Chronic kidney disease in adolescent and adult patients with phenylketonuria

J Inherit Metab Dis. 2013 Sep;36(5):747-56. doi: 10.1007/s10545-012-9548-0. Epub 2012 Nov 9.


Objectives: A lifelong phenylalanine-restricted diet with supplementation of a phenylalanine-free amino acid formula is recommended in patients with phenylketonuria (PKU). The effect of a long-term PKU diet on renal function and blood pressure has not been investigated yet.

Design: We analyzed renal function in 67 patients with PKU, aged 15-43 years, by measuring glomerular filtration rate (GFR) and effective renal plasma flow by isotope clearance ((51)Cr-EDTA, (123)J-Hippuran), estimated GFR, blood retention parameters, urinary protein and electrolyte excretion. Renal ultrasound and 24 h ambulatory blood pressure monitoring were performed additionally. Patients were divided into three groups according to their: 1) current diet (CD), i.e., daily protein intake: ICD <0.8 g/kg, IICD 0.8-1.04 g/kg, IIICD >1.04 g/kg; 2) life-long diet time (LDT), i.e., cumulative years of life in which daily protein intake exceeded dietary recommendations: ILDT <15 years, IILDT 15-19 years, IIILDT >19 years.

Results: GFR was decreased in 19 % of the patients. With increasing protein intake, GFR decreased significantly (ICD 111 ml/min; IICD 105 ml/min; IIICD 99 ml/min. ILDT 112 ml/min; IILDT 103 ml/min; IIILDT 99 ml/min). Proteinuria was detected in 31 %, microalbuminuria in 7 %, and hypercalciuria in 23 % of the patients. 23 % of the patients had arterial hypertension, and 41 % revealed a nocturnal non-dipping status.

Conclusions: In patients with PKU on a lifelong diet we could detect impaired renal function in 19 %, proteinuria in 31 %, and arterial hypertension in 23 %. Thus, chronic kidney disease may develop in PKU patients, and routine renal function tests should be performed during long-term follow-up.

MeSH terms

  • Adolescent
  • Adult
  • Blood Pressure / physiology
  • Cross-Sectional Studies
  • Diet, Protein-Restricted / adverse effects
  • Female
  • Glomerular Filtration Rate / physiology
  • Humans
  • Hypertension / physiopathology
  • Male
  • Phenylketonurias / physiopathology*
  • Phenylketonurias / urine*
  • Proteinuria / physiopathology
  • Proteinuria / urine
  • Renal Circulation / physiology
  • Renal Insufficiency / physiopathology
  • Renal Insufficiency / urine
  • Renal Insufficiency, Chronic / urine*
  • Young Adult