Dermatomyositis – Causes, Symptoms, Diagnosis, Treatment

Dermatomyositis is an inflammatory muscle disease distinguished by its involvement with the skin. It is a rare autoimmune disease that normally progresses slowly, but it can progress rather quickly in some circumstances. It affects children and adults, girls, more often than boys.

Causes of Dermatomyositis

Dermatomyositis has no clear cause and is not fully understood. The signature skin rash is caused by inflammation of the small blood vessels just below the surface of the skin that feed muscles and skin. It usually starts in 30-40 years of age and is more common in women as compared to men (2:1 ratio).

While not a genetic disorder, the incidence may be affected by genetic factors.  It is more common in the African population as compared to Caucasians.

Symptoms of Dermatomyositis

Myositis is inflammation of muscles leading to muscle weakness. Distinctive skin involvement is the hallmark of dermatomyositis:

• Muscle weakness: Most commonly affected muscles include those of neck, shoulders, upper arms, hips, and thighs leading to weakness.
• Skin involvement: Itchy, painful reddish/purplish skin rash on the face, eyelids as well as on the elbows, knees, and ankles. The rash may also be rough, dry, and scaly
• Calcinosis – calcium deposits just under the skin that create painful nodules
• Panniculitis – inflammation of fat just under the skin that creates tender bumps

Diagnosis of Dermatomyositis

A diagnosis of Dermatomyositis is made based on a review of the reported symptoms, family medical history, a physical examination, and most often lab tests and a muscle biopsy.

 Lab Tests include:

1. A blood test to measure the presence of creatine kinase (CK), which would normally be high in a patient with dermatomyositis
2. A blood test to look for the presence of antibodies like ANA (antinuclear antibody) and Anti-Mi2
3. An electromyogram, which tests electrical activity in muscles
4. A nerve conduction velocity test, which assesses the speed and strength of nerve impulses

Research suggests that it’s not actually the muscle that is the focus of the autoimmune response, but the blood vessels in the muscle. They become inflamed and constricted and can damage not only muscles but other organs of the body. 

 Heart: There can be inflammation of the heart muscle leading to myocarditis and congestive heart failure.

Lungs: The lung tissue can become scarred leading to interstitial lung disease.

Cancer: There is an increased risk of lung cancer, breast cancer, ovarian cancer or colon cancer.

Esophagus: There can be increased acid reflux or problems with swallowing due to the involvement of esophageal muscles.

Dermatomyositis can also increase the risk of development of other rheumatologic conditions like rheumatoid arthritis, scleroderma, Raynaud’s phenomenon, lupus, etc.

Dermatomyositis is an extremely treatable disease, normally with drugs that suppress the immune system. Patients are also encouraged to use sunscreen and protective clothing when exposed to the sun to reduce the discomfort associated with the skin rash.

• Steroids: It includes medications like prednisone and is usually the first-line treatment.
• Immunosuppressive medications: These include methotrexate and azathioprine
• Hydroxychloroquine: This is used to treat rash associated with Dermatomyositis.

With proper treatment from a rheumatologist, some people experience a full recovery, some people experience greatly reduced symptoms, and some people are required to take medication for the rest of their lives. Most patients experience increased quality of life. In some cases, there is permanent muscle atrophy and loss of strength, while in other cases there is a full recovery of muscle size and strength.

References:

• www.mda.org
• www.myositis.org