Age / Sex : 57 / M

Polymyositis

Discussion

Answer:  inflammatory myopathy (polymyositis,
dermatomyositis).

Findings:

Diffuse bilateral
edema of muscles of thigh, pelvic girdle, back, proximal shoulder.

Differential Diagnosis:

inflammatory
myopathy (polymyositis, dermatomyositis), infectious myositis, diabetic
myonecrosis, rhabdomyolysis, contusion.

Diagnosis:
polymyositis (biopsy positive, elevated LDH, CPK, Myoglobin), early phase

Discussion:

1)    
Idiopathic
inflammation and damage to skeletal muscle, with elevated muscle-derived
proteins.

2)    
Bilateral
symmetric involvement of skeletal muscle

3)    
Proximal
muscles (thigh and pelvic girdles), progressing to upper limb muscles

4)    
Radiographs
may show soft tissue calcifications (20-50%), classically described as sheet-like.

5)    
MR imaging
modality of choice for early diagnosis and choice of biopsy site.

-Muscle inflammation shows high signal
on fluid-sensitive sequences. No mass or architectural distortion. T1WI may
show decreased muscle bulk or high SI due to atrophy or fatty infiltration as a
sequelae of myositis.   

-Subcutaneous edema can be seen prior
to clinical evidence of skin rash

References:

 근골격 영상의학 (범문 에듀케이션, 강흥식 외)

 Diagnostic Imaging, musculoskeletal,
nontraumatic disease (Amyrsis, Manaster et al)