Muscular polyarteritis nodosa.

We present an unusual case of a 26-year-old man with muscular polyarteritis nodosa (PAN) with severe calf pain and gait disturbance. Magnetic resonance imaging of the lower limbs demonstrated highly increased signal intensity in both soleus muscles and the lateral head of the left gastrocnemius muscle. Biopsies of the soleus muscle showed acute necrotizing arteritis. The calf pain and limited range of motion of ankle dorsiflexion subsided from day 1 on administration of oral corticosteroid at high dosage and were completely resolved by 4 months. After tapering corticosteroid to 10 mg, symptoms recurred. A combined regimen of immunosuppressants was found to maintain symptomatic relief.Muscular PAN should be included in the differential diagnosis of a patient presenting with symptoms of acute or subacute calf pain. Although this muscular PAN was so far been benign, complete remission of the underlying process may be difficult to achieve.