A Case of Concurrent Membranous Nephropathy and Anti-GBM Disease

Introduction: Presentation of concurrent anti–glomerular basement membrane (anti-GBM) disease and membranous nephropathy (MN) is rare and has been described only in case reports. If not treated promptly, it can lead to end-stage kidney disease and can be life-threatening. Unfortunately, the optimal management strategy remains unclear. Herein, we report a patient in whom rituximab-based immunosuppressive regimen was used as first line treatment. Case Description: A 25-year-old man with a past medical history of vaping, marijuana use, anxiety and asthma presented with dark-colored urine for 3-4 weeks, cough for 1 week, and 5-days of hemoptysis. On initial evaluation, he was afebrile with HR 80 bpm, BP 147/91 mm Hg, RR 16/min, and O2 sat 99% on room air. Laboratory testing revealed white cell count 8500 cells/µL, hemoglobin (Hb) 9.6 g/dL, platelet count 268,000 per µL, and serum creatinine 2.47 mg/dL. Serology was elevated for anti-GBM antibody at 3.3 U/ml. Urinalysis showed Hb 3+ and protein 3+ with >50 red blood cells per high power field on microscopy. Urine protein to creatinine ratio was 4.47mg/mg. CT chest, abdomen and pelvis revealed bilateral infiltrates along with multiple nodular densities in the lungs. Due to worsening respiratory status with concern for diffuse alveolar hemorrhage, he was subsequently intubated. Kidney biopsy specimen showed focal necrotizing and crescentic glomerulonephritis, compatible with anti-GBM disease, and PLA2R-negative MN. He was treated with PLEX for 14 sessions, rituximab weekly for 4 doses, and pulse IV methyl prednisone 1 gm daily for 5 days followed by 6-month steroid taper with oral prednisone. Post-PLEX, respiratory status improved, anti-GBM antibody declined to 0.3 (normal <1), and serum creatinine stabilized at ~4.3 by discharge. By 8-months, he has developed progressive CKD to stage 5; however, he has remained off dialysis. Discussion: Patients with concurrent anti-GBM disease and MN can present with life-threatening pulmonary-renal syndrome. In our patient, although treatment with rituximab-based regimen improved respiratory status and resulted in serological improvement, his course was complicated by progressive kidney failure. This underscores the need for consideration of cyclophosphamide or other aggressive therapies to preserve kidney function in such patients.