Browsing by Author "Klaassen, Kristel (54959837700)"

Background: Phenylketonuria (PKU) is a metabolic disorder caused by phenylalanine hydroxylase gene (PAH) mutations. If left untreated, PKU patients develop severe mental retardation potentially due to neurodegeneration. This is the first study that investigates presence of mitochondrial DNA variants in PKU patients, m.10398A, reportedly associated with neurodegenerative diseases and m.10410T. Methods: We analyzed 64 PKU patients and 50 healthy controls from Serbian population. PKU patients were categorized into groups according to time of diagnosis and compliance to low-phenylalanine diet. The IQ was determined according to age-appropriate scales. Results: We detected m.10398A and m.10410T variants by direct sequencing. Frequency of m.10398A was similar in patients and healthy controls (82.81% and 82.00% respectively) suggesting their identical ethnic background. No variation was detected for m.10410. In group with late diagnosis and poorly controlled diet, no statistically significant difference in average IQ was found between patients with m.10398A and m.10398G. The same was shown for PKU patients with higher IQ, diagnosed at neonatal screening and treated with low-phenylalanine diet. However, when patients carrying p.L48S, a PAH mutation with inconsistent effect, were excluded from the study, presence of m.10398A variant was associated with lower IQ. Conclusions: This study emphasizes the importance of neonatal screening and good control of low-phenylalanine diet in PKU patients. Statistical analysis did not indicate clear impact of mitochondrial DNA variant m.10398A on IQ of PKU patients, except when PAH genotype was also considered. Studies in larger cohorts will elucidate the association between PAH gene mutations, mitochondrial DNA variants and complex PKU cognitive phenotype.

Background: Phenylketonuria (PKU) is a metabolic disorder caused by phenylalanine hydroxylase gene (PAH) mutations. If left untreated, PKU patients develop severe mental retardation potentially due to neurodegeneration. This is the first study that investigates presence of mitochondrial DNA variants in PKU patients, m.10398A, reportedly associated with neurodegenerative diseases and m.10410T. Methods: We analyzed 64 PKU patients and 50 healthy controls from Serbian population. PKU patients were categorized into groups according to time of diagnosis and compliance to low-phenylalanine diet. The IQ was determined according to age-appropriate scales. Results: We detected m.10398A and m.10410T variants by direct sequencing. Frequency of m.10398A was similar in patients and healthy controls (82.81% and 82.00% respectively) suggesting their identical ethnic background. No variation was detected for m.10410. In group with late diagnosis and poorly controlled diet, no statistically significant difference in average IQ was found between patients with m.10398A and m.10398G. The same was shown for PKU patients with higher IQ, diagnosed at neonatal screening and treated with low-phenylalanine diet. However, when patients carrying p.L48S, a PAH mutation with inconsistent effect, were excluded from the study, presence of m.10398A variant was associated with lower IQ. Conclusions: This study emphasizes the importance of neonatal screening and good control of low-phenylalanine diet in PKU patients. Statistical analysis did not indicate clear impact of mitochondrial DNA variant m.10398A on IQ of PKU patients, except when PAH genotype was also considered. Studies in larger cohorts will elucidate the association between PAH gene mutations, mitochondrial DNA variants and complex PKU cognitive phenotype.

Background: COVID-19 pandemic has proved to be an unrelenting health threat for more than a year now. The emerging amount of data indicates that vitamin D, zinc and selenium could be important for clinical presentation of COVID-19. Here, we investigated association of genetic variants related to the altered level and bioavailability of vitamin D, zinc and selenium with clinical severity of COVID-19. Methods: We analyzed variants in genes significant for the status of vitamin D (DHCR7/NADSYN1 rs12785878, GC rs2282679, CYP2R1 rs10741657, and VDR rs2228570), zinc (PPCDC rs2120019) and selenium (DMGDH rs17823744) in 120 Serbian adult and pediatric COVID-19 patients using allelic discrimination. Furthermore, we carried out comparative population genetic analysis among European and other worldwide populations to investigate variation in allelic frequencies of selected variants. Results: Study showed that DHCR7/NADSYN rs12785878 and CYP2R1 rs10741657 variants were associated with severe COVID-19 in adults (p = 0.03, p = 0.017, respectively); carriers of DHCR7/NADSYN TG+GG and CYP2R1 GG genotypes had 0.21 and 5.9 the odds for developing severe disease, OR 0.21 (0.05–0.9) and OR 5.9 (1.4–25.2), respectively. There were no associations between selected genetic variants and disease severity in pediatric patients. Comparative population genetic analysis revealed that Serbian population had the lowest frequency of CYP2R1 rs10741657 G allele compared to other non-Finish Europeans (0.58 compared to 0.69 and 0.66 in Spanish and Italian population, respectively), suggesting that other populations should also investigate the relationship of CYP2R1 variant and the COVID-19 disease course. Conclusion: The results of the study indicated that vitamin D related genetic variants were implicated in severe COVID-19 in adults. This could direct prevention strategies based on population specific nutrigenetic profiles. © Copyright © 2021 Kotur, Skakic, Klaassen, Gasic, Zukic, Skodric-Trifunovic, Stjepanovic, Zivkovic, Ostojic, Stevanovic, Lavadinovic, Pavlovic and Stankovic.

