Glomerular Diseases USMLE Step 1 Practice Question

A 24-year-old woman with no significant past medical history presents to clinic with 3 weeks of progressive lower extremity edema and foamy urine. She denies recent infections, weight loss, or joint pain. Vital signs are stable (BP 118/76 mmHg, HR 88). Laboratory studies show: 24-hour urine protein 5.8 g, serum albumin 2.1 g/dL, serum creatinine 0.9 mg/dL, BUN 16 mg/dL, lipid panel shows hyperlipidemia, and serum complement levels (C3, C4) are normal. Antinuclear antibody and ANCA serologies are negative. Kidney biopsy findings include: normal glomerular architecture on light microscopy, negative immunofluorescence microscopy, but electron microscopy demonstrates diffuse, complete effacement of podocyte foot processes. Which of the following is the most likely diagnosis?