Volumetric brain reductions in adult patients with phenylketonuria and their relationship with blood phenylalanine levels.

BACKGROUND: Continued dietary treatment since early diagnosis through newborn screening programs usually prevents brain-related complications in phenylketonuria (PKU). However, subtle neurocognitive and brain alterations may be observed in some adult patients despite early treatment. Nevertheless, neuropsychological and neuroimaging studies in the field remain scarce. OBJECTIVES: This work aimed to determine possible neuropsychological and structural brain alterations in treated adult patients with PKU. METHODS: Thirty-five patients with PKU and 22 healthy controls (HC) underwent neuropsychological assessment and T1-weighted magnetic resonance imaging on a 3 T scanner. FreeSurfer (v.7.1) was used to obtain volumetric measures and SPSS (v27.0.1.0) was used to analyze sociodemographic, neuropsychological, volumetric, and clinical data (p < 0.05). RESULTS: Adult patients with PKU showed significantly lower performance than HC in Full Scale IQ (t = 2.67; p = .010) from the WAIS-IV. The PKU group also showed significantly lower volumes than HC in the pallidum (U = 224.000; p = .008), hippocampus (U = 243.000; p = .020), amygdala (U = 200.000; p = .002), and brainstem (t = 3.17; p = .006) as well as in total cerebral white matter volume (U = 175.000; p = .001). Blood phenylalanine (Phe) levels in PKU patients were negatively correlated with the pallidum (r = -0.417; p = .013) and brainstem (r = -0.455, p = .006) volumes. CONCLUSIONS: Adult patients with early-treated PKU showed significantly lower global intelligence than HC. Moreover, these patients showed reduced global white matter volume as well as reductions in the volume of several subcortical grey matter structures, which might be related to the existence of underlying neurodevelopmental alterations. Higher blood Phe levels were also negatively correlated with pallidum and brainstem, suggesting a higher vulnerability of these structures to Phe toxicity.

The role of phenylalanine levels in the neuropsychological and neuroanatomical status of adult patients with phenylketonuria: The impact of fluctuations.

We aimed to evaluate the role of plasma phenylalanine (Phe) levels and its fluctuations in some neurocognitive domains and brain magnetic resonance imaging (MRI) findings in adult patients with phenylketonuria (PKU). It was an observational study that included patients older than 18 years with early-treated classical PKU. Plasma Phe levels were measured every other month throughout 2 years and predictor variables were the mean, maximum (max), minimum (min), range (min-max), and plasma Phe levels at the time of cognitive testing. Patients were evaluated for executive function, processing speed, visual attention, and fluid cognitive abilities using the Trail Making Test (TMT) and for the presence of brain MRI abnormalities. In all, 22 patients with a mean age of 34 years were included, of which 18 (81%) were women. Patients with higher range and maximum Phe levels had a poorer time-based performance on TMT form A and form B. Patients with brain MRI abnormalities had higher range, maximum, and mean Phe levels. Range of Phe levels showed a good performance for MRI abnormalities (area under the curve (AUC): 0.881, standard error (SE): 0.095, 95% CI: 0.695-0.999, p = 0.044) and for the poorest time-based performances on TMT form A (AUC: 0.822, SE: 0.092, 95% CI: 0.641-0.999, p = 0.024) and B (AUC: 0.816, SE: 0.094, 95% CI: 0.632-0.999, p = 0.021). Greater Phe variability may have a negative impact on some neurocognitive domains and could be related to the severity of brain structural damage in adult patients with PKU.

The correlation of lipid profile and waist circumference with phenylalanine levels in adult patients with classical phenylketonuria.

INTRODUCTION AND OBJECTIVES: Some studies have pointed to a relationship between Phenyketonuria (PKU) and an increased cardiovascular risk (CVR). This study aimed to evaluate the influence of metabolic control on classical CVR factors in adult patients with PKU. MATERIAL AND METHODS: It was a cross-sectional study conducted in patients older than 18 years with a diagnosis of classical PKU and under strict dietary control. Demographic, epidemiological and laboratory variables related to CVR were collected. The variables of metabolic control were some parameters related to phenylalanine (Phe) plasma levels. RESULTS: A total of 47 patients were included with a mean age of 36±10 years of which 30 (64%) were women. Multivariate analysis revealed that range Phe (B=-2.211, P=0.044, 95%CI: -4.354-(-0.068)) levels were within the model for triglyceride concentrations, while minimum (B=-2.803, P=0.051, 95%CI: -5.612-0.007) and range (B=-1.515, P=0.039, 95%CI: -2.945-(-0.084)) Phe levels were within the model for high-density lipoprotein cholesterol concentrations. Median Phe levels showed a stronger correlation with waist circumference (WC) (B=1.216, P=0.002, 95%CI: 0.462-1.969) than with body mass index (B=0.355, P=0.052, 95%CI: -0.004-0.714). CONCLUSIONS: High Phe levels and wide Phe fluctuations were related to weight gain, increased WC and lipid profile abnormalities. Systematic CVR assessments and comprehensive monitoring of Phe levels may be desirable to prevent or delay cardiovascular disease in PKU patients.