Outcomes after newborn screening for propionic and methylmalonic acidemia and homocystinurias

The current German newborn screening (NBS) panel includes 13 inherited metabolic diseases (IMDs). In addition, a NBS pilot study in Southwest Germany identifies individuals with propionic acidemia (PA), methylmalonic acidemia (MMA), combined and isolated remethylation disorders (e.g., cobalamin [cbl] C and methylenetetrahydrofolate reductase [MTHFR] deficiency), cystathionine β-synthase (CBS) deficiency, and neonatal cbl deficiency through one multiple-tier algorithm. The long-term health benefits of screened individuals are evaluated in a multicenter observational study. Twenty seven screened individuals with IMDs (PA [N = 13], MMA [N = 6], cblC deficiency [N = 5], MTHFR deficiency [N = 2] and CBS deficiency [N = 1]), and 42 with neonatal cbl deficiency were followed for a median of 3.6 years. Seventeen screened IMD patients (63%) experienced at least one metabolic decompensation, 14 of them neonatally and six even before the NBS report (PA, cbl-nonresponsive MMA). Three PA patients died despite NBS and immediate treatment. Fifteen individuals (79%) with PA or MMA and all with cblC deficiency developed permanent, mostly neurological symptoms, while individuals with MTHFR, CBS, and neonatal cbl deficiency had a favorable clinical outcome. Utilizing a combined multiple-tier algorithm, we demonstrate that NBS and specialized metabolic care result in substantial benefits for individuals with MTHFR deficiency, CBS deficiency, neonatal cbl deficiency, and to some extent, cbl-responsive MMA and cblC deficiency. However, its advantage is less evident for individuals with PA and cbl-nonresponsive MMA. SYNOPSIS: Early detection through newborn screening and subsequent specialized metabolic care improve clinical outcomes and survival in individuals with MTHFR deficiency and cystathionine-β-synthase deficiency, and to some extent in cobalamin-responsive methylmalonic acidemia (MMA) and cblC deficiency while the benefit for individuals with propionic acidemia and cobalamin-nonresponsive MMA is less evident due to the high (neonatal) decompensation rate, mortality, and long-term complications.

Influence of Season, Storage Temperature and Time of Sample Collection in Pancreatitis-Associated Protein-Based Algorithms for Newborn Screening for Cystic Fibrosis

Newborn screening (NBS) for cystic fibrosis (CF) based on pancreatitis-associated protein (PAP) has been performed for several years. While some influencing factors are known, there is currently a lack of information on the influence of seasonal temperature on PAP determination or on the course of PAP blood concentration in infants during the first year of life. Using data from two PAP studies at the Heidelberg NBS centre and storage experiments, we compared PAP determinations in summer and winter and determined the direct influence of temperature. In addition, PAP concentrations measured in CF-NBS, between days 21-35 and 36-365, were compared. Over a 7-year period, we found no significant differences between PAP concentrations determined in summer or winter. We also found no differences in PAP determination after 8 days of storage at 4 °C, room temperature or 37 °C. When stored for up to 3 months, PAP samples remained stable at 4 °C, but not at room temperature (p = 0.007). After birth, PAP in neonatal blood showed a significant increasing trend up to the 96th hour of life (p < 0.0001). During the first year of life, blood PAP concentrations continued to increase in both CF- (36-72 h vs. 36-365 d p < 0.0001) and non-CF infants (36-72 h vs. 36-365 d p < 0.0001). Seasonal effects in central Europe appear to have a limited impact on PAP determination. The impact of the increase in blood PAP during the critical period for CF-NBS and beyond on the applicability and performance of PAP-based CF-NBS algorithms needs to be re-discussed.

Collaborative evaluation study on 18 candidate diseases for newborn screening in 1.77 million samples

Analytical and therapeutic innovations led to a continuous but variable extension of newborn screening (NBS) programmes worldwide. Every extension requires a careful evaluation of feasibility, diagnostic (process) quality and possible health benefits to balance benefits and limitations. The aim of this study was to evaluate the suitability of 18 candidate diseases for inclusion in NBS programmes. Utilising tandem mass spectrometry as well as establishing specific diagnostic pathways with second-tier analyses, three German NBS centres designed and conducted an evaluation study for 18 candidate diseases, all of them inherited metabolic diseases. In total, 1 777 264 NBS samples were analysed. Overall, 441 positive NBS results were reported resulting in 68 confirmed diagnoses, 373 false-positive cases and an estimated cumulative prevalence of approximately 1 in 26 000 newborns. The positive predictive value ranged from 0.07 (carnitine transporter defect) to 0.67 (HMG-CoA lyase deficiency). Three individuals were missed and 14 individuals (21%) developed symptoms before the positive NBS results were reported. The majority of tested candidate diseases were found to be suitable for inclusion in NBS programmes, while multiple acyl-CoA dehydrogenase deficiency, isolated methylmalonic acidurias, propionic acidemia and malonyl-CoA decarboxylase deficiency showed some and carnitine transporter defect significant limitations. Evaluation studies are an important tool to assess the potential benefits and limitations of expanding NBS programmes to new diseases.

Combined Newborn Screening Allows Comprehensive Identification also of Attenuated Phenotypes for Methylmalonic Acidurias and Homocystinuria

Newborn screening (NBS) programs are effective measures of secondary prevention and have been successively extended. We aimed to evaluate NBS for methylmalonic acidurias, propionic acidemia, homocystinuria, remethylation disorders and neonatal vitamin B12 deficiency, and report on the identification of cofactor-responsive disease variants. This evaluation of the previously established combined multiple-tier NBS algorithm is part of the prospective pilot study "NGS2025" from August 2016 to September 2022. In 548,707 newborns, the combined algorithm was applied and led to positive NBS results in 458 of them. Overall, 166 newborns (prevalence 1: 3305) were confirmed (positive predictive value: 0.36); specifically, methylmalonic acidurias (N = 5), propionic acidemia (N = 4), remethylation disorders (N = 4), cystathionine beta-synthase (CBS) deficiency (N = 1) and neonatal vitamin B12 deficiency (N = 153). The majority of the identified newborns were asymptomatic at the time of the first NBS report (total: 161/166, inherited metabolic diseases: 9/14, vitamin B12 deficiency: 153/153). Three individuals were cofactor-responsive (methylmalonic acidurias: 2, CBS deficiency: 1), and could be treated by vitamin B12, vitamin B6 respectively, only. In conclusion, the combined NBS algorithm is technically feasible, allows the identification of attenuated and severe disease courses and can be considered to be evaluated for inclusion in national NBS panels.

German newborn screening for Cystic fibrosis: Parental perspectives and suggestions for improvements

PURPOSE

Cystic fibrosis (CF) was added to the German newborn bloodspot screening (NBS) panel in 2016. This study assesses parental perceptions of CF-NBS and confirmatory testing.

METHODS

Prospective questionnaire-based survey administered to parents of children with positive CF-NBS over 40 months after initiation of CF-NBS in Southwest Germany. Parental perceptions were compared to results from Bavaria and Switzerland.

RESULTS

Questionnaires with 29 standardized questions were sent to 343 families with children born between October 2016 and January 2020. A total of 178 (51.9%) replied. Although required by law, only a minority were informed about CF-NBS by a physician. The information provided about NBS was sufficient for 78% of parents. Regarding the information about positive CF-NBS, 52.9% were satisfied but the majority expressed negative emotions (89.5%). While most of these were resolved after confirmatory diagnostics, 17% of parents of children with false-positive CF-NBS and 66.7% of children confirmed with CF remained anxious. Waiting time for sweat testing was >3 days in 56.1%, considerably longer than in more centralized screening systems. Parents who waited for a maximum of 3 days were significantly more satisfied. 70.7% of parents were satisfied with the information given during confirmatory diagnostics and 91.4% were satisfied with participating in CF-NBS.

CONCLUSIONS

CF-NBS stands in high regard with parents. Smooth organization, timely initiation of confirmatory testing, and professional communication are most important to limit parental anxiety. A more centralized system of confirmatory diagnostics appears advantageous in several regards as it reduces time from positive NBS to final diagnosis and increases parental satisfaction.