Background: COVID-19 pandemic has proved to be an unrelenting health threat for more than a year now. The emerging amount of data indicates that vitamin D, zinc and selenium could be important for clinical presentation of COVID-19. Here, we investigated association of genetic variants related to the altered level and bioavailability of vitamin D, zinc and selenium with clinical severity of COVID-19. Methods: We analyzed variants in genes significant for the status of vitamin D (DHCR7/NADSYN1 rs12785878, GC rs2282679, CYP2R1 rs10741657, and VDR rs2228570), zinc (PPCDC rs2120019) and selenium (DMGDH rs17823744) in 120 Serbian adult and pediatric COVID-19 patients using allelic discrimination. Furthermore, we carried out comparative population genetic analysis among European and other worldwide populations to investigate variation in allelic frequencies of selected variants. Results: Study showed that DHCR7/NADSYN rs12785878 and CYP2R1 rs10741657 variants were associated with severe COVID-19 in adults (p = 0.03, p = 0.017, respectively); carriers of DHCR7/NADSYN TG+GG and CYP2R1 GG genotypes had 0.21 and 5.9 the odds for developing severe disease, OR 0.21 (0.05–0.9) and OR 5.9 (1.4–25.2), respectively. There were no associations between selected genetic variants and disease severity in pediatric patients. Comparative population genetic analysis revealed that Serbian population had the lowest frequency of CYP2R1 rs10741657 G allele compared to other non-Finish Europeans (0.58 compared to 0.69 and 0.66 in Spanish and Italian population, respectively), suggesting that other populations should also investigate the relationship of CYP2R1 variant and the COVID-19 disease course. Conclusion: The results of the study indicated that vitamin D related genetic variants were implicated in severe COVID-19 in adults. This could direct prevention strategies based on population specific nutrigenetic profiles. © Copyright © 2021 Kotur, Skakic, Klaassen, Gasic, Zukic, Skodric-Trifunovic, Stjepanovic, Zivkovic, Ostojic, Stevanovic, Lavadinovic, Pavlovic and Stankovic.

Introduction: PU.1-mutated agammaglobulinemia (PU.MA) represents a recently described autosomal-dominant form of agammaglobulinemia caused by mutation of the SPI1 gene. This gene codes for PU.1 pioneer transcription factor important for the maturation of monocytes, B lymphocytes, and conventional dendritic cells. Only six cases with PU.MA, presenting with chronic sinopulmonary and systemic enteroviral infections, have been previously described. Accumulating literature evidence suggests a possible relationship between SPI1 mutation, microglial phagocytic dysfunction, and the development of Alzheimer’s disease (AD). Case description: We present a Caucasian female patient born from a non-consanguineous marriage, who was diagnosed with agammaglobulinemia at the age of 15 years when the immunoglobulin replacement therapy was started. During the following seventeen years, she was treated for recurrent respiratory and intestinal infections. At the age of 33 years, the diagnosis of celiac-like disease was established. Five years later progressive cognitive deterioration, unstable gait, speech disturbances, and behavioral changes developed. Comprehensive microbiological investigations were negative, excluding possible infective etiology. Brain MRI, 18FDG-PET-CT, and neuropsychological testing were suggestive for a diagnosis of a frontal variant of AD. Clinical exome sequencing revealed the presence of a novel frameshift heterozygous variant c.441dup in exon 4 of the SPI1 gene. Despite intensive therapy, the patient passed away a few months after the onset of the first neurological symptoms. Conclusion: We describe the first case of PU.MA patient presenting with a rapidly progressive neurocognitive deterioration. The possible role of microglial dysfunction in patients with SPI1 mutation could explain their susceptibility to neurodegenerative diseases thus highlighting the importance of genetic testing in patients with inborn errors of immunity. Since PU.MA represents a newly described form of agammaglobulinemia, our case expands the spectrum of manifestations associated with SPI1 mutation. Copyright © 2024 Miskovic, Ljubicic, Bonaci-Nikolic, Petkovic, Markovic, Rankovic, Djordjevic, Stankovic, Klaassen, Pavlovic and Stojanovic.

