Efficacy and safety of sapropterin before and during pregnancy: Final analysis of the Kuvan® Adult Maternal Paediatric European Registry (KAMPER) maternal and Phenylketonuria Developmental Outcomes and Safety (PKUDOS) PKU-MOMs sub-registries

Infants born to mothers with phenylketonuria (PKU) may develop congenital abnormalities because of elevated phenylalanine (Phe) levels in the mother during pregnancy. Maintenance of blood Phe levels between 120 and 360 μmol/L reduces risks of birth defects. Sapropterin dihydrochloride helps maintain blood Phe control, but there is limited evidence on its risk-benefit ratio when used during pregnancy. Data from the maternal sub-registries-KAMPER (NCT01016392) and PKUDOS (NCT00778206; PKU-MOMs sub-registry)-were collected to assess the long-term safety and efficacy of sapropterin in pregnant women in a real-life setting. Pregnancy and infant outcomes, and the safety of sapropterin were assessed. Final data from 79 pregnancies in 57 women with PKU are reported. Sapropterin dose was fairly constant before and during pregnancy, with blood Phe levels maintained in the recommended target range during the majority (82%) of pregnancies. Most pregnancies were carried to term, and the majority of liveborn infants were reported as 'normal' at birth. Few adverse and serious adverse events were considered related to sapropterin, with these occurring in participants with high blood Phe levels. This report represents the largest population of pregnant women with PKU exposed to sapropterin. Results demonstrate that exposure to sapropterin during pregnancy was well-tolerated and facilitated maintenance of blood Phe levels within the target range, resulting in normal delivery. This critical real-world data may facilitate physicians and patients to make informed treatment decisions about using sapropterin in pregnant women with PKU and in women of childbearing age with PKU who are responsive to sapropterin.

A multinational study of acute and long-term outcomes of Type 1 galactosemia patients who carry the S135L (c.404C > T) variant of GALT

Patients with galactosemia who carry the S135L (c.404C > T) variant of galactose-1-P uridylyltransferase (GALT), documented to encode low-level residual GALT activity, have been under-represented in most prior studies of outcomes in Type 1 galactosemia. What is known about the acute and long-term outcomes of these patients, therefore, is based on very limited data. Here, we present a study comparing acute and long-term outcomes of 12 patients homozygous for S135L, 25 patients compound heterozygous for S135L, and 105 patients homozygous for two GALT-null (G) alleles. This is the largest cohort of S135L patients characterized to date. Acute disease following milk exposure in the newborn period was common among patients in all 3 comparison groups in our study, as were long-term complications in the domains of speech, cognition, and motor outcomes. In contrast, while at least 80% of both GALT-null and S135L compound heterozygous girls and women showed evidence of an adverse ovarian outcome, prevalence was only 25% among S135L homozygotes. Further, all young women in this study with even one copy of S135L achieved spontaneous menarche; this is true for only about 33% of women with classic galactosemia. Overall, we observed that while most long-term outcomes trended milder among groups of patients with even one copy of S135L, many individual patients, either homozygous or compound heterozygous for S135L, nonetheless experienced long-term outcomes that were not mild. This was true despite detection by newborn screening and both early and life-long dietary restriction of galactose. This information should empower more evidence-based counseling for galactosemia patients with S135L.

Addition of MPS-II to the Recommended Uniform Screening Panel in the United States

It has recently been announced that the Secretary of the U.S. Department of Health and Human Services has approved the recommendation by the Advisory Committee on Heritable Disorders in Newborns and Children (ACHDNC) to add mucopolysaccharidosis type II (MPS-II, Hunter Syndrome) to the recommended uniform screening panel (RUSP) in the United States [...].

