Juvenile dermatomyositis (JDM) is a disease in children that causes skin rash (dermato) and muscle inflammation (myositis). It results in weak muscles.

JDM is a type of autoimmune disease. The immune system is a group of cells that protect the body from infections. In autoimmune diseases such as JDM, these cells fight the body's own tissues and cells. This causes inflammation and sometimes tissue damage.

Frequency of JDM

JDM starts in children under the age of 16. It affects 3,000-5,000 children in the United States. JDM happens twice as often in girls as in boys. The average age the disease starts is 7 years. It is very uncommon for it to start before the age of 2. JDM may last into adulthood.

JDM is found worldwide. New cases seem to be more common in the spring and summer.

Causes of JDM

We do not know what causes JDM. Many factors have been looked into. No one factor has been found as the reason for JDM.

Researchers think that to get JDM, a person may need two things present. These two things are infection and genetics. With this idea, the body has an unusual response to a virus infection. The immune system attacks and gets rid of virus, but the immune system also starts attacking the muscle and skin tissue.

This is more likely to happen in certain people based on their genetics.

It is very rare for other family members to develop JDM and JDM is not contagious. There is nothing you could have done more or less of to stop your child from developing this disease. It is not your fault your child got JDM.

Signs and Symptoms of JDM

At the start of JDM, children may have some or all of these things:

• Fever of 101-104º
• Get tired easily or quicker than friends or siblings
• Not interested in doing things as they are too tired
• Decrease in the type or number of physical activities
• Does not feel hungry
• Chokes while eating food or drinking
• Weight loss
• Pain in the muscles during or after normal activity
• Muscles are tender to touch

When children are diagnosed with JDM, the two most common symptoms are skin rash and muscle weakness. Muscle weakness and pain often start slowly. The skin rash starts in the first few weeks after muscle symptoms begin. However, the skin rash may not be seen until a few weeks later. Many physicians may not recognize this disease during its early stages. JDM often does not get diagnosed for months after the onset of symptoms.

The skin rash and muscle weakness are caused by involvement of the blood vessels in the skin and muscles. Blood vessels in the digestive tract may also be involved. This may result in choking with eating or drinking, pain in the stomach or blood in the stools Symptoms can be mild to life-threatening. Children with JDM can have times when they have no symptoms. This is called remission. Below is a list of the most common findings seen in JDM patients.

Skin Rash

The first sign of JDM is often a skin rash. This will show up slowly. You may notice your child's eyelids and cheeks turn red or purplish. The eyelids may be puffy. This may be misdiagnosed as allergies. Red patches that look like dry skin appear over the knuckles. They may also be seen over the elbows and knees. This may be misdiagnosed as eczema. The rash may get worse in sunlight.

Muscle Weakness

The muscles around the neck, shoulders, belly, hips and upper legs) will slowly become very weak. Common movements (like climbing stairs and getting up from the floor or chair) may be difficult. Your child may complain that his or her muscles are sore. Your child may say that they have less energy.

In very severe cases of JDM, the muscles used for swallowing and breathing can be affected. This can result in choking on food. Your child's voice may also sound faint or hoarse. They may become short of breath easily. Contact the doctor immediately if you notice any of these problems.

Stiff and Swollen Joints

Your child may complain of stiff and sore joints. The joints may become red, sore and painful. The inflammation doesn't last long after treatment is started. It does not cause joint damage.

Contractures

A contracture is a shortened muscle that causes a joint to remain in a bent position. This can happen very quickly during the disease development. It may also happen during the healing process. As the muscle heals, it may scar. Contractures can be decreased by having the child do daily stretching exercises very early in treatment. The stretches are part of the physical therapy treatment program.

Ulcers

Ulcers can develop in JDM. They are caused by breakdown of the tissue surrounding a blood vessel that is not providing enough circulation to the tissue. Ulcers do not occur very often in children with JDM.

