Amyopathic dermatomyositis (ADM) is a subtype of dermatomyositis that involves skin symptoms without the associated muscle symptoms. Dermatomyositis is a rare condition characterized by a skin rash alongside muscle weakness.

ADM is also known as dermatomyositis sine myositis. It can also be classed alongside hypomyopathic dermatomyositis (HDM) as a type of clinical amyopathic dermatomyositis (CADM).

Read on to learn more about the symptoms of ADM. This article also looks at causes, diagnosis, treatment options, and more.

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ADM can cause a person to develop a variety of different symptoms.

Visible symptoms on the skin can include:

  • heliotrope rash, which is purple discoloration of the eyelids that also involves swelling
  • pink rash on the face, neck, forearms, and upper chest
  • facial redness and swelling
  • skin ulcers
  • Gottron papules, which are red or purple bumps that occur on the knuckles or back of the hand
  • Gottron sign, which is a flat red rash that occurs on the knees, fingers, elbows, or ankles
  • periungual telangiectasia, which are dilated blood vessels that occur on the skin at the base of the fingernail
  • hyperpigmentation plaques, which are thickened areas of darkened skin
  • scalp inflammation

Other symptoms can include:

  • fatigue
  • itching
  • sensitivity to light
  • hair thinning
  • Raynaud syndrome, a condition that causes decreased blood flow to the fingers
  • calcinosis, which is the development of calcium deposits in the soft tissues

There is little information regarding the specific causes of ADM. The cause of dermatomyositis in general is currently unclear. However, researchers believe that it may develop as a result of immune, genetic, and environmental factors.

The charity Myositis Support and Understanding lists ADM as an autoimmune disease. Autoimmune diseases occur when a person’s immune system mistakenly attacks healthy cells.

A 2019 study found that there were clusters of CADM cases in areas of Pennsylvania that had high pollution levels. This may indicate that exposure to pollution could be a trigger for CADM. Further research is necessary to confirm these effects.

ADM can be difficult for a doctor to correctly diagnose. It can have similar symptoms to other conditions. A 2019 review noted that ADM had been misdiagnosed as:

  • undifferentiated connective tissue disease (UCTD), an autoimmune disease that affects connective tissue
  • mixed connective tissue disease (MCTD), an autoimmune condition that features symptoms of multiple disorders
  • dermatitis, which is inflammation of the skin
  • rosacea, a skin condition that causes reddening of the face
  • psoriasis, an autoimmune condition that causes itchy, scaly plaques of skin

Information from the 2019 review states that the European League Against Rheumatism and American College of Rheumatology method for diagnosing ADM requires a doctor to check a person for Gottron papules, Gottron sign, and heliotrope rash.

If a person has two out of three of these symptoms alongside no muscular symptoms, a doctor may diagnose ADM. They may also diagnose the condition if a person has one of the main criteria and two minor criteria, such as itching and calcinosis.

During the diagnosis of ADM, a doctor may ask a person about their symptoms and medical history. After examining a person’s skin, a doctor may perform certain blood tests. The presence of anti-melanoma differentiation-associated protein 5 (MDA5) antibodies in a person’s blood may indicate that they have ADM.

A doctor may also test the levels of muscle enzymes in a person’s blood. Elevated levels of these enzymes may indicate that muscle fibers have been damaged. This would mean that a person had dermatomyositis rather than ADM.

The National Organization for Rare Disorders states that a doctor may use the following to treat a person with ADM:

  • topical corticosteroids, which are creams that can help reduce inflammation
  • certain antimalarial drugs
  • immunosuppressants, such as methotrexate and mycophenolate mofetil
  • intravenous (IV) immunoglobulin, which uses antibodies to suppress harmful ADM antibodies

They may also recommend that the individual applies plenty of sunscreen and avoids spending time in the sun where possible.

ADM can cause a person to develop a number of serious complications. This means it is important for a person to receive a prompt diagnosis from their doctor.

A 2018 study found that more than 25% of people who have ADM go on to develop cancer. A 2020 case study noted that dermatomyositis is often associated with the development of breast cancer.

ADM may also increase a person’s risk of developing interstitial lung disease (ILD). ILD is a group of conditions that can cause a person to develop scarring or inflammation in their lungs. It can cause symptoms such as:

Damage to the lungs due to ILD can be irreversible, and it can worsen over time. If a person does not receive treatment for severe cases of ILD, they may develop life threatening complications such as heart failure or respiratory failure.

Dermatomyositis is a rare condition that affects approximately 9.63 in 1 million people. ADM accounts for less than 20% of cases of dermatomyositis.

A 2017 case study noted that ADM generally develops in early adulthood and is more likely to affect people assigned female at birth.

There is currently no cure for dermatomyositis or other forms of myositis.

However, treatments for ADM may help a person to manage their symptoms.

Amyopathic dermatomyositis (ADM) is a rare condition. It can cause various skin symptoms, such as Gottron papules, Gottron sign, and heliotrope rash.

Without prompt treatment, ADM can cause a person to develop certain potentially serious complications. Treatments that may help include corticosteroids, immunosuppressants, antimalarial drugs, and IV immunoglobulin.

A person should contact their doctor as soon as possible if they develop any signs of ADM.