What is juvenile dermatomyositis?
Dermatomyositis (DM) is a condition in which inflammation causes muscle weakness and a distinctive rash. The symptoms are very variable and can range from mild to severe. DM can affect individuals at any age but this factsheet focuses on the condition that appears in childhood – juvenile dermatomyositis (JDM). Generally speaking, JDM responds to treatment with medications such as steroids.
JDM belongs to the group of conditions called inflammatory myopathies (also sometimes called myositis). Another inflammatory myopathy called polymyositis is similar to DM but the skin rash is absent.
In this factsheet:
- Who gets juvenile dermatomyositis?
- What are the symptoms?
- What causes juvenile dermatomyositis?
- How is juvenile dermatomyositis diagnosed?
- How is it treated?
- What research is being done?
- Further information
Who gets juvenile dermatomyositis?
JDM is a rare disease – studies have reported that between two to four cases are diagnosed per one million children each year. JDM most often appears between 5 and 15 years of age. Twice as many girls are affected than boys. The condition doesn’t generally run in families but there may be genetic factors that could make some people more likely to develop autoimmune conditions such as JDM.
What are the symptoms?
There is a long list of possible symptoms and complications of JDM but it is important to note that there is a wide range of severity of the condition and it is unlikely that a child will have them all.
Children with JDM develop muscle weakness and pain over a period of days, weeks or even months. The pain can cause the child to be uncharacteristically grumpy which, especially in young children, may be the first symptom that parents notice. The weakness mainly affects the large muscles around the hips and shoulders, resulting in increasing difficulty with walking, climbing stairs, getting up from the floor and lifting the arms. In the most severe cases, the muscle weakness is widespread throughout the body. Fatigue, tiredness, difficulty concentrating, fever and joint pain may also be experienced by children with JDM.
Children with JDM develop skin changes before, after or at the same time as the muscle weakness. The rashes can appear as reddening over the cheeks and upper chest which can be mistaken for sunburn. On the knuckles, elbows and knees, the rash takes the form of patches of red and scaly skin (called Gottron’s papules). The fingernails and the nail beds may take on a pinkish color as well. Sometimes there is a faint ‘violet’ discoloration over the eyelids. There may be some swelling around the eyes and sometimes the skin looks thin and shiny.
Many children complain of difficulty in swallowing and their voice may become ‘nasal’ in quality. Signs of difficulties with feeding, swallowing, coughing and shortness of breath should be looked out for and treatment sought promptly.
One of the less common symptoms is calcinosis – a serious complication affecting 10 to 30 percent of children. This is the development of small hard lumps of calcium under the skin or in the muscle. These lumps can break through the skin, forming ulcers which can get infected.
Inflammation in the digestive tract can also cause bowel difficulties and stomach pain in some children. Heartburn, indigestion, reflux, diarrhea, constipation are some of the digestive complications that can occur as a result. Absorption of medication and nutrients from the digestive system may also be impaired.
Occassionally, in severe cases of JDM, vasculitic ulcers can develop. These are holes in the skin or gastrointestinal tract caused by inflammation of the blood vessels.
Contractures sometimes occur, which are shortened muscles that cause a joint to stay in a bent position or have limited movement.
Less than a quarter of children with JDM develop a complication called “lipodystrophy” which is the loss of body fat. If this is widespread, diabetes and high cholesterol can result.
Sometimes children have symptoms of other autoimmune conditions as well as JDM such as rheumatoid arthritis, scleroderma or lupus. This is called “overlap syndrome”.
Unlike dermatomyositis in adults, JDM is not associated with malignancy (cancer). Heart and lung problems are also less likely in children with JDM.
What causes juvenile dermatomyositis?
The cause of JDM is not well understood. It is known that it is an autoimmune condition, in which the body’s immune system mistakenly attacks small blood vessels in the muscles and under the skin. Inflammatory cells surround the blood vessels which eventually leads to the degeneration of muscle fibers. What causes this autoimmune reaction is still up for debate. It is thought that it is a combination of genetic and environmental factors that trigger the autoimmune reaction.
Although JDM is not considered a genetic disease, there may be some genetic factors that make it more or less likely that an autoimmune condition will develop. Children who develop this disease often have a family history of other autoimmune diseases, such as thyroid disorder, type I diabetes, rheumatoid arthritis, lupus, or Crohn’s disease. In these children with a predisposition to develop JDM, it is thought that exposure to certain environment triggers causes the condition to develop. This could include infection with avirus or bacteria or a heavy dose of sun exposure.
How is dermatomyositis diagnosed?
JDM is very difficult to diagnose and it is so rare that most GPs won’t have ever seen a case. Therefore, it may take a frustratingly long time to get answers. The diagnostic process is started by a careful look at the child’s medical history and a thorough physical exam by a pediatric neurologist, dermatologist and/or rheumatologist.
Blood tests are usually the next step. Nearly all children with JDM will have high levels of creatine kinase (CK) in their blood. This is a protein that normally resides in muscle but leaks out into the blood when the muscles are damaged. A full blood count may show high numbers of white blood cells due to inflammation. Blood tests may also show up antibodies that indicate an autoimmune condition. Antibodies are proteins made by the immune system. However, some children with JDM will have no sign of autoimmune antibodies.
