What Is Amyopathic Dermatomyositis (ADM)?

Amyopathic dermatomyositis (ADM), also called dermatomyositis sine myositis, is a subtype of dermatomyositis characterized by typical skin manifestations without clinically significant muscle weakness. ADM is a rare cutaneous form of dermatomyositis in which characteristic skin findings are present for at least 6 months without clinically apparent muscle weakness.  Clinically amyopathic dermatomyositis (CADM) includes both amyopathic dermatomyositis (ADM) and hypomyopathic dermatomyositis (HDM).

Hypomyopathic dermatomyositis accounts for less than 5% of all diagnoses of dermatomyositis. It can be indicated with minor muscle abnormalities or damage. More importantly, HDM is associated with interstitial lung disease (ILD) and may carry a more unfavorable prognosis than amyopathic dermatomyositis with ILD. In severe cases, interstitial lung disease may cause fatal complications in CADM patients. 

Amyopathic means lack of muscle weakness or no muscle damage. The term dermatomyositis is defined as a rare inflammatory disease that displays muscle weakness and a hallmark symptom of skin rash. 

As previously mentioned, ADM is a rare condition, and it affects fewer than 200,000 people per year. ADM occurs more frequently in women than men and has been reported more commonly in Caucasian and Asian populations.  ADM most commonly presents between 40 and 60 years of age.

Amyopathic Dermatomyositis Signs and Symptoms

Amyopathic dermatomyositis symptoms may vary from patient to patient. Symptoms vary among patients, and disease severity can range from mild cutaneous findings to systemic complications.   

The symptoms patients can experience with amyopathic dermatomyositis include the following:

• Eyelid abnormality
• Photosensitive skin rashes, commonly affecting the face, shoulders, upper chest, elbows, and hands
• Muscle aches
• Weight loss
• Low-grade fever
• Fatigue that may interfere with daily activities
• Joint inflammation
• Gottron’s papules or Gottron’s sign, which are raised, scale-like bumps that are seen over the knuckle, elbow, and knee areas
• Lung inflammation
• Swelling around eyes

Causes of Amyopathic Dermatomyositis 

The exact cause of amyopathic dermatomyositis remains unknown. ADM is believed to involve autoimmune mechanisms that may affect the skin, lungs, and other organs.

Amyopathic Dermatomyositis Diagnosis

Diagnosis is based on characteristic skin findings of dermatomyositis present for at least 6 months without clinically significant muscle weakness. The following amyopathic dermatomyositis diagnostic criteria and tests may be used to help aid with the diagnostic process:

• Typical dermatomyositis skin symptoms are present (i.e., red skin patches over the knuckles and Gottron papules [red bumps on the skin or erythematous eruptions], periorbital swelling, purple rash, etc.).
• Skin biopsy demonstrates diminished or reduced density of blood capillaries and deposits of membrane attack complex on tiny blood vessels.
• Muscle biopsy may help to reveal muscle inflammation and other problems (i.e., muscle disease, damage, or infection). 
• Muscle enzyme levels, including creatine kinase (CK), are often normal in patients without muscle involvement.
• Pulmonary function tests are ordered to assess dermatomyositis-associated conditions, especially in those with lung inflammation. 
• Electromyography (EMG) findings are typically normal in clinically amyopathic dermatomyositis.

Amyopathic Dermatomyositis Treatment

Although there is currently no cure for amyopathic dermatomyositis, treatment focuses on symptom management, prevention of complications, and improving quality of life.  Listed below are some of the treatment options available for patients to help with symptoms and improve their overall quality of life:

• Sun protection:
  Wear photoprotective clothing, apply ample sunscreen, and avoid the sun as much as possible. 
• Corticosteroid topical therapy:  
  This therapy is applied over damaged skin to treat dermatomyositis symptoms. Long-term corticosteroid use may increase the risk of adverse effects and should be monitored by a healthcare provider. Your health care provider may decrease the dose once the symptoms start improving.
• Immunosuppressive agents:
  Agents such as mycophenolate mofetil, azathioprine, and methotrexate may be beneficial to help manage dermatomyositis symptoms. Mycophenolate mofetil is mainly used for treatment if lung impairment is involved.
• Rituximab:
  Rituximab may be considered in refractory or treatment-resistant cases.
• Physical therapy:
  Physical therapy may help to increase and maintain your strength and flexibility with routine exercise. This may help in restoring your health over time.
• Surgery:
  Surgery is an option to get rid of painful calcium deposits in the joints. Thus, surgery protects such patients from recurring skin infections and other diseases.
• Intravenous immunoglobulins (IVIG) therapy:
  Immunoglobulin is obtained from the blood plasma of many blood donors. It contains healthy antibodies that suppress or block the harmful dermatomyositis antibodies that cause skin and muscle damage. Intravenous immunoglobulin (IVIG) therapy may be effective in some patients, although repeated treatments can be costly. It may require repeated infusions on a regular basis to continue the positive effects of treatment.

Living With Amyopathic Dermatomyositis

Living with ADM can significantly affect the daily lives of patients and their families. Many patients who have developed amyopathic dermatomyositis may need life-long treatments to manage their condition. Below are tips to help live a balanced life and several coping strategies: 

• Educate yourself about the disease and work closely with your doctor to manage and control your illness.
• Keep your doctor or health care professional updated about new cutaneous signs and other related symptoms you may develop. 
• Remain physically active as tolerated and follow an exercise plan recommended by your healthcare provider or physical therapist.
• Balance activity with adequate rest to help manage fatigue.
• Acknowledge your emotions (frustration, denial, anger, fear of isolation, etc.). Stay close to your loved ones for support, and manage your daily routine. 

Complications of Amyopathic Dermatomyositis

Some patients with ADM may have an increased risk of malignancy, making age-appropriate cancer screening important. Certain malignancies, including ovarian and nasopharyngeal cancers, have been associated with dermatomyositis in some studies. Therefore, cancer screenings are critical for these patients before, during, and after diagnosis.

Similar to the symptoms of ADM,  other complications may include:

• Lung disease (interstitial lung disease, aspiration pneumonia, breathing problems, etc.)
• Heart disease (inflammation of the heart muscle)
• Weight loss
• Malnutrition
• Calcium deposits in the joints

These complications can be debilitating and can worsen the disease prognosis, making treatment options more difficult and complex in certain cases.

FAQs

What is  Clinically  Amyopathic  Dermatomyositis (CADM)?

Clinically amyopathic dermatomyositis (CADM) is a rare disease with unknown origin. It is characterized by the specific cutaneous lesions of dermatomyositis without clinical features or laboratory findings of myopathy or muscle weakness. Clinically amyopathic dermatomyositis is estimated to account for approximately 20% of dermatomyositis cases.

Is  Amyopathic  Dermatomyositis an autoimmune disease?

Amyopathic dermatomyositis has significant resemblances to autoimmune diseases. It involves the skin as well as other organs. The condition is believed to involve immune system dysfunction, although the exact cause remains unclear.