A tale of two vasculitides: biopsy-proven giant cell arteritis followed by the independent development of renal-limited microscopic polyangiitis.

We describe an 80-year-old woman who presented with headaches, bilateral jaw claudication and visual symptoms. She was diagnosed with giant cell arteritis, which was confirmed by temporal artery biopsy. She was treated with high-dose prednisone followed by a slow taper, with complete resolution of symptoms. Approximately 4 years later, she developed progressively worsening renal function associated with haematuria. Serological workup revealed a high-titre perinuclear antinuclear cytoplasmic antibody and antibodies to myeloperoxidase. Renal biopsy demonstrated a pauci-immune focal crescentic glomerulonephritis. Extensive review of systems, physical exam and diagnostic studies demonstrated no evidence of extra-renal disease, and she was diagnosed with renal-limited microscopic polyangiitis. High-dose prednisone was resumed, but she refused treatment with either cyclophosphamide or rituximab due to concern for toxicity. Her prednisone dose was tapered and renal function stabilised. Our case highlights the need to recognise the successive occurrence of two distinct vasculitides in a single patient and monitor accordingly.