Neonatal screening for isovaleric aciduria: Reducing the increasingly high false-positive rate in Germany

Newborn screening (NBS) for isovaleric acidemia (IVA) is performed by flow injection tandem mass spectrometry quantifying C5 carnitines (C5). Isovalerylcarnitine, however, is isomeric with pivaloylcarnitine which can be present in blood due to maternal use of pivaloylester-containing antibiotics, available in Germany since late 2016. During a 36-month period (January 19-December 21), all newborns screened in Hamburg with a C5 above cutoff (NeoGram®: 0.50 μmol/L or Neobase®2: 0.45 μmol/L) were included in the study. As a second-tier test, a simple ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to differentiate the C5 isomers pivaloyl-, 2-methylbutyryl-, isovaleryl-, and valerylcarnitine. Out of 156 772 newborns tested, one turned out to have genetically proven IVA while 99 were false positive (C5: 0.5-8.2 μmol/L) due to the presence of pivaloylcarnitine. These cases have increased year by year and show local clusters. Retrospective analysis of another 39 cases from 287 206 neonates tested at the NBS center in Heidelberg with C5 elevation (0.9-10.6 μmol/L) but clinical and biochemical exclusion of IVA yielded evidence of pivaloylcarnitine in all cases. Inclusion of a second-tier test into NBS significantly reduces the high and increasing false-positive rate of IVA screening. This avoids further diagnostic steps, prevents unnecessary stress and anxiety of parents in a remarkably high number of cases. If Hamburg data of 2021 are extrapolated to all of Germany, one can assume around 800 (1‰) false-positive cases in comparison to an average of two classic IVA cases per year. Unless licensing of pivaloylester-containing drugs for use during pregnancy is reconsidered, a second-tier test for C5 determination is indispensable.

Long-term anthropometric development of individuals with inherited metabolic diseases identified by newborn screening

Newborn screening (NBS) for inherited metabolic diseases (IMDs) substantially shortens a patient's journey. It enables the early start of metabolic treatment which might prevent potentially lethal neonatal disease manifestations, while promoting favorable development and long-term clinical outcomes. This study aims to assess growth in screened individuals with IMDs under different dietary regimes. Anthropometric data (3585 prospective measures) of 350 screened individuals with IMDs born between 1999 and 2018 and participating in a German prospective multicenter observational study were evaluated. Overall, birth measures were within the reference ranges, suggesting unaffected prenatal growth, except for phenylketonuria (weight) and glutaric aciduria Type 1 (head circumference). After birth, longitudinal analysis of anthropometric measures revealed a loss of height standard deviation score (SDS; -0.5 SDS; p < 0.0001), head circumference SDS (-0.2 SDS; p = 0.0028), but not for weight SDS (0.1 SDS; p = 0.5097) until the age of 18 years, while BMI SDS increased (0.4 SDS; p < 0.0001). The significant interaction with age and diet groups was pronounced for the linear growth in individuals receiving diets being low in protein, long-chain triglycerides, and galactose (p < 0.001). Identification by NBS and subsequent early (dietary) treatment cannot completely protect against alterations in growths. Disease-specific (e.g., metabolic impairments, neurotoxins) and dietary-specific (e.g., diets reduced in protein) factors may have an amplified impact on longitudinal growth. Therefore, alongside other important follow-ups, the continuous observation of the anthropometric development of screened individuals with IMDs needs special attention to early identify and support individuals at risk.

Maternal Vitamin B12 Deficiency Detected by Newborn Screening-Evaluation of Causes and Characteristics

Vitamin B12 deficiency, mostly of maternal origin in newborns, is a well-treatable condition but can cause severe neurologic sequelae in infants. Early detection of vitamin B12 deficiency allows the pre-symptomatic treatment of affected children. This evaluation assesses the characteristics of maternal vitamin B12 deficiency detected by newborn screening. In a prospective single-center study, a systematic screening strategy for vitamin B12 deficiency using a combination of two second-tier strategies was applied. In addition to confirmatory diagnostics in children, the systematic work-up of vitamin B12 status was also performed for their mothers. Maternal characteristics were assessed including ethnic origin, diet, and vitamin supplementation during pregnancy. For affected mothers, a work-up by internal medicine was recommended. In total, 121 mother-infant couples were analyzed. 66% of mothers adhered to a balanced diet including meat. The cause of maternal vitamin B12 deficiency was unknown in 56% of cases, followed by dietary causes in 32%, and organic causes in 8%. All mothers following a vegan diet and most mothers with a vegetarian diet took vitamin preparations during pregnancy, whereas only 55.8% of mothers with a balanced diet took folic acid or other vitamins. Maternal vitamin B12, folic acid, and homocysteine levels were significantly correlated with the child's folic acid levels, and with homocysteine, methylmalonic, and methylcitric acid levels in first and second NBS dried blood spots. Most children had normal blood counts and showed normocytosis. Although 36.7% of mothers showed anemia, only one presented with macrocytosis. Adherence to vitamin supplementation in pregnancy is low despite the recommendation for supplementation of folic acid. Ideally, the evaluation of mothers for vitamin B12 levels and appropriate therapy should be initiated in early pregnancy. In infants detected through newborn screening, the multidisciplinary assessment and therapy of both children and mothers should be performed.

Second-tier strategies in newborn screening – potential and limitations

Newborn screening (NBS) is a public health measure to identify children with treatable disorders within the first days of life allowing presymptomatic treatment. It is the most successful measure of secondary medical prevention and part of public health programs in many countries worldwide. Application of second-tier strategies in NBS allows for increased specificity and consecutively a higher positive predictive value. Second-tier strategies can include analysis of specific biomarkers for a target disorder or may be based on molecular genetic analyses. Improving the quality of NBS, for example by second-tier strategies, is of utmost importance to maintain the high acceptance of NBS by families – especially as an increasing number of target disorders is being consecutively included into NBS programs.

Long-term efficacy and safety of sapropterin in patients who initiated sapropterin at < 4 years of age with phenylketonuria: results of the 3-year extension of the SPARK open-label, multicentre, randomised phase IIIb trial

BACKGROUND

During the initial 26-week SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) study, addition of sapropterin dihydrochloride (Kuvan®; a synthetic formulation of the natural cofactor for phenylalanine hydroxylase, tetrahydrobiopterin; BH4), to a phenylalanine (Phe)-restricted diet, led to a significant improvement in Phe tolerance versus a Phe-restricted diet alone in patients aged 0-4 years with BH4-responsive phenylketonuria (PKU) or mild hyperphenylalaninaemia (HPA). Based on these results, the approved indication for sapropterin in Europe was expanded to include patients < 4 years of age. Herein, we present results of the SPARK extension study (NCT01376908), evaluating the long-term safety, dietary Phe tolerance, blood Phe concentrations and neurodevelopmental outcomes in patients < 4 years of age at randomisation, over an additional 36 months of treatment with sapropterin.

RESULTS

All 51 patients who completed the 26-week SPARK study period entered the extension period. Patients who were previously treated with a Phe-restricted diet only ('sapropterin extension' group; n = 26), were initiated on sapropterin at 10 mg/kg/day, which could be increased up to 20 mg/kg/day. Patients previously treated with sapropterin plus Phe-restricted diet, remained on this regimen in the extension period ('sapropterin continuous' group; n = 25). Dietary Phe tolerance increased significantly at the end of the study versus baseline (week 0), by 38.7 mg/kg/day in the 'sapropterin continuous' group (95% CI 28.9, 48.6; p < 0.0001). In the 'sapropterin extension' group, a less pronounced effect was observed, with significant differences versus baseline (week 27) only observed between months 9 and 21; dietary Phe tolerance at the end of study increased by 5.5 mg/kg/day versus baseline (95% CI - 2.8, 13.8; p = 0.1929). Patients in both groups had normal neuromotor development and growth parameters.

