Crescentic Glomerulonephritis with Dual Autoantibody Positivity in the Setting of Polycystic Kidney Disease

Introduction: This is the sole documented case of a patient with PCKD diagnosed with dual seropositive glomerulonephritis for anti-GBM and ANCA. Case Description: 71 yo M with PMH of PCKD, CKD3A, BPH, DM2, HTN, HLD, and PAD presented to the ED with bilateral leg edema, SOB, lightheadedness, fatigue, decreased urine production, flank pain and cough with hemoptysis. UA revealed elevated urine protein and a large amount of urine blood. Renal US showed multiple bilateral renal cysts. Chest CT showed bilateral infiltrates and pleural effusions. Pt developed anuria and metabolic acidosis and was started on HD. Pt was also dyspneic and hypoxic necessitating Bipap. Immunology was positivite for p-ANCA. Pt was started on IV methylprednisone 1g/day x 3 days then prednisone 40mg PO/day, rituximab 1g/day with plasmapheresis and MWF HD. Additional serology results were also positive for anti-GBM ab. Following a confirmatory renal biopsy, the patient was switched to cyclophosphamide 100mg/day. Anti-GBM ab levels began to downtrend from 8.0 to 5.1 with Rituximab treatment. Anti-GBM levels further decreased to 2.7 on Cyclophosphamide. During admission, he developed hemoptysis and hypoxia 2/2 to alveolar hemorrhage which required intubation. Pt suffered from multiple episodes of pulmonary effusions and hemothorax secondary to recurrent alveolar hemorrhage. Finally, he contracted COVID pneumonia during his admission. Ultimately, his POA decided to withdraw care due to poor prognosis, and unfortunately, pt expired shortly after extubation. Discussion: This case presents a unique diagnositic challenge as pt's baseline CKD3A 2/2 PCKD along with his initial clinical presentation was consistent with AKI leading to volume overload and pulmonary edema. Furthermore, GN rarely presents with PCKD with only 3 cases seen based on a literature review which may lead to cases such as this being easily overlooked.