Juvenile Dermatomyositis

Dermatomyositis is in a group of diseases or disorders of the muscles called inflammatory myopathies. The cause of most inflammatory myopathies is unknown; however, the leading theory is that the body's immune system mistakenly directs inflammation against muscle cells and blood vessels in the skin and muscles causing damage, rash, and weakness.

The most common signs and symptoms of JDM include:

• A violet-colored or dusky-red rash, most commonly on the face, eyelids, and areas around the nails, elbows, knees, chest, and back. The rash, which can be patchy with bluish-purple discolorations, is often the first sign of dermatomyositis. A rash on the knuckles occasionally can be misdiagnosed as eczema when in fact it is dermatomyositis.
• Progressive muscle weakness, particularly in the muscles closest to the trunk (such as those in the hips, thighs, shoulders, upper arms, and neck). This can affect the ability to get out of a chair, off the floor or into the car and leads to falls. The weakness affects both the left and right sides of the body equally, and tends to gradually worsen over time if not treated.

Other JDM signs and symptoms that may occur include:

• Difficulty swallowing
• Voice changes
• Muscle pain or tenderness
• Fatigue, fever, and weight loss
• Hardened deposits of calcium under the skin
• Stomach ulcers and intestinal tears
• Lung problems

There are a number of tests doctors may use to help diagnose juvenile dermatomyositis. These tests include:

• Magnetic resonance imaging
  A scanner creates images of the muscles from data generated by a powerful magnetic field and radio waves. It does not involve any radiation exposure. As MRI has become more sensitive, doctors have been using it more frequently to diagnose myositis. MRI can detect subtle muscle inflammation and swelling early in the disease. A benefit of MRI is that it allows us to view whole muscles to look for patterns or patches of muscle inflammation, instead of taking a small sample from a single muscle.
• Muscle biopsy
  Minor surgery is done to remove a small piece of muscle to look at under the microscope. A muscle biopsy may reveal inflammation in the muscles or other problems; it is also helpful to distinguish inflammation from other types of muscle disease such as muscular dystrophy, or infection. In dermatomyositis, inflammatory cells are seen surrounding and damaging the tiny blood vessels within the muscles.
• Blood tests
  A blood test will let the doctor know if enzymes from inflamed muscle are elevated. A blood test also can detect specific autoantibodies (proteins made by the body) associated with JDM, which can help in determining the best medication, treatment, and prognosis.
• Nailfold capillaroscopy
  Abnormal swelling and distortion of the blood vessels around the nails can be seen in most patients with JDM. This finding suggests active disease. Your doctor can examine the nailbeds by using a lighted magnifying tool.

The goal of treatments for juvenile dermatomyositis is to minimize inflammation, improve function, and prevent disability. The treatment should be early and requires a team approach between the rheumatologist, physical therapist, dermatologist, and primary care doctor. JDM is unique among most rheumatic diseases of childhood. Many children have symptoms that do go away with treatment; however, most are not cured.

Corticosteroids
Corticosteroids alter the immune system, limiting the production of antibodies and reducing skin and muscle inflammation, as well as improving muscle strength and function. Corticosteroids, especially prednisone, are usually the first choice in treating inflammatory myopathies such as dermatomyositis, because they work quickly.

The doctor may start with a very high dose, often intravenously (administered directly into vein), and then decrease it as signs and symptoms improve. Signs of improvement may be seen in about two to four weeks as the inflammation decreases, but full recovery will not be seen for months after initiating treatment. Often, physical therapy is required for strengthening and retraining the muscles that were damaged.

Standard treatment for JDM has been high-dose daily oral glucocorticoids (e.g., up to 2 mg/kg/day of prednisone, at times in divided doses), which is continued until clinical and laboratory improvements are evident and then reduced slowly. Intravenous glucocorticoids (methylprednisolone) are also often used at the beginning of therapy. Most patients develop treatment-related side effects with the use of steroids. In many cases, however, prednisone is introduced early as a treatment option and may be discontinued before the two-year period is completed.

Prolonged use of corticosteroids can have serious and wide-ranging side effects, like weight gain, osteoporosis, and cataracts, so the doctor may recommend supplements like calcium and vitamin D to strengthen bone and regular eye exams to detect cataracts.

Corticosteroid-sparing agents
Other medications work more slowly, but have fewer side effects than corticosteroids like prednisone, and allow the patient to wean off steroids sooner (“spare” the steroids).

• Methotrexate is considered best initial treatment for most JDM subjects and is usually started along with corticosteroids.
• Immunoglobulin may be administered through an IV, because it contains healthy antibodies from blood donors. High doses can block the harmful antibodies that attack muscle and skin.
• Other steroid-sparing agents include cyclosporine, azathioprine, tacrolimus, hydroxychloroquine, mycophenalate mofetil, anti-TNF drugs, rituximab or tofacitinib. Any of these may be used in severe diseases along with immunoglobulin, steroids, and methotrexate.

Other aspects of treating juvenile dermatomyositis include:

• Skin protection
  Protection from ultraviolet A and B (UVA and UVB) light is thought to help control the rash and potentially prevent muscle disease. Use sunscreen or sunblock that decreases exposure to UVA and UVB light. Wear wide-brimmed hats and photo-protective clothing. Avoid sun exposure during peak daylight hours.
• Physical therapy
  A physical therapist can teach exercises to maintain and improve strength and flexibility and advise an appropriate level of activity. Physical activity is thought to be important in JDM. Physical therapy is directed at preventing muscle wasting and stiffness, and is particularly necessary in patients with calcium deposits (calcinosis) and muscle involvement. Therapy should focus initially on stretching and splinting and only include more aggressive strength-building therapy once inflammation is controlled.
• Speech therapy
  If the swallowing muscles are weakened by dermatomyositis, speech therapy can help the patient learn how to compensate for those changes.
• Diet assessment
  In JDM, chewing and swallowing can become more difficult. A registered dietitian can teach how to prepare foods that are safe to eat.

Other conditions associated with JDM include diabetes, celiac disease, and arthritis. While many patients with JDM do reach long-term remission without symptoms, some develop a chronic disease; as such, it is important for patients to have good general health practices. These include eating a well-balanced, nutritious diet, maintaining a healthy weight and managing any other chronic illnesses. Regular exercise is important to regain and maintain strength. It is important for employers, teachers, and family members to understand the limitations imposed by muscle weakness, particularly since patients may look entirely normal.