What’s the Dx? Hint: no muscle weakness...

May 18, 2016

Errol Ozdalga, MD; @eozdalga
Clinical Assistant Professor, Stanford School of Medicine

37 yr old male with a history of these lesions on his the back of his hands for the past two years. Notes no other medical issues. No weakness, fatigue, fevers or rashes anywhere else on his body. He works as a chiropractor and is concerned about his patients seeing his hands. Use of various over the counter treatments such as topical steroids and moisturizers did not improve the lesions.

What is amyopathic dermatomyositis?

Amyopathic dermatomyositis is the cutaneous form of dermatomyositis that can occur without evidence muscle involvement from the autoimmune disease. It’s sometimes also called “dermatomyositis siné myositis”. To meet criteria for amyopathic dermatomyositis, skin findings should be present for at least 6 months. In this case, the patient had signs of dermatomyositis based on the presence of Gottron’s papules noted by the scaly erythematous eruptions and red patches overlying the knuckles only.

How common is amyopathic dermatomyositis?

Approximately 10-20% of cases of dermatomyositis present as this cutaneous-only variant in rheumatology clinics (3). This percentage may be higher in patients who are sent to their dermatologist first.

What other tests should you order?

Patients often have many lab abnormalities that are seen in classic dermatomyositis though creatine phosphokinase and myoglobin levels are more likely to be normal given the lack of muscle involvement.  While there is an increase risk of malignancy in middle-ages patients who present with classic dermatomyositis, it is unclear if this risk is present in patients with amyopathic dermatomyosits (7). Patients should continue to be monitored for progression from amyopathic dermatomyositis to the full disease.

What is the treatment and prognosis of amyopathic dermatomyositis?

If limited to small area of skin, highly potent topical steroids can used. If the patient has more systemic findings (e.g. fatigue) and extensive involvement immunosuppressive medications (e.g. prednisone, azathioprine and methotrexate) may be used.


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