Show AllJDM occurs in children under the age of 16 and affects 3,000-5,000 children in the US. Each year there are about 3 new cases of JDM per million people. JDM occurs twice as often in girls as in boys. The average age of onset is 7 years and rarely occurs under the age of 2. JDM found worldwide, but is more frequently seen in North America and it may be more common in the African-American population. There seems to be a clustering of new cases in the spring and summer.
We do not know what causes JDM. Although a number of factors have been investigated, no single factor has been identified as the cause. One view commonly held by researchers in this area (but not scientifically proven) is that myositis requires the combination of two factors- infection and genetics. In this theory, the body has an abnormal response to a virus infection. The immune system attacks and clears the virus, but does not stop this process and begins attacking the body's own tissue(s). There is some evidence to show that some people are more likely to have this type of abnormal immune response and that this tendency for the immune system to act this way is at least partially inherited.
This is not a simple genetic inheritance we see in other types of muscle disease like muscular dystrophy. It is very, very rare for other family members to develop JDM. In some people there appear to be genes, or groups of genes, which either allow the immune system to cause the illness to occur or fail to protect the person from developing it.
We do know that JDM is not contagious. Also, there is nothing you could have done to prevent your child from developing this disease.
In most children, the onset of JDM is characterized by fever in the range of 101-104º and easy fatigue. Almost all children with JDM have less energy and do fewer activities or just refuse to do certain tasks because they know they cannot do them successfully. Weight loss and poor appetite may occur.
The two most characteristic findings in JDM, at the time of diagnosis, are skin rash and muscle weakness. Muscle weakness and pain often begin gradually. The skin rash generally starts in the first few weeks after the onset of muscle symptoms. However, the skin rash may be absent early on and many physicians may fail to recognize this disease during its early stages. JDM often goes unrecognized for several 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 can also be involved sometimes resulting in gastrointestinal symptoms. Symptoms can range from mild to rarely life-threatening. Children with JDM can have times when they have no symptoms, called remission. The following is a list of the most common findings seen in JDM patients.
a) Skin Rash- the first sign of JDM is often slow development of a skin rash. You may notice your child's eyelids and cheeks become red or purplish, and the eyelids may become puffy. This may be misdiagnosed as allergies. Red patches that look like dry skin appear over the knuckles, elbows, and knees. This may be misdiagnosed as eczema. The gets worse in sunlight.
b) Muscle Weakness- the muscles closer to the trunk (neck, shoulders, hips) will slowly become very weak. Common movements like climbing stairs and getting up from the floor or chair may become difficult. Your child may complain that their muscles are sore and that they have less energy. In very severe cases of JDM, the muscles used for swallowing can be affected. This can result in choking on food. Your child's voice may also sound faint. If you notice these symptoms happening, contact the doctor immediately.
c) Stiff and Swollen Joints- your child may complain of stiff and sore joints. The joints, or the muscles around them, may become inflamed. The inflammation doesn't usually last long or cause joint damage.
d) Contractures- a contracture is a shortened muscle that causes a joint to remain in a bent position. This can happen during the healing process (as the muscle heals, it may scar) or through lack of exercise. Contractures can be avoided by daily exercises and physical therapy.
e) Ulcers- the ulcers in JDM are caused by breakdown of the tissue surrounding an involved blood vessel that is not providing enough circulation to the tissue. These ulcers most commonly occur in the skin and gastrointestinal tract. When they occur in the skin, they are sores that have a crater like appearance with an obvious border to the ulcer. These ulcers are very slow to heal and do not scab easily. They vary in severity of pain 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 so that treatment can be started. JDM related ulcers can occur in any part of the gastrointestinal tract (from the esophagus to the rectum). Your child may complain of 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 occur in your child you need to contact your doctor immediately.
f) Calcium Deposits- Some children with JDM develop calcium deposits under the skin or in the muscle. The calcium deposits vary in size but are always firm feeling- like little rocks under the skin. Deposits in the muscle can impair 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 this happens.
