Juvenile myositis is a rare autoimmune disease in which the body’s immune system attacks the body’s healthy and essential tissues. It’s part of a larger grouping of disorders known collectively as “dermatomyositis” and includes juvenile dermatomyositis and juvenile polymyositis. All forms have almost identical symptoms and treatment.
It occurs in two to four children in every million in the United States. The age of onset varies depending on what type of myositis the child has, but it is generally between the ages of four and 12, and it affects girls twice as often as boys.
As far as researchers have been able to ascertain, it is caused by a combination of genetic and environmental factors. Most children with the disease have a family history of autoimmune disorders. Without any known cause, it’s impossible to avoid before the onset.
So why is it still considered juvenile myositis even after the patient has become an adult? The symptoms are very similar, as they fall into the same type of autoimmune disorders, with a few key differences.
Children are more likely to develop calcinosis and joint pain (though this may be because adults have joint pain to begin with). Adults over the age of 50, on the other hand, are more likely to develop cancer in conjunction with the dermatomyositis.
Like with many autoimmune disorders, the potential symptom list is lengthy and overlaps with many other autoimmune disorders and chronic diseases, making it difficult to correctly diagnose without extensive testing.
Note that the muscle weakness varies wildly between patients. It can be as mild as a child being low-energy to as severe as to have trouble breathing.
The rash is often mistaken at first for something else, such as an allergic reaction or eczema. It usually makes its first appearance around the eyes and cheeks. It often also appears on joints, and more rarely, the entire body. It’s important to note that juvenile polymyositis does not exhibit the same rash symptoms that the other forms do, which makes it harder to catch early.
However, it’s important to seek out medical help as soon as possible of juvenile myositis is suspected. Treatment is crucial for recovery.
All of these are direct results of the immune system attacking tissues surrounding the afflicted areas. Vasculitic ulcers are particularly nasty and are associated with more severe cases of juvenile myositis. They usually appear on the skin or in the GI tract, causing additional issues.
Calcinosis, as noted above, is one of the key features of juvenile myositis. This is the development of calcium lumps beneath the skin or in muscles. Around 50-60 % of children with the disorder develop the calcium deposits, ranging in size from a few millimeters across to the size of small pebbles. (These are often reabsorbed by the body during treatment.)
Worrying symptoms include bloody stool, choking or inability to swallow, weakness or loss of voice and abdominal pain. This could indicate that the disorder has caused severe damage to the throat or intestinal tract and may need hospitalization.
Due to the nature of the disease, it can be fatal if it begins to attack critical tissues, such as the heart and lungs. However, this is rare.
There are multiple steps that doctors take before diagnosing someone with juvenile myositis. The first step is a physical examination. Rashes, muscle weakness, fever, and swollen joints are all easy to spot and are early signs of juvenile myositis.
From there, doctors will order blood tests to determine if there are elevated enzymes indicating inflamed muscle tissue, as well as looking for antibodies against the body’s own tissues. If juvenile myositis is suspected, an MRI is done to confirm inflammation and damage to the muscles.
Occasionally a doctor will ask for an electromyogram to get a reading on the electrical activity in the muscles. However, due to its painful nature, it’s not always used.
Finally, a muscle biopsy may be performed, particularly if there are no rashes present – as in juvenile polymyositis. This is important to determine that the muscle weakness is caused by juvenile myositis rather than something else (such as muscular dystrophy). However, if there are rashes and everything else lines up with the disease, a biopsy may not be performed.
As of now, there is no known cure for any form of juvenile myositis. However, there are plenty of treatment options for managing the symptoms and accompanying pain.
A good diet and exercise are crucial for symptom management of this disease. Due to the GI tract issues and sore muscles, not ensuring these two things can make the symptoms much worse.
Treatment depends on the severity of the disease and what symptoms are present. In many cases, prednisone is given to tackle the most common symptoms – rash, pain and fever – though patients have to be closely monitored for side effects. For juvenile dermatomyositis cases, an immunosuppressive drug is also administered. This slows down the immune system – attacking the cause, rather than the symptoms – however, it can have serious side effects, some of which are very similar to the symptoms of juvenile myositis. Further, it often leaves patients susceptible to infection.
Thankfully, most children recover fully within two years of diagnosis – though there are some effects, such as muscle stiffness or weakness, which may stay with them through their entire lives. Younger children tend to recover more rapidly. There is, however, a chance it will come back later in life.
Studies and research are being conducted in search for a cause and cure for the disorders.