[Differential diagnosis of a vasculitic syndrome of the lower limb].
Vasculitides can present with various clinical signs and symptoms. Besides disease-specific organ manifestations, the skin, peripheral nerves and musculature are frequently involved. The combination of elevated serological inflammatory markers, vasculitic skin lesions, active polyneuropathy and immobilizing myalgia of the lower limb musculature is highly suspicious for muscular polyarteritis nodosa (mPAN). Based on the case of a 63-year-old female patient with a vasculitic syndrome confined to the lower limb due to mPAN, important differential diagnoses of the these disease manifestations are discussed. Magnetic resonance imaging of the affected muscles and subsequent muscle biopsy (including skin and fascia) provide the relevant diagnostic data.