An 11-year-old girl is brought to the doctor's office by her mother, who states that her daughter felt weak and had swollen face for 3 days. According to the mother, her daughter had always been healthy and tive until the onset of the symptoms. Physical examination reveals generalized swelling of the face and birtarg edema of the lower limbs. Upon inquiry, the girl describes a foamy appearance of her urine, but denies blood in urine, nycturia, or pain during urination. Laboratory studies show proteinuria and mica copic hematuria. Which of the following is the most likely cause of the findings in the laboratory analysis of urine?