In muscle cytochrome oxidase (COX) negative fibers (mitochondrial mosaics) have often been visualized.

A phenylalanine-restricted diet, supplemented with protein substitutes (PSs), remains the cornerstone of phenylketonuria (PKU) management. However, adherence is challenging in adulthood, and data on the nutritional status of early and continuously treated adults with PKU (ETAwPKU) are scarce. A total of 34 ETAwPKU (16 females; mean ± SD, age: 28 ± 9 years, phenylalanine concentration: 847 ± 285 µmol/L) and 34 age- and sex-matched control subjects were compared regarding their blood nutrient status, self-reported dietary intake, and cognitive wellbeing. Though diet adherence varied, all ETAwPKU were taking a PS. No significant differences were found for blood DHA, calcium, ferritin, transferrin, and zinc concentrations. However, selenium and ubiquinone concentrations were 16% and 29% lower in ETAwPKU, respectively (p < 0.01 and <0.0001). Vitamin concentrations (D, B12, B6, and folic acid) were significantly higher in ETAwPKU except for alpha-tocopherol. Amino acid (AA) concentrations differed between ETAwPKU and controls: they were significantly lower for 12 AAs and higher for phenylalanine and glycine. ETAwPKU had a significantly higher intake of most minerals and vitamins, except for niacin and phosphorus (no difference). Depending on the nutrient, PSs represented 52–100% of patients’ daily intake and 19% of total daily energy intake. Compared with controls, ETAwPKU scored significantly lower in three of the four subscales of the cognitive wellbeing questionnaire. Overall, the blood DHA and micronutrient status of ETAwPKU was adequate, except for selenium, with higher intakes than controls for most micronutrients. Patients relied heavily on PSs to meet the recommended intakes for protein, DHA, and micronutrients. The potential clinical impact of differences found in AA status should be further studied.

Acute neonatal hyperammonemia is associated with poor neurological outcomes and high mortality. We developed, based on kinetic modeling, a user-friendly and widely applicable algorithm to tailor the treatment of acute neonatal hyperammonemia. A single compartmental model was calibrated assuming a distribution volume equal to the patient’s total body water (V), as calculated using Wells’ formula, and dialyzer clearance as derived from the measured ammonia time–concentration curves during 11 dialysis sessions in four patients (3.2 ± 0.4 kg). Based on these kinetic simulations, dialysis protocols could be derived for clinical use with different body weights, start concentrations, dialysis machines/dialyzers and dialysis settings (e.g., blood flow Q_B). By a single measurement of ammonia concentration at the dialyzer inlet and outlet, dialyzer clearance (K) can be calculated as K = Q_B∙[(C_inlet − C_outlet)/C_inlet]. The time (T) needed to decrease the ammonia concentration from a predialysis start concentration C_start to a desired target concentration C_target is then equal to T = (−V/K)∙LN(C_target/C_start). By implementing these formulae in a simple spreadsheet, medical staff can draw an institution-specific flowchart for patient-tailored treatment of hyperammonemia.

Pyridoxine-dependent epilepsy (PDE) represents a group of rare developmental and epileptic encephalopathies. The most common PDE is caused by biallelic pathogenic variants in ALDH7A1 (PDE-ALDH7A1; OMIM #266100), which encodes α-aminoadipate semialdehyde (α-AASA) dehydrogenase, a key enzyme in lysine catabolism. Affected individuals present with seizures unresponsive to conventional anticonvulsant medications but responsive to high-dose of pyridoxine (vitamin B6). Adjunctive lysine restriction and arginine supplementation have also shown potential in improving neurodevelopmental outcomes. Given the significant benefit of early intervention, PDE-ALDH7A1 is a strong candidate for newborn screening (NBS). However, traditional biomarkers are biochemically unstable at room temperature (α-AASA and piperideine-6-carboxylate) or lack sufficient specificity (pipecolate), limiting their utility for biomarker-based NBS. The recent identification of two novel and stable biomarkers, 2S,6S-/2S,6R-oxopropylpiperidine-2-carboxylate (2-OPP) and 6-oxo-pipecolate (oxo-PIP), offers renewed potential for biochemical NBS. We evaluated the feasibility of incorporating 2-OPP, oxo-PIP, and pipecolate into routine butylated FIA-MS/MS workflows used for biochemical NBS. A total of 9402 dried blood spots (DBS), including nine confirmed PDE-ALDH7A1 patients and 9393 anonymized controls were analyzed using a single multiplex assay. 2-OPP emerged as the most sensitive biomarker, identifying all PDE-ALDH7A1 patients with 100% sensitivity and a positive predictive value (PPV) of 18.4% using a threshold above the 99.5th percentile. Combining elevated 2-OPP (above the 99.5th percentile) with either pipecolate or oxo-PIP (above the 85.0th percentile) as secondary marker detected within the same multiplex FIA-MS/MS assay further improved the PPVs to 60% and 45%, respectively, while maintaining compatibility with butanol-derivatized method. Notably, increasing the 2-OPP threshold above the 99.89th percentile, in combination with either pipecolate or oxo-PIP above the 85.0th percentile resulted in both 100% sensitivity and 100% PPV. This study supports the strong potential of 2-OPP-based neonatal screening for PDE-ALDH7A1 within existing NBS infrastructures. The ability to multiplex 2-OPP, pipecolate and oxo-PIP within a single assay offers a robust, practical, high-throughput and cost-effective approach. These results support the inclusion of PDE-ALDH7A1 in existing biochemical NBS panels. Further prospective studies in larger cohorts are needed to refine cutoffs and confirm clinical performance.