The most common locations of ulcers are in the skin and gastrointestinal tract. JDM-related ulcers can occur in any part of the gastrointestinal tract (from the esophagus to the rectum) When they happen in the skin, they are sores that have a crater like look with a clear border to the ulcer. These ulcers are very slow to heal. They do not scab easily. They vary from painless to very painful.

If a child with JDM develops an ulcer, even a very small one, you need to tell your child's doctors quickly. Treatment needs to be started right away.

Your child may have pain with swallowing, severe abdominal pain, or bloody stools. In some cases, there is very little pain but just dark or bloody stools. If any of these happen with your child, contact your doctor right away.

Calcium Deposits

Some children with JDM develop calcium deposits under the skin or in the muscle. The calcium deposits vary in size. They feel firm, like little rocks under the skin.

Calcium deposits in the muscle can cause problems with muscle movement. In some cases, these calcium deposits will break through the skin and drain. These draining areas may become infected.

Contact your doctor if a calcium nodule becomes red, sore or begins to drain.

Diagnosis of JDM

There is no specific blood test for JDM. A variety of information from different sources is needed to make a JDM diagnosis.

The doctor will ask many questions about your child's symptoms. The doctor will complete a detailed physical examination. They will pay special attention to skin and muscles. The doctor will check for a rash involving the eyelids, face, knuckles, knees and elbows. The doctor will also complete a muscle strength exam.

Lab tests of blood and urine will be completed. The most common finding in the lab tests is increased level of one or more muscle related enzymes. These include CPK, aldolase, SGOT, SGPT, LDH.

Magnetic resonance imaging (MRI) is a way to view the muscles. MRI does not involve X-ray exposure. MRI can be used to help make the diagnosis of JDM. It can also be used to find inflamed muscles most appropriate for muscle biopsy. A muscle biopsy gives the most specific information about your child's inflamed muscles and blood vessels. If your child needs a biopsy, the surgeon will remove a small piece of muscle. Your child will be fully asleep during the surgery. Then the pathologist will look at it under the microscope to see if there is any inflammation. This information is very important in making the diagnosis. It helps the doctor know how long the inflammation has been present. It also helps to see the amount of tissue inflammation and damage. This biopsy can predict the chance of certain complications of JDM. Doctors sometimes do not perform muscle biopsies if the child has a typical rash, typical pattern of muscle weakness, typical MRI and muscle enzyme elevation in the blood tests.

Treatment for JDM

There is no cure for JDM. However, there are treatments that can reduce or eliminate the symptoms. This allows people with JDM to lead active, healthy lives.

The goals of any treatment program for JDM are to control muscle inflammation and damage and maintain and improve muscle strength and function. Other goals are to treat pain and control or prevent other symptoms, and to help the child and the family learn to live with the illness.

To reach these goals, doctors work with families to find a treatment plan that works best for them. Treatments include medication, physical therapy, and education. As your child's symptoms change, the treatment plan may also be changed. Some common drug therapies include:

Prednisone

Prednisone is the most commonly used drug in the group of medications called steroids, corticosteroids, or glucocorticoids. Other drugs in this group are Solumedrol or Prednisolone. Prednisone (or one of the other steroids) is the first treatment for children with JDM in most cases. Prednisone works quickly to control inflammation in the muscles, joints, and skin.

This drug is similar to cortisone, a hormone produced naturally in the body. At first, high doses of this drug are given until your child's muscle enzyme tests and strength improve. As your child gets better, the dose will be slowly reduced. In most cases children will remain on prednisone for at least two years.

Side effects of prednisone depend on both the dose used and the length of therapy. Common side effects include weight gain, increased appetite, mood changes, increased risk for infections and facial swelling. Prednisone suppresses the immune system. This is important in suppressing the inflammation. But it also increases the risk for infection. The amount of immune suppression is related to the dose. Over a long period of time, the drug can also cause decreased calcium content in the bones, cataracts, high blood pressure, and slowed growth rate. The doctor will lower the dose as soon as possible and may also start other medications to help control the JDM so to decrease the prednisone side effects, while keeping the disease under control.

