Double-Positive Anti-GBM and ANCA-MPO Vasculitis Presenting With Crescentic Glomerulonephritis

We report the case of a 61-year-old man with rapidly progressing glomerulonephritis (RPGN) due to double-positive anti-neutrophil cytoplasmic antibodies (ANCA) and anti-glomerular basement membrane antibodies (GBM) vasculitis. The past medical history included stable untreated psoriatic arthritis and arterial hypertension. He presented with asthenia, anorexia, and rapidly deteriorating renal function with metabolic acidosis and hyperkalemia evolving with the need for hemodialysis. No nephrotoxic drugs were identified. Urinalysis showed proteinuria, erythrocyturia, and mild leukocyturia with no pathological casts and renal ultrasound excluded obstruction as the cause of the acute kidney injury. The subsequent study established the diagnosis of double-positive ANCA and anti-GBM vasculitis with renal biopsy confirming the presence of crescentic glomerulonephritis. The patient was started on corticosteroids, cyclophosphamide, and plasmapheresis with the improvement of symptoms and decrease of antibody titers. The renal function recovery was not obtained and referral for transplantation is ongoing.