A 42-year-old woman presents to the emergency department with a 10-day history of progressive dyspnea, hemoptysis, and productive cough. She reports no prior medical history and takes no medications. Vital signs: temperature 37.4°C, blood pressure 148/92 mmHg, heart rate 102/min, respiratory rate 24/min. Physical examination reveals bilateral diffuse rhonchi. Chest X-ray shows bilateral patchy alveolar infiltrates. Laboratory studies reveal: serum creatinine 2.5 mg/dL (baseline 0.8 mg/dL), urinalysis with 3+ proteinuria, 3+ hematuria, and numerous RBC casts. Serum anti-glomerular basement membrane (anti-GBM) antibody is positive. Kidney biopsy shows crescentic glomerulonephritis with linear IgG deposition along the glomerular basement membrane on immunofluorescence microscopy. Which of the following is the most appropriate initial treatment?

1. A)Plasmapheresis, cyclophosphamide, and high-dose corticosteroidsGABARITO
2. B)Corticosteroids and mycophenolate mofetil alone
3. C)Hemodialysis and observation for spontaneous remission
4. D)High-dose corticosteroids and azathioprine without plasmapheresis
5. E)Rituximab monotherapy targeting B-cell populations