Introduction: PU.1-mutated agammaglobulinemia (PU.MA) represents a recently described autosomal-dominant form of agammaglobulinemia caused by mutation of the SPI1 gene. This gene codes for PU.1 pioneer transcription factor important for the maturation of monocytes, B lymphocytes, and conventional dendritic cells. Only six cases with PU.MA, presenting with chronic sinopulmonary and systemic enteroviral infections, have been previously described. Accumulating literature evidence suggests a possible relationship between SPI1 mutation, microglial phagocytic dysfunction, and the development of Alzheimer’s disease (AD). Case description: We present a Caucasian female patient born from a non-consanguineous marriage, who was diagnosed with agammaglobulinemia at the age of 15 years when the immunoglobulin replacement therapy was started. During the following seventeen years, she was treated for recurrent respiratory and intestinal infections. At the age of 33 years, the diagnosis of celiac-like disease was established. Five years later progressive cognitive deterioration, unstable gait, speech disturbances, and behavioral changes developed. Comprehensive microbiological investigations were negative, excluding possible infective etiology. Brain MRI, 18FDG-PET-CT, and neuropsychological testing were suggestive for a diagnosis of a frontal variant of AD. Clinical exome sequencing revealed the presence of a novel frameshift heterozygous variant c.441dup in exon 4 of the SPI1 gene. Despite intensive therapy, the patient passed away a few months after the onset of the first neurological symptoms. Conclusion: We describe the first case of PU.MA patient presenting with a rapidly progressive neurocognitive deterioration. The possible role of microglial dysfunction in patients with SPI1 mutation could explain their susceptibility to neurodegenerative diseases thus highlighting the importance of genetic testing in patients with inborn errors of immunity. Since PU.MA represents a newly described form of agammaglobulinemia, our case expands the spectrum of manifestations associated with SPI1 mutation. Copyright © 2024 Miskovic, Ljubicic, Bonaci-Nikolic, Petkovic, Markovic, Rankovic, Djordjevic, Stankovic, Klaassen, Pavlovic and Stojanovic.

Background: Crohn's disease (CD) is chronic inflammatory bowel disease with different phenotypic characteristics influencing disease prognosis and therapeutic strategies. The aim of this pilot study was to analyze selected inflammatory and apoptotic markers in non-inflamed and inflamed samples of ileal mucosa of non-stricturing/non-penetrating (NS/NP) and stricturing (S) CD mucosal phenotypes in order to characterize their distinct profiles. Methods: From twenty CD patients (9 NS/NP, 11 S) paired non-inflamed and inflamed ileal biopsies were collected and used for analysis of cytokine (TNF and IL6) and apoptotic (Bcl2, Bax, Fas and FasL) genes' expression levels by real-time PCR, while NFκB transcriptional potency was assessed by electromobility gel shift assay. Results: Our results demonstrated significant upregulation of TNF and IL6 in inflamed area of both NS/NP (p = 0.03, p = 0.01) and S phenotypes (p = 0.04, p = 0.04), respectively. However, TNF increase was more prominent in NS/NP compared to S inflamed mucosa (p = 0.02). Also, level of proapoptotic Bax was significantly higher in NS/NP compared to S inflamed mucosa (p = 0.01). Opposing transcription potency of NFκB has been detected between two phenotypes: being decreased in NS/NP (p = 0.07) and increased in S (p = 0.1) inflamed compared to non-inflamed mucosa, demonstrating trend towards statistical significance. Conclusions: We found that two distinct CD phenotypes have specific molecular signatures. Obtained results could direct improvement of current and development of new therapeutic strategies based on more specific molecular stratification of CD patients. © 2020 Elsevier GmbH