Methotrexate

For almost all patients with JDM, methotrexate is started at the same time or very soon after prednisone. Methotrexate is used to help control JDM. It also decreases the amount of steroids needed. Methotrexate suppresses the immune system. Methotrexate is also used to treat cancer but in much higher doses. Methotrexate has been used in the treatment of children with JDM for over 30 years.

The side effects from methotrexate in children with JDM are less common and milder than when used to treat children with cancer. It will be used with prednisone. Methotrexate can be given as a pill or by injection just under the skin like an insulin or allergy shot. It is given once a week.

Common side effects include nausea, feeling tired for about 12-24 hours after the weekly dose and mouth sores. Folic acid is a vitamin that can make the side effects better. Less common side effects are increased liver enzymes and an increased risk of getting infections.

Hydroxychloroquine (brand name Plaquenil)

Hydroxychloroquine is a drug that is used to treat the rash in children with JDM. The drug is given as a pill. It is given once a day. It is given along with other drugs that help control other symptoms in children with JDM.

Hydroxychloroquine is generally tolerated very well. Some children will have stomach upset. About one in every 3,000-5,000 people who take hydroxychloroquine will gather pigment in the retina of the eye. If this continues, it could interfere with a person's vision. For this reason, an eye doctor needs to check your child's eyes every 12 months while your child is taking hydroxychloroquine. If the eye doctor finds any pigment accumulation, the hydroxychloroquine will be stopped before any visual problems develop.

Cyclosporine (brand names Neoral or Sandimmune)

If prednisone and methotrexate don't fully control your child's JDM, your doctor may use cyclosporine. This is another type of drug that decreases inflammation by suppressing the abnormal immune response in children with JDM. It was originally developed for organ transplants. Cyclosporine, along with methotrexate, can help better control the inflammation. This means that lower prednisone doses can be used with less risk for repeat episodes of disease.

Side effects that may occur include extra hair growth on the face and arms, swelling of gums, and high blood pressure. It can also injure the kidney.

Intravenous Immunoglobulin (IVIG)

IVIG is a blood-derived product that has been used in the treatment of children with JDM. IVIG consists of purified antibodies. Antibodies are proteins that the body's immune system uses to fight infection. IVIG has been shown to slow down the inflammatory process. IVIG is given through a needle into a vein (intravenous or IV) in the hospital once a month.

Side effects like headache, fever, and vomiting can occur. They can be prevented by pretreating with Tylenol, Benadryl, and sometimes the addition of a steroid.

Mycophenolate Mofetil (Cellcept)

Cellcept is a medication that is used more often to treat severe disease if it is not well controlled by the medications listed above. Cellcept is a powerful immune suppressive drug that is used to treat severe lupus and other autoimmune diseases. It comes as a capsule, pill, or liquid and is taken twice a day.

Side effects include nausea, abdominal pain and increased risk of infection. While taking this medication, your child’s doctor will regularly monitor blood cell counts. This is done to make sure the risk of infection does not become too great. This medicine can be very helpful in lowering prednisone doses.

Other therapies

Sun exposure can make the rash worse or develop in new areas for many children with JDM. Severe sun exposure can make the overall disease worse. It is important that a sunscreen made with zinc and titanium of at least SPF 30 is used every day the child is outside, including winter. It should be reapplied every two hours to all areas of the skin that are not covered by clothing.

The treatments described here are the most commonly used. In addition, new treatments are being tested in the treatment of JDM. You should discuss all treatment options with your child’s doctor.

Long-Term Outlook for Children with JDM

JDM is a treatable disease. In many cases the disease goes into remission within two years. The child may have their medications stopped.

However, some children may have active disease longer than two years. Some children may have more severe symptoms than others.

Some children with JDM can have repeat episodes of the disease. Some may have the type of disease that does not respond quickly to medications.

It is impossible at this time to know how your child will respond. The most important thing is to take all the medicine your doctor prescribes and complete physical therapy.

Even with the challenges children with JDM and their families face, the majority of children grow up to lead an active, productive life.