Other tests that may be done to give extra clues and rule out other conditions include:
- magnetic resonance imaging (MRI) which can detect changes suggesting muscle inflammation electromyogram (EMG) which can demonstrate abnormal electrical activity in muscles and help distinguish weakness due to muscle disease from weakness due to nerve problems
- X-rays of the chest or joints. May also be used to look for calcinosis in the arms and legs
ECG and ECHO cardiogram to look at the function of the heart
- Abdominal ultrasound to assess any digestive problems
- Lung function (which may include a CT scan) and swallowing tests
A muscle biopsy is often needed to give an accurate, definitive diagnosis. It involves removing a small piece of muscle through an incision in the skin. The specimen is examined under a microscope for evidence of blood vessels in the muscles being attacked by immune cells.
After diagnosis some of these tests such as blood tests and scans will be done on a regular basis to monitor the response to treatment and look out for any complications that require treatment.
How is it treated?
JDM is a highly treatable disease. Treatment involves drugs to control the inflammation that is causing the muscle weakness and other symptoms. This is usually successful in keeping the symptoms under control and the condition may go into remission either permanently or for a long period of time before more treatment is required. Others with more severe JDM may need more aggressive long-term treatment.
The treatments for JDM work by suppressing the immune system which can increase susceptibility to infections. Medical advice should be sought if illness does occur while taking these drugs and be aware that some vaccines cannot be given while on immunosuppressant medication. No one treatment works for everyone and often a trial and error approach is needed to find the best combination of treatments.
Initial treatment involves high-dose corticosteroids such as prednisolone. Although this is usually effective very quickly, taking these drugs at a high dose for a long period of time carries a high risk of serious side effects. For this reason, the dosage is then tapered to reach an appropriate maintenance dose. However, corticosteroids should never be suddenly stopped or the dose reduced without checking with your doctor first.
Other drugs to suppress the immune system are often given to help reduce the dose of corticosteroid needed. These include:
- Mycophenolate mofetil
Although most people tolerate these medications, some may experience side effects so it is important to be aware of the potential risks and benefits of each drug and work with your doctor to find the most suitable treatment.
IVIg therapy is another treatment option. This is an infusion of immunoglobulins (antibodies) which are extracted from a large pool of donated blood. It is thought that these extra antibodies confuse and interfere with the body’s immune system.
Taking steroids for a long period of time can increase the risk of osteoporosis (brittle bones) so it is important to consider supplements of calcium and vitamin D. In some cases a group of drugs called bisphosphonates may be prescribed to help prevent steroid-induced osteoporosis.
Avoidance of sun exposure during peak hours and use of sunblock and protective clothing are recommended to avoid triggering a flare up of symptoms. Some types of artificial lighting can also affect children with JDM.
Physiotherapy is recommended to keep the joints supple and physiotherapists can supervise an appropriate exercise program. A gentle exercise program, such as hydrotherapy in a swimming pool, can help to maintain strength and fitness. An occupational therapist and/or physiotherapist can help with arranging any mobility aids or equipment that might be required during a flare-up of the condition. Children with JDM tend to tire easily so it is also important for them pace themselves and rest when necessary.
Careful attention to a healthy diet can help with the management of the symptoms, especially when taking corticosteroids which can lead to significant weight gain which can put extra strain on the muscles.
Regular monitoring by a specialist is recommended to allow any complications to be anticipated and treated.
What research is being done?
Much of the research into JDM focuses on understanding precisely why and how the immune system attacks the blood vessels, which will lead to better treatments for the disease.
Several new drugs developed for other autoimmune diseases or for treating people who have had an organ transplant are now being tested for myositis. Some anti-cancer drugs that target cells of the immune system also show promise for inflammatory myopathies. Most of these drugs are so-called “monoclonal antibodies” and have the abbreviation “mab” at the end of their name.
Antibodies are proteins produced by the immune system that target a protein or type of cell in the body and as a result it is destroyed. An antibody preparation that is produced in the laboratory containing identical antibodies is called “monoclonal”. When used as drugs, monoclonal antibodies are designed to target a part of the body that is harmful, for example cancer cells or a component of the immune system that has become overactive in an autoimmune disease.
Tocilizumab is one example of a monoclonal antibody. This drug was developed for rheumatoid arthritis and targets a protein called “interleukin 6 receptor” which plays an important role in immune responses and inflammation. Another is rituximab which was developed to treat blood cancers such as leukemia and works by destroying one type of white blood cell (B cells). Rituximab has also been shown to be effective for a range of autoimmune disorders. The effectiveness of these and other monoclonal antibodies for inflammatory myopathies is currently being tested in clinical trials.
Another drug being tested in clinical trial for myositis is BAF312 (Siponimod). This drug, which was developed by Novartis Pharmaceuticals, acts on the cells of the immune system to inhibit their migration to the location of the inflammation. This, in turn, should lead to reduced inflammation and muscle damage. BAF312 is also clinical trial for multiple sclerosis.
A list of clinical trials for JDM can be found on the clinicaltrials.gov website. Note that some of these studies are “observational” which means that no new drug or treatment is given.
For definitions of any terms that you are not familiar with please take a look at our glossary
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Revised June 2015.
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