Seronegative anti-GBM Disease with Coexistent ANCA Positivity

Anti-glomerular basement membrane disease has been reported to coexist with anti-neutrophil cytoplasmic antibody (ANCA) positive vasculitis. Seronegative anti-GBM disease has been previously described and mostly blamed for the relative insensitivity of earlier serologic assays. A 58-year-old male was transferred to our facility for acute kidney injury. Prior to his hospital admission, the patient had a 2 week history of progressive fatigue, fevers, anorexia, vomiting, decreased urine output, sinus congestion, and non-productive cough. His creatinine reached 13 mg/dL. P-ANCA was positive, anti GBM antibody was negative twice, and urinalysis showed hematuria. Chest x-ray demonstrated diffuse opacities, concerning for pulmonary hemorrhage. Renal biopsy showed a severe necrotizing and crescentic glomerulonephritis with circumferential crescents. There was bright linear glomerular basement membrane staining with IgG consistent with anti-GBM disease. Given these findings, the patient was started on oral cyclophosphamide (160 mg daily), in addition to pulse dose methylprednisolone. He was also initiated on therapeutic plasma exchange. Due to worsening renal function, hemodialysis was started. The patient was discharged from the hospital and completed a course of treatment with cyclophosphamide and prednisone but remains oligo-anuric and hemodialysis dependent at 150 days since presentation. This case highlights the importance of tissue diagnosis in situations similar to this.