Population-Based Screening of Newborns: Findings From the NBS Expansion Study (Part One)

Each year, through population-based newborn screening (NBS), 1 in 294 newborns is identified with a condition leading to early treatment and, in some cases, life-saving interventions. Rapid advancements in genomic technologies to screen, diagnose, and treat newborns promise to significantly expand the number of diseases and individuals impacted by NBS. However, expansion of NBS occurs slowly in the United States (US) and almost always occurs condition by condition and state by state with the goal of screening for all conditions on a federally recommended uniform panel. The Newborn Screening Translational Research Network (NBSTRN) conducted the NBS Expansion Study to describe current practices, identify expansion challenges, outline areas for improvement in NBS, and suggest how models could be used to evaluate changes and improvements. The NBS Expansion Study included a workshop of experts, a survey of clinicians, an analysis of data from online repositories of state NBS programs, reports and publications of completed pilots, federal committee reports, and proceedings, and the development of models to address the study findings. This manuscript (Part One) reports on the design, execution, and results of the NBS Expansion Study. The Study found that the capacity to expand NBS is variable across the US and that nationwide adoption of a new condition averages 9.5 years. Four factors that delay and/or complicate NBS expansion were identified. A companion paper (Part Two) presents a use case for each of the four factors and highlights how modeling could address these challenges to NBS expansion.

Clinical Effectiveness of Telemedicine-Based Pediatric Genetics Care

BACKGROUND AND OBJECTIVES

Telemedicine may increase access to medical genetics care. However, in the pediatric setting, how telemedicine may affect the diagnostic rate is unknown, partially because of the perceived importance of the dysmorphology physical examination. We studied the clinical effectiveness of telemedicine for patients with suspected or confirmed genetic conditions.

METHODS

We conducted a retrospective cohort study of outpatient encounters before and after the widespread implementation of telemedicine (N = 5854). Visit types, diagnoses, patient demographic characteristics, and laboratory data were acquired from the electronic health record. Patient satisfaction was assessed through survey responses. New molecular diagnosis was the primary end point.

RESULTS

Patients seen by telemedicine were more likely to report non-Hispanic White ancestry, prefer to speak English, live in zip codes with higher median incomes, and have commercial insurance (all P < .01). Genetic testing was recommended for more patients evaluated by telemedicine than in person (79.5% vs 70.9%; P < .001). Patients seen in person were more likely to have a sample collected, resulting in similar test completion rates (telemedicine, 51.2%; in person, 55.1%; P = .09). There was no significant difference in molecular diagnosis rate between visit modalities (telemedicine, 13.8%; in person, 12.4%; P = .40).

CONCLUSIONS

Telemedicine and traditional in-person evaluation resulted in similar molecular diagnosis rates. However, improved methodologies for remote sample collection may be required. This study reveals the feasibility of telemedicine in a large academic medical genetics practice and is applicable to other pediatric specialties with perceived importance of physical examination.

O-307 Cannabidiol as a potential novel treatment for endometriosis by its anti-inflammatory and anti-oxidative effects in an experimental rat model

Study question

Can cannabidiol (CBD) - a nonpsychoactive constituent of the cannabis plant – be used in the treatment of endometriosis by its anti-inflammatory and anti-oxidative effects?

Summary answer

CBD appears to be a potential novel therapeutic agent in the treatment of endometriosis through inhibiting inflammation and decreasing oxidative stress in a dose-dependent manner.

What is known already

The endocannabinoid system (ECS) consists of various bioactive lipids that are produced endogenously which activate cannabinoid 1-2 receptors (CB1-2). Alterations in ECS are associated with many physiological and pathological conditions throughout the body including endometriosis. The events that play role in the development and growth of ectopic endometriotic implants are proliferation, angiogenesis, and inflammation. By their anti-inflammatory and anti-oxidative effects, phyto and synthetic cannabinoids had been investigated and started being used for diseases with similar mechanisms. CBD is a nonpsychoactive constituent of the cannabis plant which acts indirectly upon the CB-1 receptor and as an inverse agonist of CB-2 receptor.

Study design, size, duration

Endometrial implants were surgically induced in 36 female Wistar-Albino rats in the first surgery. After confirmation of endometriotic foci in the second surgery, the rats were randomized into four groups. Group 1 (leuprolide acetate group) was given a single 1 mg/kg subcutaneous injection of leuprolide acetate. Groups 2,3 and 4 were 5 mg/kg CBD, saline solution (control group), and 20 mg/kg CBD injected groups, respectively, and daily intra-peritoneal (i.p.) injections were applied for seven days.