CONCLUSIONS

Long-term treatment with sapropterin plus a Phe-restricted diet in patients who initiated sapropterin at < 4 years of age with BH4-responsive PKU or mild HPA maintained improvements in dietary Phe tolerance over 3.5 years. These results continue to support the favourable risk/benefit profile for sapropterin in paediatric patients (< 4 years of age) with BH4-responsive PKU. Frequent monitoring of blood Phe levels and careful titration of dietary Phe intake to ensure adequate levels of protein intake is necessary to optimise the benefits of sapropterin treatment. Trial registration ClinicalTrials.gov, NCT01376908. Registered 17 June 2011, https://clinicaltrials.gov/ct2/show/NCT01376908 .

Health Outcomes of Infants with Vitamin B12 Deficiency Identified by Newborn Screening and Early Treated

OBJECTIVE

To evaluate the clinical outcomes at age 1.5 ± 0.5 years of infants with vitamin B₁₂ deficiency identified by newborn screening (NBS).

STUDY DESIGN

Prospective multicenter observational study on health outcomes of 31 infants with vitamin B₁₂ deficiency identified by NBS. Neurodevelopment was assessed by the Denver Developmental Screening Test.

RESULTS

In 285 862 newborns screened between 2016 and 2019, the estimated birth prevalence of vitamin B₁₂ deficiency was 26 in 100 000 newborns, with high seasonal variations (lowest in summer: 8 in 100 000). Infants participating in the outcome study (N = 31) were supplemented with vitamin B₁₂ for a median (range) of 5.9 (1.1-16.2) months. All achieved age-appropriate test results in Denver Developmental Screening Test at age 15 (11-23) months and did not present with symptoms characteristic for vitamin B₁₂ deficiency. Most (81%, n = 25) mothers of affected newborns had a hitherto undiagnosed (functional) vitamin B₁₂ deficiency, and, subsequently, received specific therapy.

CONCLUSIONS

Neonatal vitamin B₁₂ deficiency can be screened by NBS, preventing the manifestation of irreversible neurologic symptoms and the recurrence of vitamin B₁₂ deficiency in future pregnancies through adequate treatment of affected newborns and their mothers. The high frequency of mothers with migrant background having a newborn with vitamin B₁₂ deficiency highlights the need for improved prenatal care.

Implementing a tracking system for confirmatory diagnostic results after positive newborn screening for cystic fibrosis-implications for process quality and patient care

Newborn screening for cystic fibrosis (CF-NBS) was introduced in Germany in 2016. Currently, systematic follow-up of positive CF-NBS results is not implemented or reimbursed in the NBS program. We investigated results of confirmatory testing over 24 months after implementation of CF-NBS for a large German NBS center before and after introduction of an active tracking system and performed a cost calculation for tracking. Results are compared with the federal state of Bavaria, where a centralized tracking system has been in place for many years. At the NBS center, 244 of 281,907 children had a positive CF-NBS result requiring diagnostic confirmation. Before implementation of a telephone tracking system, only 43% of confirmatory results were returned despite repeated written requests. The consecutive strategy including telephone tracking led to an increase of resolved cases to 84%. However, the centralized tracking system in Bavaria, assigning children with positive CF-NBS directly to a responsible CF-center, resolved 99% of cases. The calculated additional cost for a tracking system in Germany including telephone tracking is 1.20€ per newborn screened.Conclusion: The implementation of a tracking system achieves a distinct improvement in CF-NBS with justifiable costs. The effect can be limited by absence of centralized organization of confirmatory testing. What is Known: • Newborn screening for cystic fibrosis (CF-NBS) has been performed for many years in several countries worldwide • While many studies have focused on different CF-NBS strategies, the organization of confirmatory testing and process quality concerning returned information to the NBS center has so far received less attention. What is New: • The implementation of an active tracking system achieves a distinct improvement of clarified cases after positive CF-NBS with justifiable costs. • The effect of a tracking system can be limited by the absence of a centralized organization of confirmatory testing.

Long-term Outcomes of Individuals With Metabolic Diseases Identified Through Newborn Screening

BACKGROUND

Although extended newborn screening (NBS) programs have been introduced more than 20 years ago, their impact on the long-term clinical outcome of individuals with inherited metabolic diseases (IMDs) is still rarely investigated.

METHODS

We studied the clinical outcomes of individuals with IMDs identified by NBS between 1999 and 2016 in a prospective multicenter observational study.

RESULTS

In total, 306 screened individuals with IMDs (115 with phenylketonuria and 191 with other IMDs with a lifelong risk for metabolic decompensation) were followed for a median time of 6.2 years. Although the risk for metabolic decompensation was disease-specific and NBS could not prevent decompensations in every individual at risk (n = 49), the majority did not develop permanent disease-specific signs (75.9%), showed normal development (95.6%) and normal cognitive outcome (87.7%; mean IQ: 100.4), and mostly attended regular kindergarten (95.2%) and primary school (95.2%). This demonstrates that not only individuals with phenylketonuria, serving as a benchmark, but also those with lifelong risk for metabolic decompensation had a favorable long-term outcome. High NBS process quality is the prerequisite of this favorable outcome. This is supported by 28 individuals presenting with first symptoms at a median age of 3.5 days before NBS results were available, by the absence of neonatal decompensations after the report of NBS results, and by the challenge of keeping relevant process parameters at a constantly high level.

CONCLUSIONS

NBS for IMDs, although not completely preventing clinical presentations in all individuals, can be considered a highly successful program of secondary prevention.

Phenylalanine Effects on Brain Function in Adult Phenylketonuria

OBJECTIVE

To evaluate the relationship between circulating phenylalanine and brain function as well as neuropsychiatric symptoms in adults with phenylketonuria.

METHODS

In this prospective cross-sectional study, early-treated patients with phenylketonuria older than 30 years and age- and sex-matched controls were included. Extensive neurologic evaluation, neuropsychological and behavioral testing, sensory and motor evoked potentials, and MRI were performed. CSF concentrations of neurodegenerative markers were evaluated in addition in a subset of 10 patients.

RESULTS

Nineteen patients with phenylketonuria (median age 41 years) with different phenylalanine levels (median 873 μmol/L) entered the study. They showed higher prevalence of neurologic symptoms, cognitive and behavioral abnormalities, autonomic dysfunction, alterations in neurophysiologic measures, and atrophy in putamen and right thalamus compared to controls. In CSF, patients with phenylketonuria exhibited higher β-amyloid 1-42 (p = 0.003), total tau (p < 0.001), and phosphorylated tau (p = 0.032) levels compared to controls. Plasma phenylalanine levels highly correlated with the number of failed neuropsychological tests (r = 0.64, p = 0.003), neuropsychiatric symptoms (r = 0.73, p < 001), motor evoked potential latency (r = 0.48, p = 0.030), and parietal lobe atrophy.

CONCLUSIONS

Our study provides strong evidence for a correlation between phenylalanine levels and clinical, neuropsychological, neurophysiologic, biochemical, and imaging alterations in adult patients with phenylketonuria.

Biotinidase deficiency: A treatable cause of hereditary spastic paraparesis

Objective

To expand the genetic spectrum of hereditary spastic paraparesis by a treatable condition and to evaluate the therapeutic effects of biotin supplementation in an adult patient with biotinidase deficiency (BD).

Methods

We performed exome sequencing (ES) in a patient with the clinical diagnosis of complex hereditary spastic paraparesis. The patient was examined neurologically, including functional rating scales. We performed ophthalmologic examinations and metabolic testing.

Results

A 41-year-old patient presented with slowly progressive lower limb spasticity combined with optic atrophy. He was clinically diagnosed with complex hereditary spastic paraparesis. The initial panel diagnostics did not reveal the disease-causing variant; therefore, ES was performed. ES revealed biallelic pathogenic variants in the BTD gene leading to the genetic diagnosis of BD. BD is an autosomal recessive metabolic disorder causing a broad spectrum of neurologic symptoms, optic atrophy, and dermatologic abnormalities. When treatment is initiated in time, symptoms can be prevented or reversed by biotin supplementation. After diagnosis in our patient, biotin supplementation was started. One year after the onset of therapy, symptoms remained stable with slight improvement of sensory deficits.