Background: Crohn's disease (CD) is chronic inflammatory bowel disease with different phenotypic characteristics influencing disease prognosis and therapeutic strategies. The aim of this pilot study was to analyze selected inflammatory and apoptotic markers in non-inflamed and inflamed samples of ileal mucosa of non-stricturing/non-penetrating (NS/NP) and stricturing (S) CD mucosal phenotypes in order to characterize their distinct profiles. Methods: From twenty CD patients (9 NS/NP, 11 S) paired non-inflamed and inflamed ileal biopsies were collected and used for analysis of cytokine (TNF and IL6) and apoptotic (Bcl2, Bax, Fas and FasL) genes' expression levels by real-time PCR, while NFκB transcriptional potency was assessed by electromobility gel shift assay. Results: Our results demonstrated significant upregulation of TNF and IL6 in inflamed area of both NS/NP (p = 0.03, p = 0.01) and S phenotypes (p = 0.04, p = 0.04), respectively. However, TNF increase was more prominent in NS/NP compared to S inflamed mucosa (p = 0.02). Also, level of proapoptotic Bax was significantly higher in NS/NP compared to S inflamed mucosa (p = 0.01). Opposing transcription potency of NFκB has been detected between two phenotypes: being decreased in NS/NP (p = 0.07) and increased in S (p = 0.1) inflamed compared to non-inflamed mucosa, demonstrating trend towards statistical significance. Conclusions: We found that two distinct CD phenotypes have specific molecular signatures. Obtained results could direct improvement of current and development of new therapeutic strategies based on more specific molecular stratification of CD patients. © 2020 Elsevier GmbH

Hereditary persistence of fetal hemoglobin (HPFH) is a condition characterized by persistent γ-globin gene expression and synthesis of high levels of fetal hemoglobin (Hb F; α2γ2) during adult life. It is usually caused by promoter variants or large deletions affecting the human fetal globin (HBG1 and HBG2) genes. Some of these HPFH-causing variants, such as HBG2: g.-158 C > T, exert their effect only under conditions of erythropoietic stress, typical for β-thalassemia (β-thal) patients. Namely, the presence of HBG2: g.-158 C > T favors a higher Hb F response, while it has little effect in healthy individuals. We analyzed a previously reported deletion residing in the promoter region of the HBG1 gene (HBG1: g.-225-222delAGCA), both in normal conditions and under conditions of erythropoietic stress. Our results indicate that this deletion is responsible for decreased HBG1 gene expression. Specifically, this deletion was shown to result in drastically reduced reporter gene expression in K562 cells, compared to the wild-type sequence but only under conditions of erythropoietic stress, mimicked by introduction of erythropoietin (EPO) into the cell culture. Also, electrophoretic mobility shift analysis showed that the HBG1: g.-225-222delAGCA deletion creates additional transcriptional factors binding sites, which, we propose, bind a transcriptional repressor, thus decreasing the HBG1 gene promoter activity. These results are consistent with in silico analysis, which indicated that this deletion creates a binding site for GATA1, known to be a repressor of the γ-globin gene expression. These data confirm the regulatory role of the HBG1: g.-225-222 region that exerts its effect under conditions of erythropoietic stress characteristic for β-thal patients. © 2015 Taylor & Francis.

Hereditary persistence of fetal hemoglobin (HPFH) is a condition characterized by persistent γ-globin gene expression and synthesis of high levels of fetal hemoglobin (Hb F; α2γ2) during adult life. It is usually caused by promoter variants or large deletions affecting the human fetal globin (HBG1 and HBG2) genes. Some of these HPFH-causing variants, such as HBG2: g.-158 C > T, exert their effect only under conditions of erythropoietic stress, typical for β-thalassemia (β-thal) patients. Namely, the presence of HBG2: g.-158 C > T favors a higher Hb F response, while it has little effect in healthy individuals. We analyzed a previously reported deletion residing in the promoter region of the HBG1 gene (HBG1: g.-225-222delAGCA), both in normal conditions and under conditions of erythropoietic stress. Our results indicate that this deletion is responsible for decreased HBG1 gene expression. Specifically, this deletion was shown to result in drastically reduced reporter gene expression in K562 cells, compared to the wild-type sequence but only under conditions of erythropoietic stress, mimicked by introduction of erythropoietin (EPO) into the cell culture. Also, electrophoretic mobility shift analysis showed that the HBG1: g.-225-222delAGCA deletion creates additional transcriptional factors binding sites, which, we propose, bind a transcriptional repressor, thus decreasing the HBG1 gene promoter activity. These results are consistent with in silico analysis, which indicated that this deletion creates a binding site for GATA1, known to be a repressor of the γ-globin gene expression. These data confirm the regulatory role of the HBG1: g.-225-222 region that exerts its effect under conditions of erythropoietic stress characteristic for β-thal patients. © 2015 Taylor & Francis.

