A case of phenotypic and serological transformation in Wegener's granulomatosis.

Wegener's granulomatosis (WG) is a systemic vasculitis of small- to medium-sized arteries, associated with necrotizing granulomata classically involving the upper and lower respiratory tracts and kidneys. It is usually associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCA). ANCA-negative WG is usually a limited form of the disease that tends to affect organs other than the kidneys, often the central nervous system. We describe an unusual case presenting with ANCA-positive WG affecting the kidneys and upper airway that, despite standard treatment, demonstrated a phenotypic and serological transformation into an aggressive ANCA-negative WG affecting the central nervous system.