Different aspects of magnetic resonance imaging of muscles between dermatomyositis and polymyositis

Sofia Silveira de Castro Miranda Daniel Alvarenga João Carlos Rodrigues Samuel Katsuyuki Shinjo About the authors


Although dermatomyositis (DM) and polymyositis (PM) share many clinical features in common, they have distinct pathophysiological and histological features. It is possible that these distinctions reflect also macroscopically, for example, in muscle alterations seen in magnetic resonance images (MRI).


To compare simultaneously the MRI of various muscle compartments of the thighs of adult DM and PM.


The present study is a cross-sectional that included, between 2010 and 2013, 11 newly diagnosed DM and 11 PM patients (Bohan and Peter's criteria, 1975), with clinical and laboratory activity.They were valued at RM thighs,T1 and T2 with fat suppression, 1.5 T MRI scanner sequences.


The mean age at the time of MRI, the time between onset of symptoms and the realization of the MRI distribution of sex and drug therapy were comparable between the two groups (p>0.050). Concerning the MRI, muscle edema was significantly found in DM, and mainly in the proximal region of the muscles. The area of fat replacement was found predominantly in PM. The partial fat replacement area occurred mainly in the medial and distal region, whereas the total fat replacement area occurred mainly in the distal muscles. There was no area of muscle fibrosis.


DM and PM have different characteristics on MRI muscles, alike pathophysiological and histological distinctions.

Dermatomyositis; Muscle diseases; Polymyositis; Magnetic resonance

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