Dermatomyositis is an auto immune inflammatory myositis.
There is a recognised female predilection.
It has a bimodal age of presentation depending on the variant:
- juvenile dermatomyositis (JDM) : affects children and tends to be more severe;
- adult dermatomyositis (ADM) : typically affects adults around the age of 50.
There is cell mediated injury targeted at striated muscle with resultant atrophy, oedema, coagulation necrosis, fibrosis and calcification.
- elevlated muscle enzymes (CK)
- elevated muscle specific antibodies
- anti RNA
- anti Mi2
- interstitial lung disease 2 : typically gives a patchy and subpleural consolidation with parenchymal bands.
- internal malignancy 1 : can occur as part of a paraneoplastic syndrome (e.g lung cancer)
- typically shows dystrophic calcification in muscles and soft tissues (calcinosis universalis)
- sheet like although at least four patterns have described with childhood dermatomyositis 4.
- classically seen affecting the thigh regions
- chest radiograph may show diaphragmatic elevation
- may show disordered peristalsis involving the upper oesophagus : portion supplied by skeletal muscle
T2 : generally hyper intense signal throughout the affected muscles ; calcific areas may be low signal ; perimuscular oedema may additionally appear as high signal ; signal intensity may return to normal after treatment 4.
General imaging differential considerations include
- polymyositis : doesn't affect skin
- 1. Kubo M, Ihn H, Yamane K et-al. Serum KL-6 in adult patients with polymyositis and dermatomyositis. Rheumatology (Oxford). 2000;39 (6): 632-6. doi:10.1093/rheumatology/39.6.632 - Pubmed citation
- 2. Mino M, Noma S, Taguchi Y et-al. Pulmonary involvement in polymyositis and dermatomyositis: sequential evaluation with CT. AJR Am J Roentgenol. 1997;169 (1): 83-7. AJR Am J Roentgenol (abstract) - Pubmed citation
- 3. Akira M, Hara H, Sakatani M. Interstitial lung disease in association with polymyositis-dermatomyositis: long-term follow-up CT evaluation in seven patients. Radiology. 1999;210 (2): 333-8. Radiology (full text) - Pubmed citation
- 4. Blane CE, White SJ, Braunstein EM et-al. Patterns of calcification in childhood dermatomyositis. AJR Am J Roentgenol. 1984;142 (2): 397-400. AJR Am J Roentgenol (abstract) - Pubmed citation
- 5. Hernandez RJ, Sullivan DB, Chenevert TL et-al. MR imaging in children with dermatomyositis: musculoskeletal findings and correlation with clinical and laboratory findings. AJR Am J Roentgenol. 1993;161 (2): 359-66. AJR Am J Roentgenol (abstract) - Pubmed citation
- 6. Tomasová studynková J, Charvát F, Jarosová K et-al. The role of MRI in the assessment of polymyositis and dermatomyositis. Rheumatology (Oxford). 2007;46 (7): 1174-9. doi:10.1093/rheumatology/kem088 - Pubmed citation
Synonyms & Alternative Spellings
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