A blotchy rash can be a symptom of a huge range of health issues. While a rash is far more likely to be, say, an allergic reaction to something in your environment, it can also can be one of the early signs of dermatomyositis (DM), one of five types of myositis, a rare autoimmune disorder that causes inflammation in the muscles and weakens them.

Like so many autoimmune disorders, dermatomyositis most often affects women, typically between the ages of 30 to 60, says Rohit Aggarwal, MD, a rheumatologist and an associate professor in at the University of Pittsburgh School of Medicine as well as the chair of the medical advisory board for the Myositis Association. Though experts don’t know why, dermatomyositis tends to be more common in African American women. The condition can also affect children, usually between the ages of 5 and 15. Overall, there are about 30,000 to 50,000 Americans living with dermatomysositis, according to Dr. Aggarwal.

While there’s no cure for this condition, it can be successfully managed with a combination of medications. Getting an accurate diagnosis is key.

Symptoms of Dermatomyositis

A patchy rash is usually what first sends people to their doctor’s office. And with good reason — the rash can be itchy and painful. This dark red or purplish rash usually appears in a V-shaped pattern on your chest or in a shawl-like pattern across your shoulders and neck, says Linda Kobert, RN, MSN, research and communications director of the Myositis Association in Alexandria, Virginia. The rash can also crop up on eyelids, cheeks, knuckles, elbows, and, sometimes, the knees.

Because of the color — a dark red or purple — it may be harder to spot if you’re African-American or have a darker complexion, she adds. But you may have other symptoms that can tip a doctor off to dermatomyositis, including fatigue and hard lumps of calcium under the skin (known as calcinosis, though this is more common in kids than in adults).

Many people with DM go on to develop muscle weakness, especially in the muscles nearest to the trunk of their bodies (called proximal muscles). You may begin to feel that your neck, back, hip, and shoulder muscles are getting weaker — making it tough to get off the floor or a chair, or wash your hair.

There is a form of dermatomyositis called amyopathic DM that doesn’t involve muscle weakness at all. Those patients have the rash, and they may have a slight muscle weakness that even sometimes they don’t recognize, says Kobert. However, their muscles may show signs of inflammation if the muscle tissues are biopsied, even if they don’t have symptoms that affect daily function or quality of life.

Causes of Dermatomyositis

No one knows for sure what causes DM. Researchers think that people with DM may have a genetic predisposition for autoimmune disorders. In families, one member can go on to develop, say, multiple sclerosis while another could develop DM.

Geography may play a role too. For about 20 percent of people with DM, the sun will exacerbate symptoms, so people with DM need to be especially careful when they’re out and about.

“In countries or the regions where there’s more ultraviolet radiation and high sun exposure, there are higher incidents of dermatomyositis,” says Dr. Aggarwal. But this is a loose association, he cautions. And you need to have the genetic predisposition in the first place.

Dermatomyositis vs. Similar Conditions

DM can sometimes be misdiagnosed as lupus, as the rash can sometimes present in the same places as the butterfly-shaped rash that is a telltale symptom of lupus — on the face as well as on the back and shoulders. Even more problematical, when doctors perform a skin biopsy, the two conditions often look the same.

Lupus and dermatomyositis also have other symptoms in common. Patients can experience flare-ups in the sun, have chronic fatigue, and often experience muscular pain.

As well, people can have both diseases at the same time, which may make diagnosis harder. But a savvy dermatologist or rheumatologist can distinguish the conditions with a series of diagnostic tests.

How Dermatomyositis Is Diagnosed

“The DM rash is classic and rather specific,” says Dr. Aggarwal. When the dark color rash appears on the knuckles and hands, it’s known as Gottron’s papules; on the eyelids, it’s called a heliotrope rash. “They are so specific, if you have them, that’s dermatomyositis, generally speaking. A good dermatologist or rheumatologist should be able to recognize it.”

