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

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

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 the likely diagnosis?

20160226_161330

 

Answer –> Amyopathic dermatomyositis

 

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.

 

What are other signs of amyopathic dermatomyositis?

Many patients have fatigue. There may be photosensitivity. All signs you might see in classic dermatomyositis  (than muscle weakness) can be present which include:

Heliotrope rash (

Heliotrope rash: periorbital erythema, usually bilateral. (4)

 

Shawl or V-sign

Shawl or V-sign: erythema in the distribution of where a shawl sits but often limited to one region such as in this image of the anterior chest. (6)

 

Gottron's papules

Another example of Gottron’s papules. As noted before, Gottron’s papules are characterized by scaly erythematous eruptions and red patches overlying the knuckles only, usually sparing the spaces in between (5).

 

What other differentials might you consider with you suspect Gottron’s papules?

Gottron’s papules are unique to dermatomyositis and its variants (such as amyopathic dermatomyositis). However, are a couple things to consider. Psoriasis can cause erythematous scaly lesions but often not limited to the back of the hands and to the knuckles like Grotton’s papules are. Psoriasis will often cause nail pitting as well. The most similar presentation to Gottron’s papules can be found in knuckle pads where a patient will bite or chew on their knuckles (image below). This is often associated with an anxiety disorder such as general anxiety disorder or panic disorder.

knukle pads Comb

Knuckling pads (2)

 

What happened to our patient?

He was started on a high-potency topical steroids with positive response (noted below). He will continue with the topical cream and follow with his doctor to observe for transformation to full disease.

20160406_221917

Post therapy with topical steroids after one month.

 

Learn more about the hand exam? Visit our Approach to the Hand Exam page here!

 

 

Source/References:

  1. This case was obtained from Stanford School of Medicine (Errol Ozdalga, MD)
  2. Knuckling pad case from Journal of Medical Cases
  3. Jorizzo JL. Dermatomyositis: practical aspects. Arch Dermatol 2002; 138:114.
  4. Heliotrope rash by Elizabeth M. Dugan, Adam M. Huber, Frederick W. Miller, Lisa G. Rider via Wikipedia
  5. Gottron’s papules by Elizabeth M. Dugan, Adam M. Huber, Frederick W. Miller, Lisa G. Rider via Wikipedia
  6. Shawl sign by Elizabeth M. Dugan, Adam M. Huber, Frederick W. Miller, Lisa G. Rider via Wikipedia
  7. Elizabeth Ghazi, MS, Richard D. Sontheimer, MD, and Victoria P. Werth, MD. The importance of including amyopathic dermatomyositis in the idiopathic inflammatory myositis spectrum. Clin Exp Rheumatol. 2013 Jan-Feb; 31(1): 128–134.