What is dermatomyositis?

Dermatomyositis (dermato = skin; myositis = muscle) is an autoimmune condition that characteristically causes a skin rash and muscle weakness.  Autoimmune diseases occur when the body’s immune system (which normally protects you from infections and cancer) begins to act abnormally and mistakenly attacks normally-functioning parts of your body, leading to inflammation of various body tissues and internal organs.  In dermatomyositis, this typically causes weakness of the proximal muscles of the body (such as the hips, thighs, shoulders, upper arms, and neck).  Some patients with dermatomyositis will note that it is hard to get out of a chair or comb their hair due to the weakness.  A variety of skin rashes can occur with dermatomyositis, some of which can be intensely itchy and scaly and others which can cause the skin to be open and ulcerated (i.e. non-healing sores).  The rashes can be localized to areas of the body or can involve a large area of the patient’s body.  Usually the rash is prominent in the sun-exposed areas of the body (such as the face, hands, arms, chest, neck, and upper back).  Some of the most typical changes involve a red rash with a purple hue that involves the knuckles, tops of hands, elbows, knees, upper chest, face (including the eyelids), neck, upper arms, and back of the shoulders.  Sometimes the skin around the fingernails may appear rough and have small blood vessels visible underneath the skin.  Other patients may note dryness and cracking of the fingers reminiscent of a person who does a lot of manual labor with their hands (known as “mechanic’s hands”).  Some people with dermatomyositis experience prominent redness and scaling of their scalp that is associated with intense itching.  Rarely, patients with dermatomyositis (particularly children) may develop hard white-yellow nodular calcium deposits of the skin and underlying structures (including the muscle), which can cause significant pain, ulceration of the skin, and limitation in movement of the joints.

Although dermatomyositis usually involves both the skin and muscle in affected patients, some people may only experience involvement of the skin without ever developing muscle weakness over many years, a condition termed “amyopathic” (without muscle) dermatomyositis.  A recent population-based study in southern Minnesota estimated that approximately 20% of people who develop dermatomyositis may only have skin involvement (without ever developing muscle weakness).

What caused my dermatomyositis?

The exact cause of dermatomyositis is unknown.  Dermatomyositis occurs when your immune system mistakenly starts attacking your own body’s cells and organs (known as “autoimmunity”).  It appears that patients who are at risk for developing dermatomyositis possess a certain combination of genes that may make them more likely to develop the condition if they are exposed to certain environmental triggers such as infection (a variety of viruses have been suggested to possibly play a role) or ultraviolet radiation from the sun.  The environmental triggers then cause the patient’s body to develop an abnormal immune response directed against the patient’s own body (“autoimmunity”), which subsequently leads to the tissue damage that occurs in patients with dermatomyositis.  In rare situations, medications have been associated with the development of dermatomyositis (examples include hydroxyurea, cholesterol-lowering medications [statins], and anti-tumor necrosis factor-alpha [TNF-α] medications).

What other complications am I at risk for?

In addition to skin rashes and muscle weakness, people with dermatomyositis may experience the following complications and disease associations:

• Cancer – approximately 20-25% of patients may have an associated cancer which can occur before, after, or at the same time as the dermatomyositis. A variety of cancers can be associated with dermatomyositis including those of the lung, ovaries, breast, and colon.  All adult patients with dermatomyositis (including those with disease limited to the skin [amyopathic]) need to evaluated for the possibility of cancer (see below).

• Interstitial lung disease – dermatomyositis can affect the lungs and cause symptoms such as shortness of breath or a dry cough. Sometimes the lungs can be affected even without patients having any noticeable symptoms, and in some patients the lung may become involved months to years after they initially developed the disease.  All patients with dermatomyositis need to have special tests of their lungs when they are initially diagnosed as well as annually thereafter (see below).

• Swallowing difficulties – known as dysphagia, this can occur when dermatomyositis affects the esophagus.

• Arthritis – patients with dermatomyositis may experience joint pains and joint swelling associated with their condition

• Heart abnormalities – rarely dermatomyositis can affect the heart muscle and therefore lead to complications such as conduction defects of the heart or an enlarged heart (cardiomyopathy).

What to expect from my dermatomyositis?

Each patient with dermatomyositis is different; and therefore the severity of disease, associated complications, recommended treatments, and long-term outcomes will be different for each person and will need to be individualized by your doctors.

