Differential diagnosis included traumatic muscle injury with hematoma, infectious myositis
, myositis ossificans, and soft tissue neoplasm.
As the inflammatory markers doubled in a short interval, repeat lower extremity MRI was obtained to rule out abscess or infectious myositis
. T1-weighted imaging on MRI noted diffuse swelling and edema-like signal involving the right thigh musculature with fluid-like signal at the fascial planes without any focal fluid collection (Figure 2).
 In the differential diagnosis, rather than infectious myositis
being first considered, patients are tested for diabetes or immune system problems.
The patient presented with dark discoloration of the urine, and was admitted to a regional hospital in the second week of February with the diagnosis of suspected infectious myositis
Although small, the presence of soft tissue masses was a clue pointing toward a neoplastic process and would be atypical for inflammatory or infectious myositis
. These nodules were located over the buttocks, an unusual site for lymph nodes.
CT imaging is a helpful tool in distinguishing NIF from the most common infections of the soft tissues such as cellulitis, nonnecrotizing fasciitis, soft tissues abscess, infectious myositis, and osteomyelitis where there is an involvement of the bone adjacent to the infection .
When there is an infectious myositis, on CT, there are enlargement and decreased attenuation of the affected muscle with effacement of surrounding planes.