Phenylketonuria (PKU) is often considered as the classical example of a genetic disorder in which severe symptoms can nowadays successfully be prevented by early diagnosis and treatment. In contrast, untreated or late-treated PKU is known to result in severe intellectual disability, seizures, and behavioral disturbances. Rarely, however, untreated or late-diagnosed PKU patients with high plasma phenylalanine concentrations have been reported to escape from intellectual disability. The present study aimed to review published cases of such PKU patients. To this purpose, we conducted a literature search in PubMed and EMBASE up to 8th of September 2017 to identify cases with 1) PKU diagnosis and start of treatment after 7 years of age; 2) untreated plasma phenylalanine concentrations ≥1200 μmol/l; and 3) IQ ≥80. Literature search, checking reference lists, selection of articles, and extraction of data were performed by two independent researchers. In total, we identified 59 published cases of patients with late-diagnosed PKU and unexpected favorable outcome who met the inclusion criteria. Although all investigated patients had intellectual functioning within the normal range, at least 19 showed other neurological, psychological, and/or behavioral symptoms. Based on the present findings, the classical symptomatology of untreated or late-treated PKU may need to be rewritten, not only in the sense that intellectual dysfunction is not obligatory, but also in the sense that intellectual functioning does not (re)present the full picture of brain damage due to high plasma phenylalanine concentrations. Further identification of such patients and additional analyses are necessary to better understand these differences between PKU patients.

We aimed to assess the current state of PKU screening and management in the region of southeastern Europe. A survey was performed involving all identified professionals responsible for the PKU management in the 11 countries from South-Eastern region of Europe (Albania, Bulgaria, Bosnia and Herzegovina, Croatia, Kosovo, Macedonia, Moldova, Montenegro, Romania, Serbia, Slovenia). The questionnaire was designed to assess the characteristics regarding PKU management in three main areas: nation-wide characteristics, PKU screening, and characteristics of the PKU management in the responding centre. It consisted of 56 questions. The distribution and collection of the questionnaires (via e-mail) was taking place from December 2013 to March 2014. Responses from participants from 11 countries were included; the countries cumulative population is approx. 52.5 mio. PKU screening was not yet introduced in 4 of 11 countries. Reported PKU incidences ranged from 1/7325 to 1/39338 (and were not known for 5 countries). National PKU guidelines existed in 5 of 11 countries and 7 of 11 countries had PKU registry (registries included 40 to 194 patients). The number of PKU centers in each country varied from 1 to 6. Routine genetic diagnostics was reported in 4 of 11 countries. Most commonly used laboratory method to assess phenylalanine levels was fluorometric. Tetrahydrobiopterine was used in only 2 of 11 countries. Most frequently, pediatricians were caring for the patients. Dietitian was a member of PKU team in only 4 of 11 countries, while regular psychological assessments were performed in 6 of 11 countries. Patient’s PKU society existed in 7 of 11 countries. The region of southeastern Europe was facing certain important challenges of PKU screening and management. Neonatal PKU screening should be introduced throughout the region. Furthermore, PKU management was falling behind internationally established standards-of-care in many aspects.

Phenylketonuria (PKU) management is aimed at preventing neurocognitive and psychosocial dysfunction by keeping plasma phenylalanine concentrations within the recommended target range. It can be questioned, however, whether universal plasma phenylalanine target levels would result in optimal neurocognitive outcomes for all patients, as similar plasma phenylalanine concentrations do not seem to have the same consequences to the brain for each PKU individual. To better understand the inter-individual differences in brain vulnerability to high plasma phenylalanine concentrations, we aimed to identify untreated and/or late-diagnosed PKU patients with near-normal outcome, despite high plasma phenylalanine concentrations, who are still alive. In total, we identified 16 such cases. While intellectual functioning in these patients was relatively unaffected, they often did present other neurological, psychological, and behavioral problems. Thereby, these “unusual” PKU patients show that the classical symptomatology of untreated or late-treated PKU may have to be rewritten. Moreover, these cases show that a lack of intellectual dysfunction despite high plasma phenylalanine concentrations does not necessarily imply that these high phenylalanine concentrations have not been toxic to the brain. Also, these cases may suggest that different mechanisms are involved in PKU pathophysiology, of which the relative importance seems to differ between patients and possibly also with increasing age. Further research should aim to better distinguish PKU patients with respect to their cerebral effects to high plasma phenylalanine concentrations.