There is no specific blood test for JDM. To make the diagnosis of JDM requires a combination of information from different sources. The doctor will ask many questions about your child's symptoms (for example, when did the symptoms start?) and perform a detailed physical examination paying special attention to skin and muscles. The doctor will check for rash involving the eyelids, face, knuckles, knees and elbows. The doctor will also perform a muscle strength exam. Lab tests (blood and urine) will be performed. The most characteristic finding in the lab tests is increased level of one or more muscle related enzymes (for example CPK, aldolase, SGOT). MRI is a way to view the muscles. MRI does not involve X-ray exposure. MRI can be used to either help make the diagnosis of JDM or to find inflamed muscles most suitable for muscle biopsy. 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 and the pathologist will look at it under the microscope to see if there is any inflammation. Doctors sometimes do not perform muscle biopsies if the child has a typical rash and show muscle weakness and muscle enzyme elevation in the blood tests.
There is no cure for JDM. However, there are effective treatments that can reduce or eliminate the symptoms and allow people with JDM to lead active, healthy lives. The goals of any treatment program for JDM are to control muscle inflammation and damage, maintain and improve muscle strength and function, relieve pain, control or prevent other symptoms, and 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. Treatment usually includes medication, physical therapy, and education. As your child's symptoms change, the treatment plan may also be changed. Some common drug therapies are listed below.
- 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 thefirsttreatment for children with JDM in most cases. Prednisone works quickly to suppress the immune system and help 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 gradually reduced. In many cases children will remain on Prednisone for at least two years. Side effects depend on both the dose used and the length of therapy. Common side effects include weight gain, increased appetite, increased risk for infections and facial swelling. 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 try to lower the dose as soon as possible to lessen the side effects, while keeping the disease under control.
- Methotrexate
- For patients with more severe symptoms, that are not controlled by prednisone, or as a treatment to allow for fewer steroids to be used, methotrexate is often used. Methotrexate also suppresses the immune system. Methotrexate is also used to treat cancer but in much higher doses. The effect in the body (both in the way that it effects the immune system as well as side effects) of methotrexate, in the doses used for treatment of children with JDM, are much milder than that seen in treatment of cancer. The doctor will use the lowest dose possible and will usually use it in combination with prednisone. Methotrexate can be given as a pill or by injection. It is given once a week. Common side effects include mouth sores and stomach upset, which can be controlled by taking a vitamin called folic acid. Less common side effects include increased liver enzymes and an increased risk of getting infections.
- Hydroxychloroquine (brand name of drug is Plaquenil)
- Hydroxychloroquine is a drug that is often used to treat the rash in children with JDM. The drug is given as a pill, usually once a day, and is given in combination with other drugs that control the other symptoms in children with JDM. Hydroxychloroquine is generally tolerated very well. Some children will develop stomach upset. About 1 in every 3000-5000 people who take Hydroxychloroquine will accumulate pigment in the retina of the eye. If this is allowed to progress then it could interfere with a person's vision. For this reason, an ophthalmologist (eye doctor) needs to check your child's eyes every six months while your child is taking Hydroxychloroquine. If the eye doctor detects 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 immune suppressive drug that was originally developed for organ transplantation. Cyclosporine, in combination with Methotrexate, can help lower the prednisone dose without causing 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.
- 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 which are proteins that the body's immune system uses to fight infection. The mechanism of action is unclear, but 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 usually once a month. Side effects like headache, fever, and vomiting can occur, but they are usually prevented by pretreating with Tylenol, Benadryl, and sometimes the addition of a steroid.
- Mycophenolate Mofetil (Cellcept)
- Cellcept is a medication that is becoming increasingly used to treat severe disease that is not adequately controlled by the medications listed above. Cellcept is a powerful immune suppressive drug that is also 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 gastrointestinal effects and increased risk of infection. While taking this medication, your child’s doctor will frequently monitor blood cell counts to make sure the risk of infection does not become too great. This medicine can often be very effective in sparing steroids.
JDM is a treatable disease. Most children go into remission within two years and may have their medications eliminated. However, some children may have active disease longer than two years, and some may have more severe symptoms than others. Some children with JDM can have repeat episodes of the disease or may have the type of disease that does not easily respond to medications. It is impossible at this time to predict how your child will respond. The most important thing is to take all the medicine your doctor prescribes and perform physical therapy. Despite the challenges children with JDM and their families face, the majority of children grow up to lead an active, productive life.