Background and aims: Mucosal gene expression have not been fully enlightened in inflammatory bowel disease (IBD). Aim of this study was to define IL23A, IL17A, IL17F and TLR9 expression in different IBD phenotypes. Methods: Evaluation of mRNA levels was performed in paired non-inflamed and inflamed mucosal biopsies of newly diagnosed 50 Crohn's disease (CD) and 54 ulcerative colitis (UC) patients by quantitative real-time PCR analysis. Results: IL17A and IL17F expression levels were significantly increased in inflamed IBD mucosa. Inflamed CD ileal and UC mucosa showed increased IL23A, while only inflamed CD ileal samples showed increased TLR9 mRNA level. Correlation between analysed mRNAs levels and endoscopic and clinical disease activity were found in UC, but only with clinical activity in CD. Conclusion: Both CD and UC presented expression of Th17-associated genes. Nevertheless, expression profiles between different disease forms varies which should be taken into account for future research and therapeutics strategies. © 2018 Elsevier Inc.

Background and aims: Mucosal gene expression have not been fully enlightened in inflammatory bowel disease (IBD). Aim of this study was to define IL23A, IL17A, IL17F and TLR9 expression in different IBD phenotypes. Methods: Evaluation of mRNA levels was performed in paired non-inflamed and inflamed mucosal biopsies of newly diagnosed 50 Crohn's disease (CD) and 54 ulcerative colitis (UC) patients by quantitative real-time PCR analysis. Results: IL17A and IL17F expression levels were significantly increased in inflamed IBD mucosa. Inflamed CD ileal and UC mucosa showed increased IL23A, while only inflamed CD ileal samples showed increased TLR9 mRNA level. Correlation between analysed mRNAs levels and endoscopic and clinical disease activity were found in UC, but only with clinical activity in CD. Conclusion: Both CD and UC presented expression of Th17-associated genes. Nevertheless, expression profiles between different disease forms varies which should be taken into account for future research and therapeutics strategies. © 2018 Elsevier Inc.

Background: The study was undertaken to assess the influence of functional-308G/A TNF-α (rs 1800629) and-174G/C IL-6 (rs1800795) promoter polymorphisms on the therapeutic response to etanercept, a TNF-α blocker, in patients with rheumatoid arthritis (RA). Methods: Seventy-three patients suffering from active RA were studied, at baseline and 6 and 12 months after therapy. The therapeutic response was estimated according to the European League Against Rheumatism response criteria. Patients were genotyped for-308G/A TNF-α and-174G/C IL-6 polymorphisms by the PCR-RFLP method, and the influence of genotype on etanercept response was assessed. Results: No difference in the percentage of responders (patients who had DAS28 improvement > 1.2) between patients with the TNF-α-308GG and GA and AA genotype was detected after 6 and 12 months of treatment. After 12 months of treatment the percentage of responders was significantly increased in patients with the IL-6-174GG genotype compared with those with the GC or CC genotype (p=0.006 by Chi-square test). Evaluation of the patients according to their combined IL-6/TNF-α genotypes showed that patients with the IL-6-174GG/TNF-α-308GG genotype were more frequent among the responders compared to those with other combined genotypes (p=0.022 by Chisquare test). More precisely, all patients with the combined IL-6-174GG/TNF-α-308GG genotype were responders after 12 months of etanercept treatment. Conclusions: The study suggests that patients who are genetically low TNF-α and IL-6 producers are the best responders to etanercept therapy.

Background: The study was undertaken to assess the influence of functional-308G/A TNF-α (rs 1800629) and-174G/C IL-6 (rs1800795) promoter polymorphisms on the therapeutic response to etanercept, a TNF-α blocker, in patients with rheumatoid arthritis (RA). Methods: Seventy-three patients suffering from active RA were studied, at baseline and 6 and 12 months after therapy. The therapeutic response was estimated according to the European League Against Rheumatism response criteria. Patients were genotyped for-308G/A TNF-α and-174G/C IL-6 polymorphisms by the PCR-RFLP method, and the influence of genotype on etanercept response was assessed. Results: No difference in the percentage of responders (patients who had DAS28 improvement > 1.2) between patients with the TNF-α-308GG and GA and AA genotype was detected after 6 and 12 months of treatment. After 12 months of treatment the percentage of responders was significantly increased in patients with the IL-6-174GG genotype compared with those with the GC or CC genotype (p=0.006 by Chi-square test). Evaluation of the patients according to their combined IL-6/TNF-α genotypes showed that patients with the IL-6-174GG/TNF-α-308GG genotype were more frequent among the responders compared to those with other combined genotypes (p=0.022 by Chisquare test). More precisely, all patients with the combined IL-6-174GG/TNF-α-308GG genotype were responders after 12 months of etanercept treatment. Conclusions: The study suggests that patients who are genetically low TNF-α and IL-6 producers are the best responders to etanercept therapy.

