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dermatomyositis (DM) in an adult

Posted by iskanbasal on June 26, 2007

Now I know better this condition, DERMATOMYOSITIS (DM) . It was the subject of the clinical conundrum: Are we there yet?”. An article by Lisa H. Williams, MD et al. from the journal of hospital medicine.
A 62-year-old man with psoriasis for more than 30 years presented to the emergency department with a scaly, pruritic rash involving his face, trunk, and extremities that he had had for the past 10 days. The rash was spreading and not responding to application of clobetasol ointment, which had helped his psoriasis in the past. He also reported mild pharyngitis, headache, and myalgias.

What made the case puzzling is the appearance of a new rash in a patient with a long standing psoriasis, more than 3 decades in this case. The lateness to consider it a new disease was the central point. I learned much about the rash of dermatomyositis from this article, sometimes it is different than its classical aspect as it was in this case which made it confusing. I can not upload the patient image because it is under copyright but it is striking either in the rash’s violaceous color or in its entity. However there are free images in Google images for the rash in dermatomyositis, this is one.And there are other images of the gottron’s papule . : (Violet-colored inflammation over the knuckles is an important diagnostic finding in dermatomyositis, since other skin conditions produce more redness). This is another dermatomyositis rash. The patient’s rash is however completely different: too much violaceous and scaly, and too much spread over the upper extremities, chest, neck and the whole face. The physicians team continued to treat the patient as for an exacerbation of his long standing psoriasis, and this was because many reasons: 1. his rash was atypical. 2. the onset of the rash was not accompanied with symptoms of myositis. Actually when myositis lastly appeared it directed the diagnostic process to suspect dermatomyositis.

What I also learned from this case presentation is the characteristic skin biopy findings in dermatomyositis: there is the interface dermatitis , i.e. an inflammatory infiltrate in the dermo-epidermal junction, it is considered pathognomic; it is only shared with lupus. The pathologists in this case failed to recognize it early. An important aspect in this diagnosis is that in adults 25% may develop malignancies, generally solid tumors at some point in the course of their disease. This patient had a gastric-type adenocarcinoma at the gastroesophageal junction and died few weeks after the onset of the rash. It was discovered after an upper endoscopy done to detect the reason of the patient’s persistent odynophagia. I don’t think an earlier diagnosis would have changed the prognosis of his principal illness. The other DM-associated malignancies are : 10-fold higher risk of ovarian cancer, and lung, gastric, colorectal, pancreatic carcinomas and non-Hodgkins lymphoma.

What the authors in this case did not mention are some concepts I have already studied on the ADAMS principles of neurology 8th ed during my course in clinica neurologica, i. e. the pathogenesis of dermatomyositis that makes it a different disease than polymyositis; both are the main inflammatory myopathies.

In dermatomyositis, the autoimmune reaction is predominantly humoral; there is the formation of antibodies and immune complexes and the attack is directed against targets situated on the endothelial cells of the small vessels and arterioles in the perifascicular area in the perimysium.

While in polymiositis the autoimmune reaction is mainly cellular; the attack is directed against targets situated on the muscle fiber membranes. we find the cellular infiltrate in the endomysium and there is necrosis of muscle fibers, myophagia and attempts of regeneration with the presence of aggregates of small and altered muscle fibers.

This what make the two conditions different, they have two different pathogenesis and the immune attack have different targets in each of the conditions.

So the diagnosis of DM is based on the presence of both the rash and symptoms of myositis, i.e. proximal muscle weakness, myalgias, fatigue. There is also dysphagia and odynophagia.

I also learned about the serologic testing in this disease,e.g. the antibody anti Jo-1, an antisynthetase antibody that predicts incomplete response to treatment and lung involvement. The pulmonary involvement from interstitial lung disease; the cardiac from conduction abnormalities.

DM when present in children has a different prognosis, not associated with malignancies, and it is characterized by sheet-like calcifications (calcinosis universalis) in the cutaneous, subcutaneous, and sometimes in the muscle itself.

Now as i finished my interest in DM , and the reading of this case study i think to publish these simple notes here in my blog. May I refer to it as a reference point.

(again , escuse me for English errors)


3 Responses to “dermatomyositis (DM) in an adult”

  1. filippo said

    thank you

  2. […] I posted below on dermatomyositis (DM) and this post reached the 2nd position in google search using the terms dermatomyositis and […]

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