Minimal Change Disease and Phenylketonuria in an Adult Patient: The Two Sides of Protein Homeostasis.

Phenylketonuria (PKU), the most common inborn error of amino acid metabolism, has been associated with an increased risk of renal impairment, the reason for which is not fully understood. We report the case of a 33-year-old female patient diagnosed with PKU in adulthood after suspicion of the disease in her daughter. The diagnostic approach revealed proteinuria, and minimal change disease (MCD) was identified. Therapeutic measures and follow-up are discussed. The possible link between these two disorders is interesting. Attenuated developmental delay of untreated PKU could be explained by the decreased accumulation of phenylalanine secondary to proteinuria. On the other hand, MCD may be a possible, although as yet unreported, pathophysiological mechanism explaining the renal repercussions that have been found in adult PKU patients, who should be screened for proteinuria. LEARNING POINTS: Phenylketonuria (PKU) is associated with renal impairment so patients with PKU should be periodically screened for proteinuria because podocytopathies, such as minimal change disease (MCD), may be an underlying misdiagnosed condition.MCD in adults demands tight surveillance in case of severe complications including nephrotic syndrome, haematuria and acute kidney injury, and although remission with glucocorticoid therapy is typical, 50-75% of patients will relapse.MCD may be a previously unreported cause of proteinuria and renal involvement in adult patients with PKU, where control of hypertension and moderation of protein overload are essential.