Dermatomyositis

What is Dermatomyositis?

Dermatomyositis is a disorder in which there is chronic inflammation of skeletal muscle and weakness, often accompanied by skin inflammation. Onset of this disease usually occurs between 40 and 50 years of age. Women are affected twice as commonly as men are. The cause is unknown.

How is it diagnosed?

History: Muscle weakness is the primary complaint, usually noted first in the legs. Individuals often complain of inability to climb stairs and inability to raise their arms above their heads and difficulty swallowing or breathing. Symptoms can develop gradually or suddenly. Muscle pain is often reported if onset is sudden. Symptoms may have occurred after an illness with fever or rash, or a mild injury.

Physical exam: Weakness is noted in the neck muscles (particularly at the front of the neck), thighs, and shoulders. The muscles are occasionally tender and swollen.

The disease typically causes a scaly red rash of skin on the face, knuckles, elbows, knees or ankles. The fingers and nails may be warm and red. Swelling around the eye can be seen, along with a purplish discoloration of the eyelids.

Tests: Blood tests of muscle enzymes (creatine phosphokinase and aldolase, and LDH) will be elevated. Electromyography is also used, and reveals a pattern suggestive of the disease.

Removal of a sample of an affected muscle (biopsy), usually the quadriceps or deltoid, is needed for a definitive diagnosis. Microscopic exam of the muscle shows a characteristic kind of inflammation.

How is dermatomyositis treated?

The initial treatment for dermatomyositis is corticosteroids. If there is no response to steroid treatment, other drugs to suppress the immune response are added.

Medications

Information	Brand	Generic	Label	Rating
	Deltasone	Prednisone
	Imuran	Azathioprine
	Prograf	Tacrolimus
	Rheumatrex	Methotrexate

What might complicate it?

Individuals with dermatomyositis have an increased risk of developing a cancer. The malignancy may be present along with the initial symptoms or may not develop until later. The steroids used to suppress the disease and improve the weakness can cause muscle weakness if given in too high a dose, so the steroid dose requires careful adjustment.

Predicted outcome

For those individuals who respond to therapy, expected outcome is decreased severity or disappearance of symptoms (remission). The disease is disabling for individuals who do not respond.

Alternatives

Similar disorders causing muscle weakness are scleroderma, lupus, and rheumatoid arthritis. Other disease possibilities are hyper and hypothyroidism, chronic inflammatory polyneuropathy, multiple sclerosis, myasthenia gravis, Eaton-Lambert disease, and amyotrophic lateral sclerosis. Many drugs and alcohol can also produce muscle weakness. The rash of dermatomyositis can be similar to lupus, psoriasis, lichen planus, and mycosis fungoides.

Appropriate specialists

Rheumatologist, oncologist (if cancer is present), neurologist, physiatrist, and dermatologist.

Last updated 6 October 2011