Ultrasound for the rheumatologist - focal myositis.

A 70-year-old woman presented to our hospital with a 2 week history of progressive pain, swelling and re d ness of the left lower calf. The onset of pain was preceded by significant itching in that region. She denied trauma or prolonged immobilization. Her medical history was significant for sporadic episodes of recurrent focal myositis involving the left calf/soleus muscle, right triceps and the right rectus abdominis muscle over the preceding years with the last episode three years before the current clinical presentation. A rectus abdominis biopsy at that time showed scattered necrotic and rege nerating muscle fibers, few muscle fibers invaded by macrophages, few vessel walls invaded by mononuclear cells, and absence of fibrinoid necrosis suggestive of myopathy with necrosis and inflammation without vasculitis. Before our evaluation, ultrasound (US) evaluation elsewhere excluded deep venous thrombosis and a T1 and STIR magnetic resonance imaging (MRI) without contrast demonstrated left soleus ‘edema’ as well as subcutaneous edema. She was treated as a case of cellulitis with several courses of different antibiotics without any improvement. Erythema, warmth, swelling and extreme tenderness of her left calf were present on physical exam. Muscle strength was normal. Laboratory studies showed an ele vated erythrocyte sedimentation rate of 57 (normal <20 mm/hour), elevated C-reactive-protein of 154 (normal < 8 mg/L) and leukocytosis with a white count of 16.7 (normal <10.5x10/L) but normal muscle enzy mes. An MRI (Siemens Skyra, 3 Tesla) at our hospital suggested myositis involving only the left soleus with sparing of the surrounding musculature (Figure 1 and 2). The right lower extremity was normal. She declined Aslam F1, Fox M2, Chang-Miller A1