A 17-year-old boy comes to the physician because of edema of both legs as well as pen- orbital edema There is no history of diarrhea and no urinary symptoms suggestive of infection. He had a throat infection 3 weeks ago. His blood pressure is 110/70 mmHg. He undergoes a kidney biopsy and light microscopy is normal. The patient is treated and makes a full recovery. Which of the following is the most likely diagnosis?