Whole-body MRI for full assessment and characterization of diffuse inflammatory myopathy

BACKGROUND Conventional magnetic resonance imaging (MRI) is a highly valuable tool for full assessment of the extent of bilateral symmetrical diffuse inflammatory myopathy, owing to its high sensitivity in the detection of edema which correlates with, and sometimes precedes, clinical findings. PURPOSE To evaluate the use of whole-body (WB)-MRI in characterization and full assessment of the extent and distribution of diffuse inflammatory myopathy. MATERIAL AND METHODS A prospective study on 15 patients presenting with clinical evidence of inflammatory myopathy. It included 4 boys/men and 11 girls/women (age range, 6-44 years; mean age, 25.5 years). 1.5 T WB-MRI was performed and the distribution and extent of disease severity was assessed according to muscle edema on STIR images. RESULTS Four cases of dermatomyositis showed lower limb disease predilection with edema in gluteal, thigh, and calf muscles. The same finding was seen in one case with recurrent polymyositis and three cases with overlap myositis with systemic lupus erythematosus (SLE). Bilateral upper and lower limb myositis was demonstrated in three cases of polymyositis and one case of overlap myositis with scleroderma. Bilateral edema involving all scanned muscle groups was detected in three cases of polymyositis with paraneoplastic syndrome, SLE, and severe active dermatomyositis (including the neck muscles). CONCLUSION WB-MRI is the diagnostic modality of choice for cases of inflammatory myopathy. It accurately detects the most severely affected muscles candidate for biopsy and provides a reliable baseline study for follow-up of disease progression as well as response to treatment.