Background: This study analyzed poorly understood relationship of two overlapping conditions: metabolic syndrome (MeS) and inflammatory bowel disease (IBD), both associated with inflammation in the visceral adipose tissue. Methods: Newly diagnosed 104 IBD patients, of which 50 Crohn's disease (CD) and 54 ulcerative colitis (UC), and 45 non-IBD controls were examined for MeS-related obesity and lipid markers. Th-17 immune genes IL17A, IL17F, IL23A, and TLR9 mRNAs were measured in intestinal mucosa by qRT-PCR. Subjects were genotyped for obesity-associated FTO variant rs9939609 by polymerase chain reaction-amplification refractory mutation system. Results: CD was associated with MeS (P = 0.01), while both CD and UC were associated with central obesity (P = 10-5, P = 0.002, respectively) and low levels of high-density lipoprotein (HDL) cholesterol (P = 5 × 10-6, P = 6 × 10-6, respectively). IBD lipid profile was characterized by decreased total and HDL cholesterol, while low-density lipoprotein cholesterol was reduced only in CD. Negative correlations were found between total cholesterol and CD activity index (P = 0.005), waist circumference and IL17A as well as IL17F mRNA levels in inflamed CD colon (P = 0.003, P = 0.001, respectively). Carriers of FTO rs9939609 AA genotype showed increased risk of CD (OR 2.6, P = 0.01). Conclusions: MeS, central obesity, and dyslipidemia could be important for IBD pathogenesis. This could influence therapeutic approaches and prevention strategies in high-risk groups. © Copyright 2020, Mary Ann Liebert, Inc., publishers 2020.

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. © 2012, SSIEM and Springer-Verlag Berlin Heidelberg.

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. © 2012, SSIEM and Springer-Verlag Berlin Heidelberg.

Hyperphenylalaninemia (HPA) [phenylketonuria (PKU) and tetrahydrobiopterin (BH4) deficiencies] is rare inborn metabolic disease characterized by elevated phenylalanine level in body fluids. In Serbia, 62 HPA patients have been identified through newborn screening since 1983. However, pterin pattern analysis is not performed. We present a patient initially diagnosed and treated as classical PKU. At 3 years of age, during infection with H1N1 influenza A virus, the patient first developed a neurologic crisis with encephalopathy and dystonic movements. We suspected that the patient is the first case of BH4 deficiency identified in Serbia. Genetic analyses showed that the patient does not have disease-causing variants of the PAH gene and carries a p.Asp136Val mutation in homozygous state in the PTS gene. For patients with treatable rare diseases, like PKU and BH4 deficiencies, correct diagnosis is crucial for the implementation of optimal treatment. If biochemical tests needed for differential diagnosis are not available, our experience emphasizes the necessity of immediate genetic testing after newborn screening. © 2015 by De Gruyter 2015.

Hyperphenylalaninemia (HPA) [phenylketonuria (PKU) and tetrahydrobiopterin (BH4) deficiencies] is rare inborn metabolic disease characterized by elevated phenylalanine level in body fluids. In Serbia, 62 HPA patients have been identified through newborn screening since 1983. However, pterin pattern analysis is not performed. We present a patient initially diagnosed and treated as classical PKU. At 3 years of age, during infection with H1N1 influenza A virus, the patient first developed a neurologic crisis with encephalopathy and dystonic movements. We suspected that the patient is the first case of BH4 deficiency identified in Serbia. Genetic analyses showed that the patient does not have disease-causing variants of the PAH gene and carries a p.Asp136Val mutation in homozygous state in the PTS gene. For patients with treatable rare diseases, like PKU and BH4 deficiencies, correct diagnosis is crucial for the implementation of optimal treatment. If biochemical tests needed for differential diagnosis are not available, our experience emphasizes the necessity of immediate genetic testing after newborn screening. © 2015 by De Gruyter 2015.