A mother brings her 18-year-old son into the physician for a routine physical examination before starting college. He has no past medical history, does not take any medications, and denies any current symptoms. His vitals and physical examination are completely normal; however, a urine dipstick is positive for 1+ protein. A urine protein to creatinine ratio estimates that he is excreting 220 mg of protein per day. The patient has another urine sample collected 1 week later that shows persistent proteinuria.
Which of the following is the most likely cause of proteinuria in this patient?
A. Orthostatic proteinuriaOrthostatic proteinuria. Orthostatic proteinuria is a very common condition in children and adolescents and has a benign course that usually resolves with time. It is the most common cause of isolated proteinuria in this age group and is diagnosed by comparing urine protein excretion while lying down (e.g., first morning void) and standing up. (B) Minimal change disease is the most common cause of nephrotic syndrome in children; however, glomerular disease is a less common cause of proteinuria in children and adolescents. There would be much higher levels of proteinuria in this condition and likely some physical manifestations (e.g., periorbital edema). (C) AIN would be suggested by intrinsic AKI, WBCs or WBC casts in the urine, and urine eosinophils. (D) Fever, exercise, and dehydration are some of the causes of transient proteinuria, which is also very common in this age group and resolves after the causative factor is removed. However, this patient has persistent proteinuria.