Joseph Junewick, MD FACR
over 4 years ago
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Heather Borders, MD
|Diagnostic Category: Infectious-Inflammatory
|Created: over 4 years ago
|Updated: over 4 years ago
8 year old female with muscle pain and weakness
Symmetric T2 hyperintensity and enhancement involving all visualized musculature. There was relative sparing of hamstrings and gluteals. Mild reticular subcutaneous edema. No abscess or other finding to suggest infection.
Dermatomyositis is an idiopathic inflammatory myopathy of striated muscle and skin. There is a characteristic skin rash and characteristic changes on muscle biopsy. Peak pediatric age is 5-14 years.
Five diagnostic criteria: symmetric proximal muscle weakness, characteristic muscle biopsy changes, laboratory changes, skin rash, emg abnormality.
Imaging findings are not included in these five major diagnostic criteria but the distribution on imaging is suggestive and can help direct biopsy.
The differential includes: infectious myositis, post traumatic myositis, subacute denervation, radiation therapy.
Imaging demonstrates increased fluid signal within the pelvic and thigh (proximal>distal) musculature with relative sparing of the hamstrings and gluteals. There is commonly enhancement with contrast. Reticular signal abnormality may be demonstrated in the subcutaneous fat. Changes are typically bilateral and symmetric. Chronically, there may be soft tissue calcification, which may become sheet like. Also, chronic muscle atrophy/fatty replacement.
Patients may develop interstitial lung disease. There is an association with malignancy. Treatment is with corticosteroids and patients may develop AVN.
StatDx: Dermatomyositis. Christopher Anton.
MRI imaging in children with Dermatomyositis. Hernandez et al. 161 (2): 359. (1993)