Conclusions

These findings expand the genetic spectrum of the clinical diagnosis of complex hereditary spastic paraparesis by a treatable disease. Today, most children with BD should have been identified via newborn screening to start biotin supplementation before the onset of symptoms. However, adult patients and those born in countries without newborn screening programs for BD are at risk of being missed. Therapeutic success depends on early diagnosis and presymptomatic treatment.

High throughput newborn screening for aromatic ʟ-amino-acid decarboxylase deficiency by analysis of concentrations of 3-O-methyldopa from dried blood spots

Aromatic l-amino-acid decarboxylase (AADC) deficiency is an inherited disorder of biogenic amine metabolism with a broad neurological phenotype. The clinical symptoms overlap with other diseases resulting in an often delayed diagnosis. Innovative disease-changing treatment options, particularly gene therapy, have emphasised the need for an early diagnosis. We describe the first method for 3-O-methyldopa (3-OMD) analysis in dried blood spots (DBS) suitable for high throughput newborn screening (NBS). We established a novel tandem mass spectrometry method to quantify 3-OMD in DBS and successfully tested it in 38 888 unaffected newborns, 14 heterozygous DDC variant carriers, seven known AADC deficient patients, and 1079 healthy control subjects. 3-OMD concentrations in 38 888 healthy newborns revealed a mean of 1.16 μmol/L (SD = 0.31, range 0.31-4.6 μmol/L). 1079 non-AADC control subjects (0-18 years) showed a mean 3-OMD concentration of 0.78 μmol/L (SD = 1.75, range 0.24-2.36 μmol/L) with a negative correlation with age. Inter- and intra-assay variability was low, and 3-OMD was stable over 32 days under different storage conditions. We identified seven confirmed AADC deficient patients (mean 3-OMD 9.88 μmol/L [SD = 13.42, range 1.82-36.93 μmol/L]). The highest concentration of 3-OMD was found in a NBS filter card of a confirmed AADC deficient patient with a mean 3-OMD of 35.95 μmol/L. 14 DDC variant carriers showed normal 3-OMD concentrations. We demonstrate a novel high-throughput method to measure 3-OMD in DBS, which allows integration in existing NBS programs enabling early diagnosis of AADC deficiency.

Primary carnitine deficiency - diagnosis after heart transplantation: better late than never!

Background

Primary carnitine deficiency due to mutations in the SLC22A5 gene is a rare but well-treatable metabolic disorder that puts patients at risk for metabolic decompensations, skeletal and cardiac myopathy and sudden cardiac death.

Results

We report on a 7-year-old boy diagnosed with primary carnitine deficiency 2 years after successful heart transplantation thanks his younger sister’s having been identified via expanded newborn screening during a pilot study evaluating an extension of the German newborn screening panel.

Conclusion

As L-carnitine supplementation can prevent and mostly reverse clinical symptoms of primary carnitine deficiency, all patients with cardiomyopathy should be investigated for primary carnitine deficiency even if newborn screening results were unremarkable.

Lower plasma cholesterol, LDL-cholesterol and LDL-lipoprotein subclasses in adult phenylketonuria (PKU) patients compared to healthy controls: results of NMR metabolomics investigation

Background

Phenylketonuria (PKU; OMIM#261600) is a rare metabolic disorder caused by mutations in the phenylalanine hydroxylase (PAH) gene resulting in high phenylalanine (Phe) in blood and brain. If not treated early this results in intellectual disability, behavioral and psychiatric problems, microcephaly, motor deficits, eczematous rash, autism, seizures, and developmental problems. There is a controversial discussion of whether patients with PKU have an additional risk for atherosclerosis due to interference of Phe with cholesterol synthesis and LDL-cholesterol regulation. Since cholesterol also plays a role in membrane structure and myelination, better insight into the clinical significance of the impact of Phe on lipoprotein metabolism is desirable. In 22 treated PKU patients (mean age 38.7 years) and 14 healthy controls (mean age 35.2 years), we investigated plasma with NMR spectroscopy and quantified 105 lipoprotein parameters (including lipoprotein subclasses) and 24 low molecular weight parameters. Analysis was performed on a 600 MHz Bruker AVANCE IVDr spectrometer as previously described.

Results

Concurrent plasma Phe in PKU patients showed a wide range with a mean of 899 μmol/L (50–1318 μmol/L). Total cholesterol and LDL-cholesterol were significantly lower in PKU patients versus controls: 179.4 versus 200.9 mg/dL (p < 0.02) and 79.5 versus 104.1 mg/dL (p < 0.0038), respectively. PKU patients also had lower levels of 22 LDL subclasses with the greatest differences in LDL2 Apo-B, LDL2 Particle Number, LDL2-phospholipids, and LDL2-cholesterol (p < 0.0001). There was a slight negative correlation of total cholesterol and LDL-cholesterol with concurrent Phe level. VLDL5-free cholesterol, VLDL5-cholesterol, VLDL5-phospholipids, and VLDL4-free cholesterol showed a significant (p < 0.05) negative correlation with concurrent Phe level. There was no difference in HDL and their subclasses between PKU patients and controls. Tyrosine, glutamine, and creatinine were significantly lower in PKU patients compared to controls, while citric and glutamic acids were significantly higher.

Conclusions

Using NMR spectroscopy, a unique lipoprotein profile in PKU patients can be demonstrated which mimics a non-atherogenic profile as seen in patients treated by statins.

Newborn Screening for Vitamin B12 Deficiency in Germany-Strategies, Results, and Public Health Implications

OBJECTIVE

To evaluate a systematic newborn screening (NBS) strategy for vitamin B₁₂ deficiency.

STUDY DESIGN

In a prospective single-center NBS study, a systematic screening strategy for vitamin B₁₂ deficiency was developed and evaluated. Tandem-mass spectrometry screening was complemented by 2 second-tier strategies, measuring methylmalonic/3-OH-propionic/methylcitric acid, and homocysteine from dried blood spots.

RESULTS

In a cohort of 176 702 children screened over 27 months, 33 children were detected by NBS in whom (maternal) vitamin B₁₂ deficiency was confirmed. Homocysteine was the most sensitive marker for vitamin B₁₂ deficiency, but only combination with a second-tier strategy evaluating methylmalonic acid allowed for detection of all 33 children. Mothers were of various ethnic origins, and 89% adhered to a balanced diet. Treatment in children was performed predominantly by oral vitamin B₁₂ supplementation (84%), and all children remained without clinical symptoms at short-term follow-up.

CONCLUSIONS

Vitamin B₁₂ deficiency is a treatable condition but can cause severe neurologic sequelae in infants if untreated. The proposed screening strategy is feasible and effective to identify moderate and severe cases of vitamin B₁₂ deficiency. With an incidence of 1:5355 newborns, vitamin B₁₂ deficiency is more frequent than inborn errors of metabolism included in NBS panels. Treatment of vitamin B₁₂ deficiency is easy, and additional benefits can be achieved for previously undiagnosed affected mothers. This supports inclusion of vitamin B₁₂ deficiency into NBS but also stresses the need for increased awareness of vitamin B₁₂ deficiency in caregivers of pregnant women.

Cerebrospinal fluid biogenic amines depletion and brain atrophy in adult patients with phenylketonuria

Biogenic amines synthesis in phenylketonuria (PKU) patients with high phenylalanine (Phe) concentration is thought to be impaired due to inhibition of tyrosine and tryptophan hydroxylases and competition with amino acids at the blood-brain barrier. Dopamine and serotonin deficits might explain brain damage and progressive neuropsychiatric impairment in adult PKU patients. Ten early treated adult PKU patients (mean age 38.2 years) and 15 age-matched controls entered the study. Plasma and cerebrospinal fluid (CSF) Phe, 5-hydroxyindoleacetic acid (5-HIAA), 5-hydroxytryptophan (5-HTP), 3,4-dihydroxy-l-phenylalanine (l-DOPA) and homovanillic acid (HVA) were analyzed. Voxel-based morphometry statistical nonparametric mapping was used to test the age-corrected correlation between gray matter atrophy and CSF biogenic amines levels. 5-HIAA and 5-HTP were significantly reduced in PKU patients compared to controls. Significant negative correlations were found between CSF 5-HIAA, HVA, and 5-HTP and Phe levels. A decrease in 5-HIAA and 5-HTP concentrations correlated with precuneus and frontal atrophy, respectively. Lower HVA levels correlated with occipital atrophy. Biogenic amines deficits correlate with specific brain atrophy patterns in adult PKU patients, in line with serotonin and dopamine projections. These findings may support a more rigorous Phe control in adult PKU to prevent neurotransmitter depletion and accelerated brain damage due to aging.

