A 57-year-old woman, with a known history of dermatomyositis, was referred for MR imaging in the preoperative evaluation of large and bilateral painful gluteal soft tissue masses.
Diffuse, coarse calcifications were identified over the soft tissue mass on radiograph.
On MR, diffuse, mass–like calcified lesions were recognized in bilateral gluteal areas extending up to the anterior iliac crests, corresponding to the coarse calcifications revealed by the radiograph (Figure 1). The calcified lesions were hypointense on T2WI fat–saturated (Figure 2a) sequence with prominent signal voids on SWI sequence (Figure 2b). On DWI (800 b values) part of the lesions showed restricted diffusion (Figure 2c). After intravenous contrast administration mild enhancement was identified within the lesions as well as in the adjacent fascia, subcutaneous fat and cutis indicating active myositis, fasciitis and panniculitis (Figure 2d). There were no associated abscess collections.
Dermatomyositis is the commonest idiopathic inflammatory myopathy with a bimodal age distribution (<15 years and 45–54 years) and a female predominance. Diagnosis is based on classical cutaneous manifestations combined with autoantibodies that are myositis-specific, while some patients have anti-synthetase antibodies. The diagnosis is confirmed with skin or muscle biopsy. Muscle involvement in dermatomyositis is predominantly bilateral and symmetric and the most commonly affected muscles are those of the thigh and pelvic girdle [1]. MR findings of muscular involvement in the acute phase consists of intramuscular high signal intensity areas on fat-saturated T2 and STIR images that enhance after contrast administration on T1WI, with a diffuse, patchy, peripheral or honeycomb pattern, corresponding to oedema related to active inflammatory processes. On DWI the lesions show restricted diffusion due to active myositis, fasciitis and panniculitis. The same pattern of involvement may extend to adjacent fascia, subcutaneous and cutaneous tissues. In the chronic phase, myositis ossificans (MO), panniculitis ossificans (PO) and atrophy of the affected muscles may occur. Fatty atrophy of the muscles on T1WI and T2WI is identified as high signal intensity, suppressed in fat-saturated images [1,3,4]. MO is defined as abnormal development of subcutaneous and interfascial calcification that subsequently ossifies in a centrifugal pattern (5). The hypothesis that correlates to the pathophysiological substrate of heterotopic calcification may involve local muscular damage by trauma and inflammation and local vascular ischemia (6). Histology reveals the benign nature of the lesion, yet in a minority of cases the heterotopic ossification may give rise to the malignant counterpart, osteosarcoma (5). The ossifications in MO, seen as signal voids on SWI sequences, are peripherally located, in contrast to osteosarcoma in which they are located centrally[1,2]. PO lesions are located in the subcutis. Calcifications in the subcutaneous tissues can be subtle or overt and appear hypointense on all MR sequences with a surrounding rim of enhancement. On radiographs coarse, rim-like calcifications in soft tissues are seen within fatty metaplastic areas. The ossifications are distinct and distant from adjacent bony structures. Surgical intervention is indicated when there is functional limitation, persistent pain, neurovascular compromise or severe disfigurement. However, there is a risk of recurrence following resection.
Myositis ossificans and panniculitis ossificans developing in the substrate of dermatomyositis
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Extensive patchy and reticular calcifications are observed in the bilateral gluteal soft tissues. On X-ray, dense cloud-like calcifications can be seen in the soft tissues above both femoral greater trochanters, showing clear demarcation from the bony structures and remaining independent of them. MRI plain scan and contrast-enhanced sequences demonstrate multiple soft tissue masses in the bilateral gluteal muscle regions. In T2/STIR sequences, localized areas exhibit increased signal, with prominent enhancement at the margins and septa. DWI sequences reveal relatively restricted areas, suggesting active inflammatory changes. Overall, the imaging features are consistent with chronic inflammation and ectopic ossification (in the context of myositis/fasciitis).
Based on the patient’s past diagnosis (history of dermatomyositis), clinical symptoms (bilateral gluteal pain and soft tissue masses), and imaging findings (extensive cloud-like and patchy ectopic ossification in the bilateral gluteal soft tissues; MRI showing soft tissue edema and inflammatory response), the most likely diagnosis is: myositis ossificans and panniculitis ossificans related to dermatomyositis, accompanied by chronic inflammatory changes.
Rehabilitation training should emphasize a gradual and individualized approach. Main objectives include alleviating pain and inflammation, restoring muscle strength and bodily function, and preventing further soft tissue damage and ectopic ossification. An exercise plan according to the “FITT-VP” principle may be considered as follows:
During this process, closely monitor the patient’s cardiopulmonary function and musculoskeletal health. Owing to bone fragility and muscle inflammation, avoid excessive loads or intense impact activities to minimize the risk of further injury or recurrence of inflammation.
This report is a reference analysis based on currently available information and does not replace an in-person consultation or professional medical advice. Specific treatment decisions must be made by specialists, taking into account the patient’s actual condition.
Myositis ossificans and panniculitis ossificans developing in the substrate of dermatomyositis