Participants/materials, setting, methods

After 21 days from the second surgery, the rats were sacrificed and histopathological analysis of endometriotic lesions, total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), interleukin 1 (IL-1), interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-a) measurements in blood and peritoneal fluid samples, and immunohistochemical staining for TNF-a expression in endometriotic tissue were evaluated.

Main results and the role of chance

After treatment, significant reductions in TOS, OSI, IL-1, IL-6 and TNF-α levels in the blood and peritoneal fluid samples and TNF-α expression of endometriotic implants (p &lt; 0.01) and increased TAS (p &lt; 0.01) were found in the CBD 5mg/kg and leuprolide acetate groups.

Limitations, reasons for caution

The limitation is that this is an experimental rat model study.

Wider implications of the findings

This is the first study in the literature that evaluates the effects of a phytocannabinoid -CBD- on endometriosis in a rat model. With its anti-inflammatory and anti-oxidative effects and favorable safety and tolerability profile, it might be a candidate for a novel treatment in endometriosis.

Trial registration number

not applicable

The diagnosis and management of Gaucher disease in pediatric patients: Where do we go from here?

Gaucher disease (GD) is an autosomal recessive inherited lysosomal storage disease that often presents in early childhood and is associated with damage to multiple organ systems. Many challenges associated with GD diagnosis and management arise from the considerable heterogeneity of disease presentations and natural history. Phenotypic classification has traditionally been based on the absence (in type 1 GD) or presence (in types 2 and 3 GD) of neurological involvement of varying severity. However, patient management and prediction of prognosis may be best served by a dynamic, evolving definition of individual phenotype rather than by a rigid system of classification. Patients may experience considerable delays in diagnosis, which can potentially be reduced by effective screening programs; however, program implementation can involve ethical and practical challenges. Variation in the clinical course of GD and an uncertain prognosis also complicate decisions concerning treatment initiation, with differing stakeholder perspectives around efficacy and acceptable cost/benefit ratio. We review the challenges faced by physicians in the diagnosis and management of GD in pediatric patients. We also consider future directions and goals, including acceleration of accurate diagnosis, improvements in the understanding of disease heterogeneity (natural history, response to treatment, and prognosis), the need for new treatments to address unmet needs for all forms of GD, and refinement of the tools for monitoring disease progression and treatment efficacy, such as specific biomarkers.

Epimutations in both the TESK2 and MMACHC promoters in the Epi-cblC inherited disorder of intracellular metabolism of vitamin B12

Background

epi-cblC is a recently discovered inherited disorder of intracellular vitamin B₁₂ metabolism associating hematological, neurological, and cardiometabolic outcomes. It is produced by an epimutation at the promoter common to CCDC163P and MMACHC, which results from an aberrant antisense transcription due to splicing mutations in the antisense PRDX1 gene neighboring MMACHC. We studied whether the aberrant transcription produced a second epimutation by encompassing the CpG island of the TESK2 gene neighboring CCDC163P.

Methods

We unraveled the methylome architecture of the CCDC163P–MMACHC CpG island (CpG:33) and the TESK2 CpG island (CpG:51) of 17 epi-cblC cases. We performed an integrative analysis of the DNA methylome profiling, transcriptome reconstruction of RNA-sequencing (RNA-seq), chromatin immunoprecipitation sequencing (ChIP-Seq) of histone H3, and transcription expression of MMACHC and TESK2.

Results

The PRDX1 splice mutations and activation of numerous cryptic splice sites produced antisense readthrough transcripts encompassing the bidirectional MMACHC/CCDC163P promoter and the TESK2 promoter, resulting in the silencing of both the MMACHC and TESK2 genes through the deposition of SETD2-dependent H3K36me3 marks and the generation of epimutations in the CpG islands of the two promoters.

