcium deposits under the skin (calcinosis)

Symptoms of juvenile dermatomyositis may resemble other medical conditions or problems. Always consult your child's doctor for a diagnosis.

Phases of juvenile dermatomyositis

The course of juvenile dermatomyositis is often divided into three phases based on symptoms and findings on examination. The three phases include:

• Prodromal period. This phase can last for weeks or months. The symptoms seen during this period are nonspecific and can include fever, fatigue, weight loss, general discomfort and irritability.
• Progressive muscle weakness and rash. During this phase, symptoms include active inflammation causing muscle weakness and rash. Inflammation will continue unless it is treated with medications to suppress the immune system.
• Recovery. Recovery after initiation of immunosuppressive therapy usually occurs over several months, but sometimes may occur over years. Many children recover full muscle strength. However, there may be some residual muscle weakness, atrophy (wasting), or contractures (a condition in which joints become fixed in position or limited in range of motion due to lack of muscle use). Many children have full resolution of rash, but some may experience scarring. Some children may also develop permanent calcinosis. Some children remain in remission and do not experience recurrence of inflammation, but others have episodic flares or persistent inflammation.

Testing and diagnosis

Diagnostic evaluation begins with a thorough medical history and physical examination of your child. At Children’s Hospital of Philadelphia, clinical experts use a variety of diagnostic tests to diagnose juvenile dermatomyositis, including:

• Laboratory tests. These tests are used to assess the presence of antibodies, muscle enzymes, and indicators of inflammation in the blood.
• Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

Sometimes the following tests may be used if more information is needed after the above evaluations:

• Swallowing study to evaluate the function and coordination of swallowing muscles.
• Upper GI study to evaluate the anatomy and function of the upper intestines.
• Electrocardiogram (EKG) to evaluate the electrical activity of the heart.
• Echocardiogram to evaluate heart function.
• Pulmonary function tests to evaluate lung function.
• X-rays to view images of internal tissues, bones and organs.
• Electromyography (EMG) and nerve conduction studies (NCS) to determine nerve or muscle damage.
• Muscle biopsy, in which a small piece of muscle is removed and examined under a microscope.

Treatment

There is no cure for juvenile dermatomyositis. However, with a team approach to treatment, remission of the disease is usually achieved.

Treatment typically includes:

• Medication to treat the inflammatory process (immunosuppression), such as glucocorticosteroids, methotrexate and hydroxychloroquine
• Physical and occupational therapy with the goal of improving muscle function and strength
• Sun protection (sunscreen and sun avoidance), as UV exposure can cause disease flares
• Calcium and vitamin D supplementation to promote bone health

In severe cases, other forms of immunosuppressive treatment may be needed. 

Follow-up care

Children with dermatomyositis will need ongoing care by a pediatric rheumatologist to monitor their disease, medications and treatment plan. Regular bloodwork can help doctors determine if treatment medications need to be adjusted.

Children taking hydroxychloroquine should have a yearly eye exam with an ophthalmologist to check for medication toxicity. Children on chronic steroids may also by treated by an endocrinologist to monitor and treat overall growth and bone health issues.

Outlook

With early treatment and appropriate follow-up care, many children with dermatomyositis will fully recover their strength, get back to their regular activities, and have a normal lifespan.

A small percentage of children with the disorder will become permanently disabled because of muscle contractures and calcinosis. The mortality rate for the disorder is low (1-3 percent), and most fatalities are caused by severe involvement of the gastrointestinal system, heart and lungs.

We are not yet able to fully predict the course of dermatomyositis for every child, but research is ongoing. Clinicians expect that increased understanding of juvenile dermatomyositis and newer treatment options will further improve the lives of children with the disease.