[Cutaneous vasculitis and vasculopathy : Differential diagnosis in biopsies of the lower extremities]

[Cocaine-induced vasculitis and mimics of vasculitis]

Cocaine is a psychotropic tropane alkaloid and stimulant drug. Nasal insufflation of cocaine powder is a common route of administration. In Germany, cocaine is frequently adulterated with levamisole, an anthelminthic drug with immunomodulatory effects. Both substances are linked to various autoimmune conditions. Cocaine-induced midline destructive lesions cause a progressive destruction of osteocartilaginous structures within the upper respiratory tract and can mimic localized granulomatosis with polyangiitis. In addition, systemic vasculitis due to cocaine and levamisole has been reported. Differentiation of these conditions from primary vasculitis can be challenging because antineutrophil cytoplasmic antibodies (ANCA) are commonly detected. Early diagnosis of these conditions is crucial as clinical improvement is closely related to drug cessation.

[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.