Leg ulcer from necrotising vasculitis on the ankle of a 89 year old male patient. Necrotising vasculitis, or systemic necrotizing vasculitis (SNV), causes inflammation of blood vessel walls, which can interrupt normal blood flow. This leads to skin and tissue damage (depending where the affected blood vessels are located), including necrosis (tissue death). It is a rare disease, thought to be caused by autoimmune reactions (own antibodies attack the body's tissues). It leads to skin discolouration, and painful lesions, often appearing on the legs. Corticosteroids (steroidal medication) may be prescribed to reduce inflammation.