What is Dermatomyositis?

Simply Put

Dermatomyositis (DM) is classified both as a neuromuscular disease and an autoimmune disease. It is thought that the inflammation resulting in cell damage is created when the immune system attacks healthy muscle tissue and blood vessels under the skin.

DM is one of several diseases in the Idiopathic Inflammatory or Acquired Myopathy category. The term “idiopathic” means no known cause, however some cases are known to have been caused by medications, viruses, bacteria, trauma, toxins, cancer or other illness.

Muscles typically affected by PM/DM
Muscles typically affected by PM/DM. Image courtesy of the Muscular Dystrophy Association.

It is called an “acquired” myopathy because it is not an inherited disorder. However it is thought that people with DM may have a genetic predisposition and some factor, such as the ones mentioned above, triggers the immune system, which goes haywire and attacks healthy cells.

Characteristic of Dermatomyositis

There can be significant variation in symptoms from patient to patient. Not everyone diagnosed with Dermatomyositis will display all the symptoms, and the intensity of the symptoms can vary widely.

Muscle Involvement

Muscle weakness can develop over a period of days, weeks or months, is typically symmetrical (both sides of the body) and affects proximal muscles (muscles which are closest to the body’s core), such as the quadriceps, hip flexors, neck, shoulder and deltoid muscles.   This weakness often leads to difficulty climbing stairs, rising from a chair or the floor, turning in bed, lifting, styling hair or reaching over the head for something like an item on a shelf. Muscle weakness may be accompanied by pain (myalgia).

Dermatomyositis is considered a chronic disease with no known cure, however, many people respond well to certain treatments or combination of treatments with improvement in symptoms or complete remission of symptoms. As discussed in detail in the Treating Myositis section, finding the most effective treatment for your specific symptoms can be a challenge.

Some patients, although not common, experience weakness in distal muscles, those farthest away from the body’s core such as hands and fingers.

Dermatomyositis is considered a rare disease. Approximately 5 to 10 people per million are diagnosed in the US with a form of Myositis each year.

Skin Involvement

The second manifestation of DM, and the reason the term “dermato” is used, is skin involvement, which frequently develops before the muscle weakness. DM is considered to be the easiest form of Myositis to diagnose due to the characteristic “heliotrope” rashes. Heliotrope refers to the pink-purple-violet shade of the heliotrope flower.

The rashes often appear on the eyelids and the face, as well as around the knuckles, nails, knees, elbows, back and chest region, which is referred to as the “shawl” rash. The rash has a tendency to be blotchy with blue-purple stains and, in many cases, is the first symptom of Dermatomyositis. Some may be painful, itchy, and intense enough to disturb sleep.

Amyopathic Dermatomyositis (ADM)

There is a subset of DM which has skin manifestations only with no muscle involvement, this is called Amyopathic Dermatomyositis (ADM), or Dermatomyositis Sine Myositis. About half of those diagnosed with ADM suffer from fatigue. Other significant potential complication of ADM is a higher risk for cancers, particularly internal malignancies and rapidly-progressing lung disease.

MSU Observation: Doctors advise people who have dermatomyositis to avoid exposure to direct sunlight, which is the most common trigger of skin symptoms. Wearing sun and UPF protection, including topicals, clothing, hats and gloves is recommended. Some people with Dermatomyositis are so photosensitive, that they need to protect themselves from windows and commercial lighting, such as fluorescents. It may be necessary to have car windows tinted, and permission is frequently granted with documented photosensitivity for a darker window tint than what is legal in their state or municipality.

When Dermatomyositis is suspected, physicians will also request lab work for certain tests such as the Myositis Specific Antibodies (MSA), Antinuclear Antibodies (ANA) and Myositis Associated Antibodies (MAA) panels. If the patient tests positive to certain antibodies, the results may offer physicians the best chance of treating the disease successfully as well as offering “predictors” of possible disease progression and complications.