Newborn screening for homocystinurias: Recent recommendations versus current practice

PURPOSE

To assess how the current practice of newborn screening (NBS) for homocystinurias compares with published recommendations.

METHODS

Twenty-two of 32 NBS programmes from 18 countries screened for at least one form of homocystinuria. Centres provided pseudonymised NBS data from patients with cystathionine beta-synthase deficiency (CBSD, n = 19), methionine adenosyltransferase I/III deficiency (MATI/IIID, n = 28), combined remethylation disorder (cRMD, n = 56) and isolated remethylation disorder (iRMD), including methylenetetrahydrofolate reductase deficiency (MTHFRD) (n = 8). Markers and decision limits were converted to multiples of the median (MoM) to allow comparison between centres.

RESULTS

NBS programmes, algorithms and decision limits varied considerably. Only nine centres used the recommended second-tier marker total homocysteine (tHcy). The median decision limits of all centres were ≥ 2.35 for high and ≤ 0.44 MoM for low methionine, ≥ 1.95 for high and ≤ 0.47 MoM for low methionine/phenylalanine, ≥ 2.54 for high propionylcarnitine and ≥ 2.78 MoM for propionylcarnitine/acetylcarnitine. These decision limits alone had a 100%, 100%, 86% and 84% sensitivity for the detection of CBSD, MATI/IIID, iRMD and cRMD, respectively, but failed to detect six individuals with cRMD. To enhance sensitivity and decrease second-tier testing costs, we further adapted these decision limits using the data of 15 000 healthy newborns.

CONCLUSIONS

Due to the favorable outcome of early treated patients, NBS for homocystinurias is recommended. To improve NBS, decision limits should be revised considering the population median. Relevant markers should be combined; use of the postanalytical tools offered by the CLIR project (Collaborative Laboratory Integrated Reports, which considers, for example, birth weight and gestational age) is recommended. tHcy and methylmalonic acid should be implemented as second-tier markers.

High incidence of maternal vitamin B12 deficiency detected by newborn screening: first results from a study for the evaluation of 26 additional target disorders for the German newborn screening panel

BACKGROUND

Newborn screening (NBS) in Germany currently includes 15 target disorders. Recent diagnostic improvements suggest an extension of the screening panel.

METHODS

Since August 2016, a prospective study evaluating 26 additional target disorders (25 metabolic disorders and vitamin B₁₂-deficiency) in addition to the German screening panel is performed at the Newborn Screening Center Heidelberg. First-tier results from tandem-MS screening are complemented by second-tier strategies for 15 of the additional target disorders. NBS results of seven patients diagnosed symptomatically with one of the additional target disorders by selective screening since August 2016 are retrospectively evaluated.

RESULTS

Over a 13-month period, 68,418 children participated in the study. Second-tier analyses were performed in 5.4% of samples. Only 59 (0.1%) of study participants had abnormal screening results for one of the additional target disorders. Target disorders from the study panel were confirmed in 12 children: 1 3-hydroxy-3-methylglutaryl coenzyme A (CoA)-lyase deficiency, 1 citrullinemia type I, 1 multiple acyl-CoA dehydrogenase-deficiency, 1 methylenetetrahydrofolate reductase-deficiency, and 8 children with maternal vitamin B₁₂-deficiency. In addition, six of seven patients diagnosed symptomatically outside the study with one of the target disorders would have been identified by the study strategy in their NBS sample.

CONCLUSIONS

Within 13 months, the study "Newborn Screening 2020" identified additional 12 children with treatable conditions while only marginally increasing the recall rate by 0.1%. Maternal vitamin B₁₂-deficiency was the most frequent finding. Even more children could benefit from screening for the additional target disorders by extending the NBS panel for Germany and/or other countries.

Can untreated PKU patients escape from intellectual disability? A systematic review

Background

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.

Methods

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.

Results

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.

Conclusions

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.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0890-7) contains supplementary material, which is available to authorized users.

Incidence of maple syrup urine disease, propionic acidemia, and methylmalonic aciduria from newborn screening data

Incidence for the branched-chain intoxication-type disorders, maple syrup urine disease, propionic acidemia and methlymalonic aciduria is dependent on the population screened. Here newborn screening results from three world regions, state screening laboratories in the United States, a region in Germany and Kuwait provides new incidence numbers. Maple syrup urine disease incidence in the United States was calculated to be 1: 220219, in South-West Germany 1: 119573 (Germany nationwide 1:177978), and in Kuwait 1: 59426. Incidence of propionic acidemia alone is calculated to be 1: 242741 in the United States, 1: 284450 in South-West Germany (Germany nationwide 1:202617) and 1:59426 in Kuwait. Incidence of isolated methylmalonic aciduria alone is 1:69354 in the United States, 1:568901 in South-West Germany (Germany nationwide 1:159199) and 1: 19809 in Kuwait. In the United States several newborn screening laboratories combine their results for propionic acidemia and methylmalonic aciduria, and also include combined remethylation disorders in the respective category, resulting in an incidence of 1:50709. Combined evaluation of methylmalonic aciduria, propionic aciduria and combined remethylation disorders results in a similar incidence for Germany of 1:67539. This evaluation of newborn screening incidences reflects some population differences for three intoxication-type metabolic disorders. However, different sample sizes of the populations screened over different time periods, and differences in case definitions for methylmalonic acidurias have to be considered when interpreting these data.

Simultaneous determination of 3-hydroxypropionic acid, methylmalonic acid and methylcitric acid in dried blood spots: Second-tier LC-MS/MS assay for newborn screening of propionic acidemia, methylmalonic acidemias and combined remethylation disorders

Background and aims

Increased propionylcarnitine levels in newborn screening are indicative for a group of potentially severe disorders including propionic acidemia (PA), methylmalonic acidemias and combined remethylation disorders (MMACBL). This alteration is relatively non-specific, resulting in the necessity of confirmation and differential diagnosis in subsequent tests. Thus, we aimed to develop a multiplex approach for concurrent determination of 3-hydroxypropionic acid, methylmalonic acid and methylcitric acid from the same dried blood spot (DBS) as in primary screening (second-tier test). We also set out to validate the method using newborn and follow-up samples of patients with confirmed PA or MMACBL.

Methods

The assay was developed using liquid chromatography–tandem mass spectrometry and clinically validated with retrospective analysis of DBS samples from PA or MMACBL patients.

Results

Reliable determination of all three analytes in DBSs was achieved following simple and fast (<20 min) sample preparation without laborious derivatization or any additional pipetting steps. The method clearly distinguished the pathological and normal samples and differentiated between PA and MMACBL in all stored newborn specimens. Methylcitric acid was elevated in all PA samples; 3-hydroxypropionic acid was also high in most cases. Methylmalonic acid was increased in all MMACBL specimens; mostly together with methylcitric acid.

Conclusions

A liquid chromatography–tandem mass spectrometry assay allowing simultaneous determination of the biomarkers 3-hydroxypropionic acid, methylmalonic acid and methylcitric acid in DBSs has been developed. The assay can use the same specimen as in primary screening (second-tier test) which may reduce the need for repeated blood sampling. The presented preliminary findings suggest that this method can reliably differentiate patients with PA and MMACBL in newborn screening. The validated assay is being evaluated prospectively in a pilot project for extension of the German newborn screening panel (‟Newborn screening 2020”; Newborn Screening Center, University Hospital Heidelberg).

