Early exposure and early treatment support phenylalanine-related developmental injury in PKU. Adult challenge experiments, brain transport and discordant untreated outcomes refine vulnerability and reversibility; biochemical lowering and neurocognitive recovery remain separate endpoints.
This dated addendum adds selected evidence and tests that could resolve the remaining questions. It does not regrade the archived review.
Each question identifies a limit in the checked evidence. A missing search result alone does not establish a gap in the entire field.
Competing explanation: Blood phenylalanine may imperfectly reflect transport, protective modifiers or prior developmental exposure.
Discriminating test: Longitudinal brain spectroscopy, genotype and exposure histories in prospectively identified discordant cases; matched ascertainment and independent replication.
Competing explanation: Attention, mood and working memory may differ in sensitivity and recovery.
Discriminating test: Longer controlled exposure/reduction studies with prespecified domains, washout and repeated brain measures; distinguish early-treated adults from developmental injury.
Competing explanation: Transport competition, monoamine inhibition and developmental structural effects may have different roles.
Discriminating test: Age-stratified model blockade/rescue and human mediator measurement; require outcomes beyond blood phenylalanine and avoid attributing every effect to one pathway.
Competing explanation: A biochemical response may leave previous damage or adherence-related fluctuations unchanged.
Discriminating test: Prospective comparative follow-up with cognition, function, exposure variability and adverse events; separate responder-enriched maintenance from initiation trials.
Electronic publication dates are used where recorded, with issue years shown separately. This is a selected chronology, not a claim of scientific priority or independent replication for every entry.
An early report examined phenylalanine intake in PKU.
What it cannot establish: Metadata-only historical anchor: outcome details were not independently re-examined in this update.
Earlier treatment was associated with better intellectual outcomes.
What it cannot establish: Nonrandomized developmental treatment comparison; family and timing factors require attention.
Brain transport varied among patients with different clinical vulnerability.
What it cannot establish: Small selected sample does not explain all preserved untreated cognition.
Other large neutral amino acids blocked brain phenylalanine influx and EEG slowing.
What it cannot establish: Acute transport and EEG effects do not establish long-term cognitive recovery.
Responsive patients had lower blood phenylalanine on treatment.
What it cannot establish: Blood lowering is not itself a hard neurocognitive outcome.
Higher phenylalanine impaired sustained attention and mood in the tested adults.
What it cannot establish: Short challenge in early-treated adults does not measure irreversible childhood injury.
Blood lowering corrected monoamine deficits and partly improved behaviour.
What it cannot establish: Adult biochemical rescue did not reverse all developmental cognitive deficits.
Continuation maintained lower blood phenylalanine than discontinuation.
What it cannot establish: An enriched withdrawal design tests maintenance, not untreated developmental causation.
Working-memory accuracy met the noninferiority criterion, while sustained attention differed.
What it cannot establish: Domain-specific and short-term outcomes do not justify a general claim that high phenylalanine is harmless.
Sisters had strikingly different cognitive outcomes despite similar tested biochemical/genetic features.
What it cannot establish: A rare discordant pair identifies an unresolved modifier rather than reversing population-level causation.
Case-specific Consensus records assisted gap discovery, chronology and targeted paper questions. Shared template wording about an amyloid-specific Deep follow-up is not evidence of a Deep run for this topic; the dated source records establish the actual use and access limits. Primary identifiers, selected abstract passages, correction notices and available primary-body passages were cross-checked. Generated absence cells, duplicate milestones and unsupported access claims were rejected.
Results: washout was at least four weeks and phenylalanine approached baseline before the second period. Adult challenge outcomes do not test fixed childhood injury.
This focused addendum does not establish 50–70 complete primary Methods/Results examinations per review. Baseline reading receipts and scores retain their original scope.
Selected full-text checks: 1; abstract checks: 8; metadata-only anchors: 1. Complete-paper examinations credited in this update: 0.
New enrichment: HSEF v5.3 causal distinctions. Archived scorecard schema: 5.4; retained as recorded.
PMID 13098090 · DOI 10.1016/s0140-6736(53)90473-5
Metadata only: historical anchor. Identifier, title and publication metadata checked; original results not re-examined.
PMID 4140266 · DOI 10.1016/s0140-6736(74)91873-x
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
PMID 9809507 · DOI 10.1097/00004647-199811000-00004
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
PMID 10207169 · DOI 10.1172/JCI5017
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
PMID 17693179 · DOI 10.1016/S0140-6736(07)61234-3
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
PMID 21153445 · DOI 10.1007/s10545-010-9253-9
Selected full-text passages checked. Results: washout was at least four weeks and phenylalanine approached baseline before the second period. Adult challenge outcomes do not test fixed childhood injury.
PMID 29331172 · DOI 10.1016/j.ymgme.2017.10.009
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
PMID 29628378 · DOI 10.1016/j.ymgme.2018.03.003
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
PMID 38569786 · DOI 10.1016/j.ajcnut.2023.11.007
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
PMID 41853686 · DOI 10.1016/j.ymgmr.2026.101304
Selected abstract passages checked. Primary record and selected abstract passages checked; no complete-paper appraisal credited.
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