Phenylketonuria (PKU) is caused by mutations in the gene encoding phenylalanine hydroxylase (PAH) enzyme. Here, we report the updated spectrum of PAH mutations in 61 Serbian PKU patients. By using both DGGE/DNA sequencing and PCR-RFLP, we identified 26 disease-causing mutations (detection rate 99%). The most frequent ones were p.L48S (31%), p.R408W (16.4%), p.P281L (6%), p.E390G (5.2%), and p.I306V (5.2%). Homozygosity value indicated high heterogeneity of Serbian population. To overcome possible pitfalls of patients’ phenotypic classification, we used two parameters: pretreatment/maximal phenylalanine blood concentration and Phe tolerance. The two phenotypes did not match only for patients with p.L48S. Therefore, we used Mann-Whitney statistical test to compare pretreatment/maximal blood Phe concentration and Phe tolerance detected in patients with p.[L48S];[null] and p.[missense];[null] genotypes. For patients with p.L48S, our results implied that Phe tolerance is a better parameter for phenotypic classification. Also, Fisher’s exact test was used to compare p.L48S effect on phenotype of homozygous and functionally hemizygous patients. Our findings showed that effect of p.L48S was altered in functional hemizygotes. Moreover, phenotypic inconsistency found in homozygotes suggested that interallelic complementation and/or additional factors play a role in genotype-phenotype correlation. Since BH4-supplementation therapy is not available in Serbia, we made the first estimation of its potential benefit based on patients’ genotypes. In the analyzed cohort, the total frequency of BH4-responsive mutations was 52.6%. Furthermore, we found a significant number of genotypes (26.2% BH4-responsive and 51% probably BH4-responsive) that may respond to BH4 therapy. This led us to a conclusion that BH4-supplementation therapy could bring benefit to Serbian PKU patients.

Background Childhood epilepsies are caused by heterogeneous underlying disorders where approximately 40% of the origins of epilepsy can be attributed to genetic factors. The application of next-generation sequencing (NGS) has revolutionized molecular diagnostics and has enabled the identification of disease-causing genes and variants in childhood epilepsies. The objective of this study was to use NGS to identify variants in patients with childhood epilepsy, to expand the variant spectrum and discover potential therapeutic targets. Methods In our study, 55 children with epilepsy of unknown etiology were analyzed by combining clinical-exome and whole-exome sequencing. Novel variants were characterized using various in silico algorithms for pathogenicity and structure prediction. Results The molecular genetic cause of epilepsy was identified in 28 patients and the overall diagnostic success rate was 50.9%. We identified variants in 22 different genes associated with epilepsy that correlate well with the described phenotype. SCN1A gene variants were found in five unrelated patients, while ALDH7A1 and KCNQ2 gene variants were found twice. In the other 19 genes, variants were found only in a single patient. This includes genes such as ASH1L, CSNK2B, RHOBTB2, and SLC13A5, which have only recently been associated with epilepsy. Almost half of diagnosed patients (46.4%) carried novel variants. Interestingly, we identified variants in ALDH7A1, KCNQ2, PNPO, SCN1A, and SCN2A resulting in gene-directed therapy decisions for 11 children from our study, including four children who all carried novel SCN1A genetic variants. Conclusions Described novel variants will contribute to a better understanding of the European genetic landscape, while insights into the genotype-phenotype correlation will contribute to a better understanding of childhood epilepsies worldwide. Given the expansion of molecular-based approaches, each newly identified genetic variant could become a potential therapeutic target.