Newborn screening for remethylation disorders and vitamin B12 deficiency-evaluation of new strategies in cohorts from Qatar and Germany

BACKGROUND

Newborn screening is a precondition for early diagnosis and successful treatment of remethylation disorders and classical homocystinuria (cystathionine-ß-synthase deficiency). Newborn screening for classical homocystinuria using total homocysteine measurement in dried blood spots has been very successfully performed for many years for newborns from Qatar.

METHODS

A new optimized newborn screening strategy for remethylation disorders and homocystinuria was developed and evaluated for newborns from Qatar using total homocysteine measurement as first-tier and methionine, methionine-phenylalanine-ratio and propionylcarnitine as second-tiers. Proposed cut-offs were also retrospectively evaluated in newborn screening samples of 12 patients with remethylation disorders and vitamin B₁₂ deficiency from Qatar and Germany.

RESULTS

Over a 12 months period, the proposed strategy led to a decrease in the recall rate in homocysteine screening for Qatar from 1.09% to 0.68%, while allowing for additional systematic inclusion of remethylation disorders and vitamin B₁₂ deficiency into the screening panel for Qatar. In the evaluated period the applied strategy would have detected all patients with classical homocystinuria identified by the previous strategy and in addition 5 children with maternal nutritional vitamin B₁₂ deficiency and one patient with an isolated remethylation disorder. Additional retrospective evaluation of newborn screening samples of 12 patients from Germany and Qatar with remethlyation disorders or vitamin B₁₂ deficiency showed that all of these patients would have been detected by the cut-offs used in the proposed new strategy. In addition, an adapted strategy for Germany using methionine, methionine-phenylalanine-ratio and propionylcarnitine as first-tier, and homocysteine as a second-tier test was also positively evaluated retrospectively.

CONCLUSIONS

The proposed strategy for samples from Qatar allows inclusion of remethylation disorders and vitamin B₁₂ deficiency in the screening panel, while lowering the recall rate. An adapted second-tier strategy is presented for screening in Germany and will be prospectively evaluated over the next years in a pilot project named "Newborn Screening 2020".

Efficacy, safety and population pharmacokinetics of sapropterin in PKU patients <4 years: results from the SPARK open-label, multicentre, randomized phase IIIb trial

BACKGROUND

Sapropterin dihydrochloride, a synthetic formulation of BH4, the cofactor for phenylalanine hydroxylase (PAH, EC 1.14.16.1), was initially approved in Europe only for patients ≥4 years with BH4-responsive phenylketonuria. The aim of the SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) trial was to assess the efficacy (improvement in daily phenylalanine tolerance, neuromotor development and growth parameters), safety and pharmacokinetics of sapropterin dihydrochloride in children <4 years.

RESULTS

In total, 109 male or female children <4 years with confirmed BH4-responsive phenylketonuria or mild hyperphenylalaninemia and good adherence to dietary treatment were screened. 56 patients were randomly assigned (1:1) to 10 mg/kg/day oral sapropterin plus a phenylalanine-restricted diet or to only a phenylalanine-restricted diet for 26 weeks (27 to the sapropterin and diet group and 29 to the diet-only group; intention-to-treat population). Of these, 52 patients with ≥1 pharmacokinetic sample were included in the pharmacokinetic analysis, and 54 patients were included in the safety analysis. At week 26 in the sapropterin plus diet group, mean phenylalanine tolerance was 30.5 (95% confidence interval 18.7-42.3) mg/kg/day higher than in the diet-only group (p < 0.001). The safety profile of sapropterin, measured monthly, was acceptable and consistent with that seen in studies of older children. Using non-linear mixed effect modelling, a one-compartment model with flip-flop pharmacokinetic behaviour, in which the effect of weight was substantial, best described the pharmacokinetic profile. Patients in both groups had normal neuromotor development and stable growth parameters.

CONCLUSIONS

The addition of sapropterin to a phenylalanine-restricted diet was well tolerated and led to a significant improvement in phenylalanine tolerance in children <4 years with BH4-responsive phenylketonuria or mild hyperphenylalaninemia. The pharmacokinetic model favours once per day dosing with adjustment for weight. Based on the SPARK trial results, sapropterin has received EU approval to treat patients <4 years with BH4-responsive phenylketonuria.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01376908 . Registered June 17, 2011.

Genetic cause and prevalence of hydroxyprolinemia

BACKGROUND

Hydroxyprolinemia is an inborn error of amino acid degradation that is considered a non-disease. Known for more than 50 years, its genetic cause and prevalence have remained unclear. In MS/MS newborn screening, the mass spectrum of hydroxyproline cannot be differentiated from isoleucine and leucine causing false positive newborn screening test results for maple syrup urine disease (MSUD).

METHODS

We studied two siblings with hydroxyprolinemia via exome sequencing and confirmed the candidate gene in five further individuals with hydroxyprolinemia, who were all characterized biochemically and clinically. The prevalence was calculated based on the number of individuals with hydroxyprolinemia detected via MS/MS newborn screening at our centre from 2003 to 2014.

RESULTS

In six cases, we identified homozygous or compound heterozygous mutations in PRODH2 as the underlying genetic cause of hydroxyprolinemia. One individual was heterozygous for a deletion in PRODH2 and had an intermittent biochemical phenotype with partial normalization of hydroxyproline concentrations. In one further individual with persistent hydroxyprolinemia no mutation in PRODH2 was found, raising the possibility of another defect of hydroxyproline degradation yet to be identified as the underlying cause of hydroxyprolinemia. Plasma hydroxyproline concentrations were clearly elevated in all individuals with biallelic mutations in PRODH2. All studied individuals remained asymptomatic, giving further evidence that hydroxyprolinemia is a benign condition. The estimated prevalence of hydroxyprolinemia in Germany is about one in 47,300 newborns.

CONCLUSION

Our results establish mutations in PRODH2 as a cause of human hydroxyprolinemia via impaired dehydrogenation of hydroxyproline to delta1-pyroline-3-hydroxy-5-carboxylic acid, and we suggest PRODH2 be renamed HYPDH. Hydroxyprolinemia is an autosomal-recessively inherited benign condition. It is a frequent cause of false positive screening results for MSUD, the prevalence being about 2.5 times higher than that of MSUD.

Long-chain polyunsaturated fatty acid status in children, adolescents and adults with phenylketonuria

BACKGROUND

Patients with phenylketonuria have been reported to be deficient in long-chain polyunsaturated fatty acids (LCPUFAs). It has been postulated that good compliance with the dietary regimen negatively influences LCPUFA status.

METHODS

In 36 patients with phenylketonuria and 18 age-matched healthy control subjects LCPUFA-levels in plasma phospholipids and cholesteryl esters, erythrocyte phosphatidylcholine and phosphatidylethanolamine were evaluated.

RESULTS

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels did not differ significantly between patients and control subjects in plasma and erythrocyte fractions. There was a significant negative correlation between SDS (standard deviation) scores of DHA-levels in erythrocyte parameters from the respective age-matched control group and patients' concurrent and long-term phenylalanine levels for erythrocyte phosphatidylethanolamine and erythrocyte phosphatidylcholine. Patients with lower (higher) phenylalanine levels had positive (negative) DHA-SDS.

CONCLUSION

In contrast to previous reports we did not find lower LCPUFA-levels in patients with phenylketonuria compared to age-matched healthy control subjects. Good dietary control was associated with better LCPUFA status.

Medium-Chain Acyl-CoA Dehydrogenase Deficiency: Evaluation of Genotype-Phenotype Correlation in Patients Detected by Newborn Screening

BACKGROUND

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is included in many newborn screening programmes worldwide. In addition to the prevalent mutation c.985A>G in the ACADM gene, potentially mild mutations like c.199T>C are frequently found in screening cohorts. There is ongoing discussion whether this mutation is associated with a clinical phenotype.

METHODS

In 37 MCADD patients detected by newborn screening, biochemical phenotype (octanoylcarnitine (C8), ratios of C8 to acetylcarnitine (C2), decanoylcarnitine (C10) and dodecanoylcarnitine (C12) at screening and confirmation) and clinical phenotype (inpatient emergency treatment, metabolic decompensations, clinical assessments, psychometric tests) were assessed in relation to genotype.

