Diagnosing alkaptonuria-related nephropathy with urine albumin analysis

Homogentisic acid (HGA) accumulation in alkaptonuria (AKU) causes injuries in various organs including the kidney. We present a case of a 9-year-old girl initially diagnosed with AKU-related nephropathy due to proteinuria found in her urine analyses. Despite 1 month of ramipril treatment, the patient's proteinuria progressed, and as a result, kidney biopsy and nitisinone treatment were planned. In addition, we controlled her proteinuria with urine albumin measurement. After finding a normal urine albumin level in the 24-h urine sample, we realized that the patient was misdiagnosed with proteinuria because of HGA interference with urine protein level measurement using benzethonium. The patient's treatment for kidney injury was canceled. Urine albumin level was measured as normal 2 months later, confirming proteinuria was a false-positive test result. AKU-related nephropathy should be evaluated with urine albumin measurement instead of protein. In this way, the complication risk of unnecessary interventions and pharmacotherapies can be avoided.