Long-term renal function in adult patients with phenylketonuria

Introduction. In phenylketonuria (PKU) toxic phenylalanine (Phe) can harm other organs beyond the brain. Furthermore, the lifelong therapy of PKU consists of consumption of increased amounts of amino acid mixture that provoke hyperfiltration in glomeruli. Therefore, the adherence to therapy in PKU might influence the long-term kidney function in PKU patients.Methods. Data from 41 adult, early treated PKU patients were analyzed in this 10-year, retrospective, monocentric study. Two subgroups were created according to their therapy-adherence: one with long-term blood Phe levels in the therapeutic range (<600 mu mol/l), and one with suboptimal blood Phe levels. Renal function and metabolic parameters were collected over 10 years. Kidney function parameters were compared between the two groups and associations between blood Phe levels and kidney function were tested.Results. After 10 years, serum creatinine levels (p=0,369) and estimated glomerular filtration rate (eGFR) (p=0,723) did not change significantly from baseline in the good therapeutic group. The suboptimal therapeutic group's eGFR decreased in the same period (from 110.4 +/- 14 ml/min/1,73 m(2) to 94.2 +/- 16 ml/min/1.73 m(2), p = 0.017). At 10 years the suboptimal therapeutic group had an increased serum creatinine level (81 +/- 14.4 mu mol/L vs. 71.5 +/- 13 mu mol/L vs., p=0.038), and a decreased eGFR (94.2 +/- 16 ml/min/1.73 m2 vs. 103.3 +/- 13 ml/min/1.73 m(2) p=0.031) compared to the good adhering group. Significant negative correlation between Phe levels and eGFR (r=-0.41, p=0.008) was observed.Conclusion. Long-term suboptimal therapy adherence in PKU patients with high blood Phe levels may lead to deteriorations in kidney function.