Conclusions

The antisense readthrough transcription of the mutated PRDX1 produces an epigenetic silencing of MMACHC and TESK2. We propose using the term 'epi-digenism' to define this epigenetic disorder that affects two genes. Epi-cblC is an entity that differs from cblC. Indeed, the PRDX1 and TESK2 altered expressions are observed in epi-cblC but not in cblC, suggesting further evaluating the potential consequences on cancer risk and spermatogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01271-1.

Perceptions and use of phenylbutyrate metabolite testing in urea cycle disorders: Results of a clinician survey and analysis of a centralized testing database

The nitrogen scavengers sodium and glycerol phenylbutyrate (PB), approved for chronic treatment of urea cycle disorders (UCDs), undergo hepatic conversion to phenylacetate (PAA), which conjugates glutamine to form phenylacetylglutamine for urinary nitrogen excretion. Elevated PAA has been associated with reversible neurological toxicity, with symptoms similar to hyperammonemia. Plasma PB metabolite analysis can assess for toxicity and therapeutic drug levels. An online survey was undertaken to assess US clinician perceptions and use of the test in addition to an analysis of centralized US laboratory records. Survey responses from 52 clinicians were analyzed, including 58% who reported using plasma PB metabolite testing. Test users reported managing more UCD patients than nonusers. Users rated the test as "often helpful" for ruling out PAA toxicity (44%), informing PB dosing decisions (42%), and assessing adherence (28%). Test results were reported as most often unremarkable (61%) or suggestive of poor adherence (13%); 46% of users had never encountered results indicative of PAA toxicity. Analyses of laboratory records for 1668 plasma metabolite tests determined that only 5% of samples had plasma PAA-to-phenylacetylglutamine ratios associated with increased risk of PAA toxicity. Nearly half of surveyed clinicians were unsure of metabolite targets; those conducting ad hoc (versus regular) testing were significantly more likely to be unsure of targets. One-fifth of test users identified uncertainties, including questions about test validation, timing, and interpretation. Increased awareness of published PB metabolite data and further clinician education on test interpretation may help to inform the use of metabolite testing to optimize UCD care.

The Editor's Choice for Issue 2, Volume 7

Dear readers: I am proud to say that we are continuing to publish many important papers on newborn screening in IJNS, and the papers published in this issue clearly support my statement [...].

Should patients with Phosphomannomutase 2-CDG (PMM2-CDG) be screened for adrenal insufficiency?

PMM2-CDG is the most common congenital disorder of glycosylation (CDG) accounting for almost 65% of known CDG cases affecting N-glycosylation. Abnormalities in N-glycosylation could have a negative impact on many endocrine axes. There is very little known on the effect of impaired N-glycosylation on the hypothalamic-pituitary-adrenal axis function and whether CDG patients are at risk of secondary adrenal insufficiency and decreased adrenal cortisol production. Cortisol and ACTH concentrations were simultaneously measured between 7:44 am to 1 pm in forty-three subjects (20 female, median age 12.8 years, range 0.1 to 48.6 years) participating in an ongoing international, multi-center Natural History study for PMM2-CDG (ClinicalTrials.gov Identifier: NCT03173300). Of the 43 subjects, 11 (25.6%) had cortisol below 5 μg/dl and low to normal ACTH levels, suggestive of secondary adrenal insufficiency. Two of the 11 subjects have confirmed central adrenal insufficiency and are on hydrocortisone replacement and/or stress dosing during illness; 3 had normal and 1 had subnormal cortisol response to ACTH low-dose stimulation test but has not yet been started on therapy; the remaining 5 have upcoming stimulation testing planned. Our findings suggest that patients with PMM2-CDG may be at risk for adrenal insufficiency. Monitoring of morning cortisol and ACTH levels should be part of the standard care in patients with PMM2-CDG.

