A Retrospective Case Series Analysis of the Relationship Between Phenylalanine: Tyrosine Ratio and Cerebral Glucose Metabolism in Classical Phenylketonuria and Hyperphenylalaninemia

We retrospectively examined the relationship between blood biomarkers, in particular historical mean phenylalanine to tyrosine (Phe:Tyr) ratio, and cerebral glucose metabolism. hypothesized that Phe:Tyr ratio would be more predictive of metabolism than (Phe) level alone. performed a retrospective case series analysis involving 11 adult classical phenylketonuria/hyperphenylalaninemia patients under care an Inherited Metabolic & Neuropsychiatry Clinic who had complained memory problems, collating casenote data from biochemistry, clinical [ 18 F]fluorodeoxyglucose positron emission tomography ([ F]FDG PET). The was calculated for individual samples summarized as standard deviation (SD-Phe:Tyr), each patient. Visual analyses PET revealed heterogeneous patterns hypometabolism eight patients. standardized uptake negatively correlated with Phe large cluster peak localized right superior parietal gyrus. Even larger clusters negative correlation encompassed most brain, frontal peaks, were observed Phe:Tyr, SD-Phe:Tyr. Our provides further evidence association hypometabolism. Mean its over time, appear indicative global problems Phe.