But just to be sure, doctors will perform a skin biopsy, and then do a thorough physical exam to check for muscle weakness in the muscles closest to the trunk of your body. Your health provider will also order a blood test to check whether a muscle enzyme called creatine kinase (CK) is elevated. People with dermatomyositis usually have very high levels of CK, says Kobert. A blood test will also reveal any autoantibodies, or abnormal proteins that signal an autoimmune disorder.

Up to 70 percent of patients may have one of the 15 to 17 myositis-specific autoantibodies. These autoantibodies may also help determine your odds of developing cancer, which is often a higher-than-average risk for people with DM. Those cancers include colorectal, breast, ovarian, pancreatic, and non-Hodgkin’s lymphoma.

Other diagnostic tests, like an electromyogram (EMG) and nerve conduction velocity (NCV) can distinguish muscle problems (called myopathies) from neurological conditions, like myasthenia gravis, Dr. Aggarwal explains. Sometimes MRI is used to spot muscle inflammation or damage, which can then help the doctor to decide which muscles to biopsy.

“The biopsy can reveal inflammation around the bundles of muscle fibers, which is a sign of dermatomyositis,” he explains. If you test positive in three or four of these tests, then that generally leads to a dermatomyositis diagnosis, he adds.

How Dermatomyositis Is Treated

Because the disease presents differently in patients, there’s no one-size-fits-all treatment plan. But typically a first-line treatment will include steroids, like prednisone, to slow the effects of inflammation. One drug that’s frequently used on DM patients is acthar, an injection that stimulates the body to produce hormones that can reduce inflammation.

Patients with DM have to take high doses of steroids for at least six months to a year, and that can lead to significant side effects, including bone and muscle-mass loss, diabetes, and mood changes, says Dr. Aggarwal. “That’s why we try to limit steroids as much as we can.”

To counter the effects of long-term steroid use, doctors also rely on such immunosuppressant drugs as methotrexate or azathioprine — either given in conjunction with the steroids or by themselves — that can inhibit the immune system to prevent or minimize flare-ups. If those immunosuppressant drugs fail, there are others, such as mycophenolate, that may help.

One drug that has been highly effective in treating dermatomyositis is intravenous immune globulin (IVIg), which is comprised of large amounts of donated blood plasma. “We could use IVIg at any stage of the disease, because IVIg can be combined with any immunosuppressive drugs that doctors give. So we use the IVIg as a sort of bridge or at least to get the patient better. Sometimes we have to use IVIg as the main therapy,” says Dr. Aggarwal. It is very expensive, though, and because it hasn’t been approved by the FDA to treat dermatomyositis (or any other form of myositis), many insurance companies won’t cover it.

Lifestyle Changes for Dermatomyositis


With exercise, the key is to find something you like, be it swimming, tai chi, or walking, and try to do it every day to strengthen your muscles, says Kobert. Just don’t push yourself to the point of exhaustion.


While exercise can help people with all forms of myositis, the role of diet isn’t as clear. “Diet and other kinds of non-medical interventions have not been studied in myositis,” says Kobert, mostly because the disease is so rare. “What we usually recommend is that people adopt a healthy anti-inflammatory diet.” This includes eating more fruits and vegetables, lean protein, nuts and legumes, unsaturated fats, and whole grains — and eating fewer highly processed foods, sugar, and red meat.

Sun Protection

It’s very important for patients with DM to protect themselves from direct sunlight, as that can make symptoms worse. So always use sunscreen (at least SPF 50) all year long and don a hat and sunglasses when outdoors. Wear long sleeves, pants, or long skirts and dresses to minimize skin exposure to the sun. Consider investing in special sun-protective clothing.

The goal of dermatomyositis treatment is to get patients to a point where their condition can be controlled with medication so the rash and muscle weakness is minimal, explains Dr. Aggarwal. And the good news is that patients who do get better are able to go back to about 90 percent of their baseline, he says.

“However, we need better treatments. About a third of cases are difficult to treat and another third have significant side effects in order to achieve good level of improvement.”

When your medications don’t work or are causing you serious side-effects, there’s a possibility you are eligible to join a clinical trial. You can find information about ongoing trials at the Myositis Association.

Keep Reading

  • Was This Helpful?