A 14-year-old boy presents to the hospital with severe leg swelling that started 2 weeks ago. He also notes feeling tired and having little energy to play sports with his friends. His past medical history is negative and he is not taking any medications.On examination, his blood pressure is 163/96 mm Hg, and there is pedal edema up to his knees, as well as periorbital edema. His remaining clinical exam is normal. A urinalysis is positive for 3+ proteinuria and on 24-hour urine collection the total protein excretion is 5.4 grams/day. He undergoes a renal biopsy and there are no changes seen on light microscopy, but electron microscopy shows foot process fusion and no deposits on the membranes. Which of the following is the most likely diagnosis?