Signs and Symptoms of Dermatomyositis

  • Skin rashes and discolorations which affect sun-exposed areas, cheeks, nose, shoulders, upper chest, and elbows.
  • Proximal muscle weakness (muscles closest to the trunk, such as shoulders, thighs, and hips)
  • Symmetrical muscle weakness (the same muscles on both sides of the body)
  • Muscle pain (Myalgia)
  • Joint inflammation
  • Ragged cuticles, prominent blood vessels on the nail folds, and other nail-bed abnormalities
  • Dry, scaly, or rough skin
  • Fatigue (may be life-altering and disturbs sleep patterns)
  • Weight loss
  • Low-grade fever
  • Lung problems such as Interstitial Lung Disease (ILD), Pulmonary Fibrosis, or Labored breathing (Dyspnea)
  • Difficulty swallowing (Dysphagia)
  • Vocal changes which can produce a hoarse or changing voice (Dysphonia)
  • Inflammation of the fat which can feel like little bumps lying just under the skin and can be tender to the touch (Panniculitis)
  • Irregular heartbeat (Arrhythmia)
  • Changes in the scalp resembling psoriasis and hair loss
  • Gastrointestinal ulcers and intestinal perforations, also more common in children

Complications of Dermatomyositis

  • Calcinosis (hard, often painful lumps or sheets of calcium that form under the skin’s surface)
  • Increased risk of falls
  • Gottron’s papules or Gottron’s sign (bumps found over the knuckles, elbows and knees, often with a raised, scaly break-out)
  • Increased risk of infection
  • Other connective tissue diseases (overlaps)
  • Interstitial lung disease (ILD)
  • Inflammation of the myocardium or inflammatory cardiomyopathy
  • Raynaud’s phenomenon
  • Cardiovascular disease
  • Gottron’s papules or Gottron’s sign (bumps found over the knuckles, elbows and knees, often with a raised, scaly break-out)
  • Aspiration pneumonia
  • Complications and side effects related to Myositis treatments
  • Increased risk of having certain types of cancer

Dermatomyositis in images

Classic Heliotrope rash shown over eyelids
Classic Heliotrope rash
DM "Shawl Sign" rash
DM "Shawl Sign" rash
Gottron’s papules or Gottron’s Sign
Gottron’s papules or Gottron’s Sign
Calcinoisis
Calcinoisis

MSU Observation: Overlap Syndrome, having more than one autoimmune disease, is somewhat common in patients with Dermatomyositis and Polymyositis. These can include Lupus, Scleroderma, Raynaud’s phenomenon, and Sjögren’s syndrome.

Dermatomyositis and Cancer

Cancer can be an underlying cause of Dermatomyositis and may precede its onset. If the cancer precipitated DM, removal of the cancer may result in remission of the Dermatomyositis.

Dermatomyositis in adults has also been linked to an increased likelihood of developing cancer post diagnosis, particularly cancers of the cervix, lungs, pancreas, colorectal system, breasts, ovaries and gastrointestinal tract and non-Hodgkin’s lymphoma.   The risk of cancer appears to level off about three years after a diagnosis of DM. The incidence of cancer is higher in Dermatomyositis than in Polymyositis, and particularly in those with certain antibodies. It is strongly suggested that appropriate cancer screenings be conducted upon diagnosis and in the years after a Myositis diagnosis.

Because of a high cancer risk, both before and after diagnosis, doctors will often perform cancer screenings at the onset or suspicion of Dermatomyositis. Cancer will continue to be a risk with such patients, and cancer screening should be continued on a regular basis and more often than suggested for the patient’s age group per doctor’s advice, particularly because of the increased cancer risk of immune-suppressing treatments.

Dermatomyositis vs. Normal muscle biopsy

Muscle biopsy comparison of normal muscle tissue versus muscle tissues affected with Dermatomyositis.

Image courtesy of

The Muscular Dystrophy Association

Simply Put

“Simply Put” is a service of Myositis Support and Understanding, to provide overviews of Myositis-related medical and scientific information in understandable language.

MSU volunteers, who have no medical background, read and analyze often-complicated medical information and present it in more simplified terms so that readers have a starting point for further investigation and consultation with healthcare providers. The information provided is not meant to be medical advice of any type.

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Hi, this may be interesting to you: Dermatomyositis (DM)! The link is included below: https://understandingmyositis.org/myositis/dermatomyositis/ --- Myositis Support and Understanding is a 501(c)3 nonprofit organization.