[13C]-galactose breath test in a patient with galactokinase deficiency and spastic diparesis

Galactokinase deficiency is an inborn error of carbohydrate metabolism due to a block in the formation of galactose-1-phosphate from galactose. Although the association of galactokinase deficiency with formation of cataracts is well established, the extent of the clinical phenotype is still under investigation. We describe a 6-year-old female who was diagnosed with galactokinase deficiency due to cataract formation when she was 10 months of age and initially started on galactose-restricted diet at that time for 5 months. She developed gait abnormality at 4 years of age. Breath tests via measurement of 13C isotope in exhaled carbon dioxide following 13C-labeled galactose administration at carbon-1 and carbon-2 positions revealed oxidation rates within the normal range. The results in this patient strikingly contrast with the results of another patient with GALK1 deficiency that underwent breath testing with [1-14C]-galactose and [2-14C]-galactose. Extension of in vivo breath tests to other galactokinase patients is needed to better understand the pathophysiology of this disease.

Transforming the clinical outcome in CRIM-negative infantile Pompe disease identified via newborn screening: the benefits of early treatment with enzyme replacement therapy and immune tolerance induction

Purpose:

To assess the magnitude of benefit to early treatment initiation, enabled by newborn screening or prenatal diagnosis, in patients with cross-reactive immunological material (CRIM)-negative infantile Pompe disease (IPD), treated with enzyme replacement therapy (ERT) and prophylactic immune tolerance induction (ITI) with rituximab, methotrexate, and IVIG.

Methods:

A total of 41 CRIM-negative IPD patients were evaluated. Amongst patients who were treated with ERT+ITI (n=30), those who were invasive ventilator-free at baseline and had ≥6 months of follow-up were stratified based on age at treatment initiation: 1) early (≤4 weeks), 2) intermediate (>4 and ≤15 weeks), and 3) late (>15 weeks). A historical cohort of 11 CRIM-negative patients with IPD treated with ERT monotherapy served as an additional comparator group.

Results:

Twenty patients were included; five, seven, and eight in early, intermediate, and late treatment groups, respectively. Genotypes were similar across the three groups. Early-treated patients showed significant improvements in left ventricular mass index, motor and pulmonary outcomes, as well as biomarkers creatine kinase and urinary glucose tetrasaccharide, compared to those treated later.

Conclusion:

Our preliminary data suggest that early treatment with ERT+ITI can transform the long-term CRIM-negative IPD phenotype, which represents the most severe end of the Pompe disease spectrum.

Mutations in the V-ATPase Assembly Factor VMA21 Cause a Congenital Disorder of Glycosylation With Autophagic Liver Disease

BACKGROUND AND AIMS

Vacuolar H+-ATP complex (V-ATPase) is a multisubunit protein complex required for acidification of intracellular compartments. At least five different factors are known to be essential for its assembly in the endoplasmic reticulum (ER). Genetic defects in four of these V-ATPase assembly factors show overlapping clinical features, including steatotic liver disease and mild hypercholesterolemia. An exception is the assembly factor vacuolar ATPase assembly integral membrane protein (VMA21), whose X-linked mutations lead to autophagic myopathy.

APPROACH AND RESULTS

Here, we report pathogenic variants in VMA21 in male patients with abnormal protein glycosylation that result in mild cholestasis, chronic elevation of aminotransferases, elevation of (low-density lipoprotein) cholesterol and steatosis in hepatocytes. We also show that the VMA21 variants lead to V-ATPase misassembly and dysfunction. As a consequence, lysosomal acidification and degradation of phagocytosed materials are impaired, causing lipid droplet (LD) accumulation in autolysosomes. Moreover, VMA21 deficiency triggers ER stress and sequestration of unesterified cholesterol in lysosomes, thereby activating the sterol response element-binding protein-mediated cholesterol synthesis pathways.

CONCLUSIONS

Together, our data suggest that impaired lipophagy, ER stress, and increased cholesterol synthesis lead to LD accumulation and hepatic steatosis. V-ATPase assembly defects are thus a form of hereditary liver disease with implications for the pathogenesis of nonalcoholic fatty liver disease.

Diagnostic journey and impact of enzyme replacement therapy for mucopolysaccharidosis IVA: a sibling control study

Background

Mucopolysaccharidosis (MPS) IVA, also known as Morquio A syndrome, is a rare autosomal recessive lysosomal storage disorder caused by a deficiency in the enzyme N-acetylgalactosamine-6-sulfatase. Early recognition, diagnosis, and treatment of this progressive, multisystem disease by enzyme replacement therapy (ERT) can lead to improved outcomes and reduced mortality.

