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Dermatomyositis

Idiopathic inflammatory myopathy, Juvenile dermatomyositis, Juvenile polymyositis, Secondary glomerular disease

Overview

Dermatomyositis is one of a group of acquired muscle diseases called inflammatory myopathies (disorder of muscle tissue or muscles), which are characterized by chronic muscle inflammation accompanied by muscle weakness. The cardinal symptom is a skin rash that precedes or accompanies progressive muscle weakness. Dermatomyositis may occur at any age, but is most common in adults in their late 40s to early 60s, or children between 5 and 15 years of age. There is no cure for dermatomyositis, but the symptoms can be treated. Options include medication, physical therapy, exercise, heat therapy (including microwave and ultrasound), orthotics and assistive devices, and rest. The cause of dermatomyositis is unknown.

Symptoms - Dermatomyositis

The signs and symptoms of dermatomyositis may appear suddenly or develop gradually, over weeks or months. The cardinal symptom of dermatomyositis is a skin rash that precedes or accompanies progressive muscle weakness. The rash looks patchy, with bluish-purple or red discolorations, and characteristically develops on the eyelids and on muscles used to extend or straighten joints, including knuckles, elbows, heels, and toes. Red rashes may also occur on the face, neck, shoulders, upper chest, back, and other locations, and there may be swelling in the affected areas. The rash sometimes occurs without obvious muscle involvement.

Adults with dermatomyositis may experience weight loss or a low-grade fever, have inflamed lungs, and be sensitive to light. Children and adults with dermatomyositis may develop calcium deposits, which appear as hard bumps under the skin or in the muscle (called calcinosis). Calcinosis most often occurs 1-3 years after the disease begins. These deposits are seen more often in children with dermatomyositis than in adults. In some cases of dermatomyositis, distal muscles (muscles located away from the trunk of the body, such as those in the forearms and around the ankles and wrists) may be affected as the disease progresses. Dermatomyositis may be associated with collagen-vascular or autoimmune diseases, such as lupus. 

Signs and Symptoms:

  • Abnormality of the eye
  • Autoimmunity
  • EMG abnormality
  • Muscle weakness
  • Myalgia
  • Periorbital edema

Causes - Dermatomyositis

The cause of this disorder is unknown. It is theorized that an autoimmune reaction (reactions caused by an immune response against the body's own tissues) or a viral infection of the skeletal muscle may cause the disease. In addition, some doctors think certain people may have a genetic susceptibility to the disease.

Small blood vessels in muscular tissue are particularly affected in dermatomyositis. Inflammatory cells surround the blood vessels and eventually lead to degeneration of muscle fibers.

Possible complications of dermatomyositis include:

  • Difficulty swallowing. If the muscles in your esophagus are affected, you may have problems swallowing (dysphagia), which in turn may cause weight loss and malnutrition.
  • Aspiration pneumonia. Difficulty swallowing may also cause you to breathe food or liquids, including saliva, into your lungs (aspiration), which can lead to pneumonia.
  • Breathing problems. If your chest muscles are affected by the disease, you may experience breathing problems, such as shortness of breath.
  • Calcium deposits. Deposits of calcium can occur in your muscles, skin and connective tissues (calcinosis) as the disease progresses. These deposits develop earlier and are more common in children with dermatomyositis.

Associated conditions:

Dermatomyositis may cause other conditions or put you at higher risk of developing them. These conditions include:

  • Raynaud's phenomenon. This is a condition in which your fingers, toes, cheeks, nose and ears turn pale when exposed to cold temperatures.
  • Other connective tissue diseases. Other conditions, such as lupus, rheumatoid arthritis, scleroderma and Sjogren's syndrome, can occur in combination with dermatomyositis.
  • Cardiovascular disease. Dermatomyositis may cause the muscular walls of your heart to become inflamed (myocarditis). In a small number of people who have dermatomyositis, congestive heart failure and heart arrhythmias may develop.
  • Lung disease. A condition called interstitial lung disease may occur with dermatomyositis. Interstitial lung disease refers to a group of disorders that cause scarring (fibrosis) of lung tissue, making the lungs stiff and inelastic. Signs and symptoms include a dry cough and shortness of breath.
  • Cancer. Dermatomyositis in adults has been linked to an increased likelihood of developing cancer, particularly of the cervix, lungs, pancreas, breasts, ovaries and gastrointestinal tract. Risk of cancer increases with age, although it appears to level off three years or so after a diagnosis of dermatomyositis. The diagnosis of cancer may also happen before you develop dermatomyositis.