RESULTS

16 patients were homozygous for c.985A>G (group 1), 11 compound heterozygous for c.199T>C and c.985A>G/another mutation (group 2) and 7 compound heterozygous for c.985A>G and mutations other than c.199T>C (group 3) and 3 carried neither c.985A>G nor c.199T>C but other known homozygous mutations (group 4). At screening C8/C2 and C8/C10, at confirmation C8/C2, C8/C10 and C8/C12 differed significantly between patients compound heterozygous for c.199T>C (group 2) and other genotypes. C8, C10 and C8/C2 at screening were strongly associated with time of sampling in groups 1 + 3 + 4, but not in group 2. Clinical phenotype did not differ between genotypes. Two patients compound heterozygous for c.199T>C and a severe mutation showed neonatal decompensation with hypoglycaemia.

CONCLUSION

Biochemical phenotype differs between MCADD patients compound heterozygous for c.199T>C with a severe mutation and other genotypes. In patients detected by newborn screening, clinical phenotype does not differ between genotypes following uniform treatment recommendations. Neonatal decompensation can also occur in patients with the presumably mild mutation c.199T>C prior to diagnosis.

Living with an inborn error of metabolism detected by newborn screening-parents' perspectives on child development and impact on family life

BACKGROUND

Newborn screening for inborn errors of metabolism is regarded as highly successful by health professionals. Little is known about parents' perspectives on child development and social impact on families.

METHODS

Parents of 187 patients with metabolic disorders detected by newborn screening rated child development, perceived burdens on child and family, and future expectations on a questionnaire with standardized answers. Parental ratings were compared with standardized psychometric test results. Regression analysis was performed to identify factors associated with extent of perceived burden.

RESULTS

In 26.2% of patients, parents perceived delays in global development and/or specific developmental domains (physical, social, intellectual, language). Parents expected normal future development in 95.7%, and an independent adult life for their child in 94.6%. Comparison with psychometric test results showed that parents of children with cognitive impairments tended to overrate their child's abilities. Mild/medium burden posed on the family (child) by the metabolic disorder was stated by 56.1% (48.9%) of parents, severe/very severe burden by 19.3% (8.6%). One third of families reported financial burden due to the metabolic disorder. Dietary treatment and diagnoses with risk for metabolic decompensation despite treatment were associated with higher perceived burden for the family. Disorders rated as potentially very burdensome by experts were not rated accordingly by parents, demonstrating different perspectives of professionals and parents.

CONCLUSION

Although newborn screening leads to favourable physical and cognitive outcome, living with a metabolic disorder may cause considerable stress on patients and families, emphasizing the need for comprehensive multidisciplinary care including psychological and social support.

Results of a patient-directed survey on frequency of family history of glaucoma in 2170 patients

PURPOSE

To evaluate in different types of glaucoma frequency of family history of glaucoma (FHG), age at diagnosis, glaucoma risk in relatives, and acceptance rate of genetic glaucoma tests. To assess stage of visual field loss (VFL) in relation to FHG.

METHODS

Using standardized questions whether an ophthalmologist had found or excluded glaucoma or ocular hypertension (OH), 2170 patients with glaucoma or OH interviewed all their first and second degree relatives. One thousand three hundred thirty-eight patients had POAG, 233 primary angle closure glaucoma (PACG), 148 OH, 153 normal tension glaucoma (NTG), 50 pigmentary glaucoma (PG), and 66 pseudoexfoliation glaucoma (PEX).

RESULTS

Frequency of FHG was 40% in POAG, without significant differences compared with NTG (P = 0.08), OH (P = 0.5), PACG (P = 0.4), and PG (P = 0.6). There were significant differences in age at diagnosis between the glaucomas (smallest between group P < 0.0001). Patients with FHG were significantly younger at diagnosis than patients without FHG in all types of glaucoma (all P values ≤ 0.03), except NTG and PEX. Patients' siblings and mothers had the highest detection probability for glaucoma in POAG and OH. There was no significant relation between stage of VFL and FHG in POAG (P = 0.6). Sixty-eight percent of patients would participate in genetic glaucoma tests.

CONCLUSIONS

There is a similarly high genetic disposition in all types of glaucoma. Disease risk was especially high in mothers and siblings. In patients with FHG, knowledge of genetic disposition of the glaucomas may have led to earlier diagnosis. This highlights the need for glaucoma awareness campaigns.

Visual functions in phenylketonuria-evaluating the dopamine and long-chain polyunsaturated fatty acids depletion hypotheses

BACKGROUND

In phenylketonuria presymptomatic treatment following newborn screening prevents severe mental and physical impairment. The reasons for subtle impairments of cerebral functions despite early treatment remain unclear. We assessed a broad spectrum of visual functions in early-treated patients with phenylketonuria and evaluated two hypotheses-the dopamine and the long-chain polyunsaturated fatty acids (LCPUFAs) depletion hypotheses.

METHODS

Contrast sensitivity, colour vision, electroretinography, frequency doubling technology campimetry (FDT), and their relation with blood phenylalanine and docosahexaenoic acid levels were assessed in 36 patients with phenylketonuria and 18 age-matched healthy controls.

RESULTS

Contrast sensitivity was significantly lower and total error scores in colour vision significantly higher in patients than controls. Electroretinography results differed significantly between patients and controls. We found a trend for the effect of phenylalanine-levels on contrast sensitivity and a significant effect on colour vision/FDT results. Docosahexaenoic acid levels in erythrocytes were not associated with visual functions.

CONCLUSION

This is the first evaluation of visual functions in phenylketonuria using a comprehensive ophthalmological test battery. We found no evidence supporting the long-chain polyunsaturated fatty acids depletion hypothesis. However, the effect of phenylalanine-levels on visual functions suggests that imbalance between phenylalanine and tyrosine may affect retinal dopamine levels in phenylketonuria. This is supported by the similar patterns of visual functions in patients with phenylketonuria observed in our study and patients with Parkinson's disease.

Glucose transporter-1 (GLUT1) deficiency syndrome: diagnosis and treatment in late childhood

BACKGROUND

Typical cases of glucose transporter-1 deficiency syndrome (GLUT1-DS) present with early-onset epilepsy. We report symptoms, diagnostic results, and effects of therapy in two patients diagnosed with GLUT1-DS at the age of 10 and 15 years, respectively.

PATIENTS

Patient 1: After four cerebral seizures in the first 2 years of life the patient was seizure-free but showed a complex movement disorder, expressive speech disorder, and mental retardation. Ratio of cerebrospinal fluid (CSF) to blood glucose was 0.41 (reference range 0.65 ± 0.1), molecular genetic testing confirmed GLUT1 deficiency with the novel pathogenic mutation c.1377dupC (p.Phe460LeufsX3) in the SLC2A1 gene. Following 9 months of ketogenic diet started at the age of 10 years, there was distinct improvement of speech and movement disorder. Patient 2 showed pharmacorefractive epilepsy, mental retardation, and a mild movement disorder. At the age of 15 years, extensive intake of food with high fat content was observed. Ratio of CSF to blood glucose was 0.41 (reference range 0.65 ± 0.1). The pathogenic mutation c.634C>T (p.Arg212Cys) was found in the SLC2A1 gene.

CONCLUSION

Self-induced high-fat diet can be a hint toward GLUT1-DS. Ketogenic diet can be beneficial even when started in late childhood, although it may take several months to achieve a positive effect.

[Pseudoexfoliation syndrome: no central zone of pseudoexfoliation material in patients with pseudophakia - a clinical study]

BACKGROUND, MATERIAL AND METHODS

1. An evaluation of medical findings and photodocumentation of 6 patients with pseudoexfoliation (PEX) material on the anterior surface of posterior chamber intraocular lenses was undertaken. Molecular genetic analysis of mutations in LOX-L1 was performed in order to confirm the association with pseudoexfoliation syndrome or glaucoma. Age of patients, the maximal intraocular pressure and perimetry with Octopus and Goldmann perimeters were documented as well as the time between implantation of the posterior chamber lens and diagnosis of pseudoexfoliation material on the anterior surface of posterior chamber lens. 2. Consecutive examinations of 35 patients with pseudoexfoliation syndrome or -glaucoma and pseudophakia were made to evaluate the frequency of patients with pseudoexfoliation material on the anterior surface of posterior chamber lenses.