When someone develops symptoms and skin rash findings that are suggestive of dermatomyositis, it is important to confirm the diagnosis and to assess what parts of the body are affected by the condition.  Your doctor will likely perform a variety of tests to assess for dermatomyositis which may include some or all of the following:

• Skin biopsy – this will help show typical changes of dermatomyositis or rule out other skin conditions that can have similar skin findings
• Blood tests to evaluate for muscle weakness, associated autoimmune conditions, and cancer
• More detailed testing of the muscles if indicated based upon your symptoms or blood test findings – electromyogram (EMG), magnetic resonance imaging (MRI), or muscle biopsy
• Lung function tests (i.e., pulmonary function tests [PFT’s]) – these can help your doctor determine if dermatomyositis could be affecting your lungs. If these are abnormal or if you have breathing difficulties, your doctor may order a CT scan of your chest and have you visit with a pulmonologist (lung doctor).  It is recommended that patients with dermatomyositis undergo lung function tests every year to ensure that they do not develop involvement of their lungs that may not be detectable based on breathing symptoms alone.
• Cancer screening tests – generally this involves a thorough history, physical exam, and blood tests with a general internist. Age-appropriate cancer screening tests such as mammogram, Pap smear, and colonoscopy may be recommended.  A pelvic ultrasound in women to assess for ovarian cancer is also recommended.  Sometimes the initial cancer screening may also involve a full-body radiographic examination such as a PET scan or a CT scan of the chest, abdomen, and pelvis.  In general, the highest risk for cancer is within the first 3 years after diagnosis of dermatomyositis, and therefore patients should be seen at least annually (and sooner if symptoms indicate) by a general internist to assess for this possibility.

It is unknown how long dermatomyositis will last in a particular person.  Some people may only have significant symptoms for months to a few years, while others may have experience ongoing involvement over many years.  In some patients with both skin and muscle involvement, medications may adequately control the muscle inflammation but not adequately treat the skin inflammation.  This type of skin involvement can be particularly difficult to control.

What can I do to make my skin better?

The treatment of dermatomyositis varies among individuals and is determined by several factors including how severely the skin is affected as well as whether there is other organ involvement.  If a patient has both skin involvement and significant muscle inflammation, he or she is generally cared for jointly by a dermatologist and rheumatologist and typically will receive prednisone in combination with another medication that suppresses the immune system (immunosuppressive or “steroid-sparing” medication) such as methotrexate, mycophenolate mofetil, or azathioprine.  The prednisone may need to be continued and gradually tapered over many months to even a couple of years.  Some patients that have both skin and muscle involvement of their dermatomyositis may need other medications such as intravenous immunoglobulin (IVIg) or rituximab.

If a person has dermatomyositis that is limited to the skin, then the treatment options are similar although usually not as aggressive as the treatments noted above unless there is severe skin disease present.  Prednisone is usually avoided for skin-limited (amyopathic) dermatomyositis other than for selected circumstances that require a brief (2-3 month) course of prednisone while waiting for another medication to reach therapeutic blood levels.  In general, it takes at least 3 months of using a particular medication at its full dose to determine if it will be effective for treatment of your dermatomyositis.  Some treatment options for the skin rashes of dermatomyositis that your dermatologist may discuss with you include:

• Sun protective measures including daily sunscreen, sun-protective clothing, and sun avoidance strategies (see below)
• Topical steroid creams and ointments (e.g., triamcinolone 0.1% cream)
• Topical calcineurin inhibitors (e.g., tacrolimus 0.1% ointment)
• Antimalarial medications (e.g., hydroxychloroquine)
• Immune-suppressing medications (e.g., methotrexate, mycophenolate mofetil, azathioprine)
• IVIg – this can be effective for severe skin disease that does not respond to more standard treatments noted above, and can be used in patients that have an associated cancer or infection (as this medication does not suppress your immune system)

How do I stop the itch?

Dermatomyositis can cause significant itching of the skin in some patients.  Treatment may consist of a combination of topically-applied creams or ointments as well as pills that need to be taken by mouth in order to help ease the itching.  Over-the-counter options include a lotion that contains a combination of menthol and camphor (e.g., Sarna).  Antihistamines (“anti-itch” pills) such as diphenhydramine (Benadryl) and some prescription antihistamines can also be taken during the day and at bedtime if the itching is severe.  Routine use of a moisturizer in order to keep the skin well-hydrated is also important, as dryness of the skin can worsen the itching associated with dermatomyositis.  The treatments listed above are also important to control the inflammation, which will eventually stop the itching.

Is my family at risk?

Dermatomyositis is not contagious and rarely runs in families.  However, if you have dermatomyositis, your family may have a slightly higher risk of developing autoimmune diseases.

Other resources

Mayo Clinic Dermatomyositis Patient Information

Sontheimer RD. What patients and their families often want to know. Dermatology Online Journal. 8(1);2002:6.

Sontheimer RD. Clinically amyopathic dermatomyositis: What can we now tell our patients? Archives of Dermatology. 146(1);2010:76-80.