Soru

A 45-year-old man presents to the clinic for the evaluation of progressive lower extremity swelling over the past three weeks. He has no significant past medical history and takes no medications. Vital signs are within normal limits. Physical examination demonstrates marked bilateral pitting edema extending to the knees. Laboratory evaluation reveals a serum albumin level of 2.2 g/dL and a serum creatinine of 0.8 mg/dL. Urinalysis demonstrates 4+ proteinuria with no hematuria or cellular casts. A 24-hour urine collection confirms 6.8 g of protein. A percutaneous renal biopsy is performed to establish the diagnosis. Light microscopy shows uniform, diffuse thickening of the glomerular capillary walls without an increase in cellularity. Jones methenamine silver staining highlights projections of basement membrane material, creating a "spike and dome" appearance. Immunofluorescence demonstrates a diffuse granular pattern of IgG and C3 deposition along the capillary loops. Which of the following is the most likely diagnosis?