RESULTS

1. The characteristic formation of stripe-shaped peripheral pseudoexfoliation material is seen in all examined patients on the anterior surface of posterior chamber lenses, but there is no central homogeneous round zone of pseudoexfoliation material in all patients. 2. the mean observation time of patients with pseudophakia and pseudoexfoliation syndrome or glaucoma is 4.4 ± 3.9 years. 5.7 % of the patients show pseudoexfoliation material in the periphery of posterior chamber lenses. The mean time between implantation of the intraocular lens and diagnosis of pseudoexfoliation material on the lenses is 3 years.

CONCLUSIONS

The lack of a central homogeneous round zone of pseudoexfoliation material deposits on the anterior surface of posterior chamber lenses seems to be characteristic. The change in topography of PEX material on intraocular lenses is described here for the first time. A knowledge of this change in the topography of pseudoexfoliation material in pseudophakia is important for glaucoma screening, because pseudoexfoliation deposits can only be detected in mydriasis due to the peripheral location on the intraocular lens. Due to the old age of patients at the onset of pseudoexfoliation deposits, a pseudoexfoliation syndrome frequently is likely to develop after cataract surgery in many patients.

Efficacy and outcome of expanded newborn screening for metabolic diseases--report of 10 years from South-West Germany

BACKGROUND

National newborn screening programmes based on tandem-mass spectrometry (MS/MS) and other newborn screening (NBS) technologies show a substantial variation in number and types of disorders included in the screening panel. Once established, these methods offer the opportunity to extend newborn screening panels without significant investment and cost. However, systematic evaluations of newborn screening programmes are rare, most often only describing parts of the whole process from taking blood samples to long-term evaluation of outcome.

METHODS

In a prospective single screening centre observational study 373 cases with confirmed diagnosis of a metabolic disorder from a total cohort of 1,084,195 neonates screened in one newborn screening laboratory between January 1, 1999, and June 30, 2009 and subsequently treated and monitored in five specialised centres for inborn errors of metabolism were examined. Process times for taking screening samples, obtaining results, initiating diagnostic confirmation and starting treatment as well as the outcome variables metabolic decompensations, clinical status, and intellectual development at a mean age of 3.3 years were evaluated.

RESULTS

Optimal outcome is achieved especially for the large subgroup of patients with medium-chain acyl-CoA dehydrogenase deficiency. Kaplan-Meier-analysis revealed disorder related patterns of decompensation. Urea cycle disorders, organic acid disorders, and amino acid disorders show an early high and continuous risk, medium-chain acyl-CoA dehydrogenase deficiency a continuous but much lower risk for decompensation, other fatty acid oxidation disorders an intermediate risk increasing towards the end of the first year. Clinical symptoms seem inevitable in a small subgroup of patients with very early disease onset. Later decompensation can not be completely prevented despite pre-symptomatic start of treatment. Metabolic decompensation does not necessarily result in impairment of intellectual development, but there is a definite association between the two.

CONCLUSIONS

Physical and cognitive outcome in patients with presymptomatic diagnosis of metabolic disorders included in the current German screening panel is equally good as in phenylketonuria, used as a gold standard for NBS. Extended NBS entails many different interrelated variables which need to be carefully evaluated and optimized. More reports from different parts of the world are needed to allow a comprehensive assessment of the likely benefits, harms and costs in different populations.

Blood phenylalanine concentrations in patients with PAH-deficient hyperphenylalaninaemia off diet without and with three different single oral doses of tetrahydrobiopterin: assessing responsiveness in a model of statistical process control

Tetrahydrobiopterin (BH(4)) cofactor loading is a standard procedure to differentiate defects of BH(4) metabolism from phenylalanine hydroxylase (PAH) deficiency. BH(4) responsiveness also exists in PAH-deficient patients with high residual PAH activity. Unexpectedly, single cases with presumed nil residual PAH activity have been reported to be BH(4) responsive, too. BH(4) responsiveness has been defined either by a >or=30% reduction of blood Phe concentration after a single BH(4) dose or by a decline greater than the individual circadian Phe level variation. Since both methods have methodological disadvantages, we present a model of statistical process control (SPC) to assess BH(4) responsiveness. Phe levels in 17 adult PKU patients of three phenotypic groups off diet were compared without and with three different single oral dosages of BH(4) applied in a double-blind randomized cross-over design. Results are compared for >or=30% reduction and SPC. The effect of BH(4) by >or=30% reduction was significant for groups (p < 0.01) but not for dose (p = 0.064), with no interaction of group with dose (p = 0.24). SPC revealed significant effects for group (p < 0.01) and the interaction for group with dose (p < 0.05) but not for dose alone (p = 0.87). After one or more loadings, seven patients would be judged to be BH(4) responsive either by the 30% criterion or by the SPC model, but only three by both. Results for patients with identical PAH genotype were not very consistent within (for different BH(4) doses) and between the two models. We conclude that a comparison of protein loadings without and with BH(4) combined with a standardized procedure for data analysis and decision would increase the reliability of diagnostic results.

Pharmacokinetics of tetrahydrobiopterin following oral loadings with three single dosages in patients with phenylketonuria

BACKGROUND

Tetrahydrobiopterin (BH(4)) loading has been performed for many years in patients detected by newborn screening for hyperphenylalaninaemia (HPA) to distinguish BH(4) cofactor synthesis or recycling defects from phenylalanine hydroxylase (PAH)-deficient HPA. Previous studies have shown that the pharmacokinetics of BH(4) shows high intra-individual and inter-individual variability.

METHODS

Seventeen adult patients with PAH-deficient HPA were classified in one of three phenotypic groups (mild, moderate, classical PKU) according to their response to a standardized protein loading test. Genotype information was available for all participants. In a randomized controlled double-blind design, BH(4) loadings in single oral dosages of 10, 20 and 30 mg BH(4)/kg body weight (bw) were performed to assess BH(4) responsiveness. As part of this study, levels of BH(4) metabolites in dried blood spots were studied to provide information on the pharmacokinetics of BH(4) following oral administration.

RESULTS

Levels of biopterin and pterin (B + P) increased significantly with increasing BH(4) dose (p < 0.0001). Maximum B + P levels were reached 4 hours after application of BH(4). There was no significant difference in BH(4) pharmacokinetics between the three phenotypic groups of PKU. Male and female patients showed different levels of BH(4) metabolites following 10 mg BH(4)/kg bw, but not following 20 and 30 mg BH(4)/kg bw. There was no relationship between age of patients and BH(4) pharmacokinetics. There was no correlation between B + P levels and decrease in Phe level (p = 0.69).

CONCLUSION

BH(4) pharmacokinetics are variable between patients regarding absolute levels of BH(4) metabolites reached after BH(4) loading, but are similar regarding the interval to individual maximum B + P levels. Levels of B + P increase significantly with increasing BH(4) doses. There is no correlation between B + P levels and decrease in Phe level.

Effects and clinical significance of tetrahydrobiopterin supplementation in phenylalanine hydroxylase-deficient hyperphenylalaninaemia

In recent years several studies on tetrahydrobiopterin (BH4)-responsive phenylalanine hydroxylase (PAH) deficiency have been published. The molecular mechanisms of BH4 responsiveness are not conclusively understood, but there is evidence that BH4 responsiveness in hyperphenylalaninaemia (HPA) depends on the patient's genotype and residual PAH activity. As a BH4 preparation will soon obtain marketing approval as an alternative treatment for phenylketonuria (PKU), it is particularly important to evaluate this treatment and to define criteria to identify patients with a potential benefit from it. Most of the patients found to be BH4-responsive suffered from mild PKU or mild hyperphenylalaninaemia (MHP) and some of these would not be treated at all in many countries. Of patients with moderate and classic forms of PKU, only a few were classified as responders and the clinical significance of the effect size may be small.