Prevention - Dermatomyositis

Not supplied.

Diagnosis - Dermatomyositis

Following tests to diagnosis the disease:

  • Blood analysis. A blood test will let your doctor know if you have elevated levels of muscle enzymes, such as creatine kinase (CK) and aldolase. Increased CK and aldolase levels can indicate muscle damage. A blood test can also detect specific autoantibodies associated with different symptoms of dermatomyositis, which can help in determining the best medication and treatment.
  • Chest X-ray. This simple test can check for signs of the type of lung damage that sometimes occurs with dermatomyositis.
  • Electromyography. A doctor with specialized training inserts a thin needle electrode through the skin into the muscle to be tested. Electrical activity is measured as you relax or tighten the muscle, and changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine the distribution of the disease by testing different muscles.
  • Magnetic resonance imaging (MRI). A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. Unlike a muscle biopsy, an MRI can assess inflammation over a large area of muscle.
  • Skin or muscle biopsy. A small piece of skin or muscle is removed for laboratory analysis. A skin sample can confirm the diagnosis of dermatomyositis and rule out other disorders, such as lupus. A muscle biopsy may reveal inflammation in your muscles or other problems, like damage or infection. If the skin biopsy confirms the diagnosis, a muscle biopsy may not be necessary.

Prognosis - Dermatomyositis

Most cases of dermatomyositis respond to therapy. Some people may recover and have symptoms completely disappear. This is more common in children. In adults, death may result from severe and prolonged muscle weakness, malnutrition, pneumonia, or lung failure. The outcome is usually worse if the heart or lungs are involved. 

Thus, it is important that treatment begin as soon as possible. The cutaneous manifestations of dermatomyositis may or may not improve with therapy in parallel with the improvement of the myositis. In some patients the weakness and rash resolve together. In others, the two are not linked, with one or the other being more challenging to control. Often, cutaneous disease persists after adequate control of the muscle disease.

Treatment - Dermatomyositis

There is no cure for dermatomyositis, the symptoms can be treated. Options include medication, physical therapy, exercise, heat therapy (including microwave and ultrasound), orthotics and assistive devices, and rest. The treatment can improve your skin and your muscle strength and function. The earlier treatment is started in the course of dermatomyositis, the more effective it is — leading to fewer complications.

However, as with many conditions, no single approach is best; your doctor will tailor your treatment strategy based on your symptoms and how well they respond to therapy.

Medications:

The most commonly used medications to treat dermatomyositis include:

  • Corticosteroids. Drugs such as prednisone can be very effective in controlling dermatomyositis symptoms. But prolonged use of these drugs can have serious and wide-ranging side effects, which is why your doctor may gradually taper the dose of medication down to lower levels.
  • Corticosteroid-sparing agents. When used in combination with a corticosteroid, these drugs can decrease the dose and potential side effects of the corticosteroid. The two most common medications used for dermatomyositis are azathioprine (Azasan, Imuran) and methotrexate (Trexall).
  • Rituximab (Rituxan). More commonly used to treat rheumatoid arthritis, rituximab is an option if initial therapies don't adequately control your dermatomyositis symptoms.
  • Antimalarial medications. For a persistent rash, your doctor may prescribe an antimalarial medication, such as hydroxychloroquine (Plaquenil).


Therapy:

Depending on the severity of your symptoms, your doctor might suggest:

  • Physical therapy. A physical therapist can show you exercises to maintain and improve your strength and flexibility and advise an appropriate level of activity.
  • Speech therapy. If your swallowing muscles are weakened by dermatomyositis, speech therapy can help you learn how to compensate for those changes.
  • Dietetic assessment. Later in the course of dermatomyositis, chewing and swallowing can become more difficult. A registered dietitian can teach you how to prepare easy-to-eat foods.

Surgical and other procedures:

  • Intravenous immunoglobulin (IVIg). IVIg is a purified blood product that contains healthy antibodies from thousands of blood donors. These healthy antibodies can block the damaging antibodies that attack muscle and skin in dermatomyositis. Given as an infusion through a vein, IVIg treatments are expensive and may need to be repeated regularly for the effects to continue.
  • Surgery. Surgery may be an option to remove painful calcium deposits and prevent recurrent skin infections.

Resources - Dermatomyositis

  • NIH
  • Mayo Clinic
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