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Dermatomyositis

Dermatomyositis is an acquired disorder due to inflammation in the muscle and skin. Children and adults may both be affected and females are more likely to obtain it than males.

Dermatomyositis Symptoms

The symptoms are weakness, muscle soreness, bumps of calcium deposits under the skin, and a red, scaly rash on the elbows, knees, chest, and face. The presence of the rash usually comes before the muscle weakness, and it helps distinguish the disorder as dermatomyositis. Some patients with dermatomyositis will have troubles swallowing.

The weakness in dermatomyositis usually develops slowly over weeks to months although rare cases can begin over days. This weakness most commonly affects the muscles of the arms and legs. Patients often notice trouble getting out of chairs or climbing stairs. It does not typically involve the muscles of the eyes, heart, or breathing muscles. However the muscles involved in swallowing can become weak as well. Muscle pain may also be a prominent symptom since dermatomyositis is associated with inflammation in the muscles. The rash of dermatomyositis can look very similar to a number of other rash types and by skin biopsy there is nothing that distinguishes dermatomyositis from a host of other skin rashes. In its most typical form the rash maybe reddish and even purplish and extend across the face, chest, fingers and neck. Some patients may even lose their hair. Clinically the appearance if often quite characteristic to neurologists, rheumatologists, and dermatologists.

Dermatomyositis Diagnosis

Nailfold Lesions

The diagnosis of dermatomyositis begins with a neurologist taking the patient's history and performing a clinical exam, especially examining the rashes. A physician who suspects a diagnosis of dermatomyositis may perform blood tests, an EMG, or a magnetic resonance imaging scan (MRI). The blood tests reveal elevated levels of enzymes which are found in muscle. Doctors may check a creatine phoshpokinase (CPK) or an aldolase. Without elevated levels of one of these enzymes it is very unlikey to have a diagnosis of dermatomyositis. The EMG test looks at the function of a patient’s muscles and will reveal evidence for muscle inflammation and muscle damage. An MRI looks for visual evidence for inflammation in a group of muscles. It can also be used to choose which muscle to biopsy.

If these three non-invasive tests suggest a diagnosis of dermatomyositis then patients should have a muscle biopsy before beginning therapy. A muscle biopsy is needed in all patients for a definitive diagnosis. Finally there are a very specific set of blood tests called Myositis Specific Autoantibodies. These antibodies are found in 20-30% of patients with dermatomyositis but are important because they can predict the presence of other associated conditions.

Dermatomyositis Cause

Gottron's Papules

Dermatomyositis is an autoimmune disorder, meaning that a person's white blood cells which are supposed to fight off bacteria and viruses begin attacking their own muscles. While we do not know what triggers a person’s immune system to behave in this way there are many theories that suggest it is a combination of one’s genetic predisposition and environmental exposures. People of either sex or any age can get dermatomyositis, but it is slightly more common in females, and people in middle childhood and their 20s. It is sometimes associated with other autoimmune diseases such as lupus, scleroderma, and rheumatoid arthritis. In rare cases it can be associated with certain types of cancers.

Dermatomyositis Treatment

Muscle Fibers on Edge of Fascicles
are Necrotic and Regenerating

Dermatomyositis is an autoimmune disease and therefore therapy is directed at altering a patient’s immune system. All of these therapies therefore have some significant risk of side effects and treatment needs to be undertaken only with physicians accustomed to using these medications and to monitoring their side effects. Corticosteroids are often used as a first line therapy to treat dermatomyositis because they decrease the muscle inflammation. These can be effective in a matter of weeks. If corticosteroids are ineffective, other immunosuppressive medications may be given such as azathioprine, mycophenylate mofetil, cyclosporine, or methotrexate. Intravenous immunoglobulin has also been shown to be effective in very refractory cases.

Dermatomyositis Cure

In most people once this disease begins there is no clear way to cure the disease. There are however several effective treatments which exist that can improve a person’s muscle strength. In most cases people can resume their usual level of function. Further research is being done and it is hopeful that eventually a cure will be found.