Positron Emission Tomography (PET) in Phenylketonuria: A Systematic Review of Brain Metabolism Beyond Phenylalanine.
Yutaka Furuta, Shoji Yano, John A Phillips et al.
✦ AI-curated · Sources linked
In 30 seconds
This systematic review assessed PET studies of brain metabolism and neurotransmitter-related processes in people with phenylketonuria or hyperphenylalaninemia. Following a PRISMA-guided search, 13 studies were included; their mean sample size was 8.8 (median 6). Findings varied by tracer: FDG studies showed regionally heterogeneous glucose-metabolism abnormalities independent of plasma phenylalanine (Phe), amino acid studies indicated reduced cerebral protein synthesis, and fluorodopa-related studies suggested reduced dopaminergic activity without significant correlation between plasma Phe and striatal fluorodopa utilization. The review identifies PET as a potential CNS biomarker, while emphasizing that further research is needed.
Key findings
- The review included 13 studies, with a mean sample size of 8.8 (median 6).
- FDG PET studies found regionally heterogeneous brain glucose-metabolism abnormalities independent of plasma Phe levels.
- Amino acid PET studies indicated reduced cerebral protein synthesis associated with impaired large neutral amino acid transport and increased brain Phe.
- Fluorodopa-related PET studies suggested reduced dopaminergic activity, with no significant correlation between plasma Phe and striatal fluorodopa utilization.
Why it matters
Blood Phe levels do not directly establish CNS neurotransmitter concentrations, and reliable CNS biomarkers are lacking. PET findings suggest that brain metabolic and neurotransmitter-related changes may not be captured by peripheral Phe measurements alone. This could help frame future investigations of the relationship between biochemical control and neurological function, although the current evidence does not establish clinical utility.
What to keep in mind
The evidence base was small, with heterogeneous metabolic control, restricted tracer availability, predominantly cross-sectional designs, and limited correlation with clinical signs and symptoms.