Methods

This report documents the diagnostic journey and treatment with ERT of three siblings with MPS IVA. Clinical outcome measures included growth, endurance, imaging, cardiac, respiratory, ophthalmology, and laboratory evaluations.

Results

Three siblings, diagnosed at 14.7, 10.1, and 3.2 years of age, demonstrated clinical improvement with weekly infusions of 2.0 mg/kg elosulfase alfa (Vimizim^®, BioMarin Pharmaceutical, Novato, CA, USA). Patient 1 (oldest sibling) and Patient 2 (middle sibling) experienced a diagnostic delay of 8 years 7 months and 4 years after symptom onset, respectively. All three patients demonstrated improvements in growth, 6-min walk distance, joint range of motion, and respiratory function after 30 months of ERT. The treatment was well tolerated without any adverse events.

Conclusions

This case series highlights the importance of early recognition of the clinical and imaging findings that are initially subtle in MPS IVA. Early treatment with ERT is necessary to slow irreversible disease progression and improve patient outcomes. The oldest sibling experienced improvements in mobility despite severe symptoms resulting from a late diagnosis. When evaluating patients with skeletal anomalies, imaging multiple body regions is recommended. When findings such as anterior beaking of vertebrae or bilateral femoral head dysplasia are present, MPS IVA should be included in the differential diagnosis. Newborn screening must be considered for early detection, accurate diagnosis, and initiation of treatment to reduce morbidity.

Person Ability Scores as an Alternative to Norm-Referenced Scores as Outcome Measures in Studies of Neurodevelopmental Disorders

Although norm-referenced scores are essential to the identification of disability, they possess several features which affect their sensitivity to change. Norm-referenced scores often decrease over time among people with neurodevelopmental disorders who exhibit slower-than-average increases in ability. Further, the reliability of norm-referenced scores is lower at the tails of the distribution, resulting in floor effects and increased measurement error for people with neurodevelopmental disorders. In contrast, the person ability scores generated during the process of constructing a standardized test with item response theory are designed to assess change. We illustrate these limitations of norm-referenced scores, and relative advantages of ability scores, using data from studies of autism spectrum disorder and creatine transporter deficiency.

Galactokinase deficiency: lessons from the GalNet registry

PURPOSE

Galactokinase (GALK1) deficiency is a rare hereditary galactose metabolism disorder. Beyond cataract, the phenotypic spectrum is questionable. Data from affected patients included in the Galactosemias Network registry were collected to better characterize the phenotype.

METHODS

Observational study collecting medical data of 53 not previously reported GALK1 deficient patients from 17 centers in 11 countries from December 2014 to April 2020.

RESULTS

Neonatal or childhood cataract was reported in 15 and 4 patients respectively. The occurrence of neonatal hypoglycemia and infection were comparable with the general population, whereas bleeding diathesis (8.1% versus 2.17-5.9%) and encephalopathy (3.9% versus 0.3%) were reported more often. Elevated transaminases were seen in 25.5%. Cognitive delay was reported in 5 patients. Urinary galactitol was elevated in all patients at diagnosis; five showed unexpected Gal-1-P increase. Most patients showed enzyme activities ≤1%. Eleven different genotypes were described, including six unpublished variants. The majority was homozygous for NM_000154.1:c.82C>A (p.Pro28Thr). Thirty-five patients were diagnosed following newborn screening, which was clearly beneficial.

CONCLUSION

The phenotype of GALK1 deficiency may include neonatal elevation of transaminases, bleeding diathesis, and encephalopathy in addition to cataract. Potential complications beyond the neonatal period are not systematically surveyed and a better delineation is needed.

The Importance of Succinylacetone: Tyrosinemia Type I Presenting with Hyperinsulinism and Multiorgan Failure Following Normal Newborn Screening

Tyrosinemia type 1 (TT1) is an inborn error of tyrosine metabolism with features including liver dysfunction, cirrhosis, and hepatocellular carcinoma; renal dysfunction that may lead to failure to thrive and bone disease; and porphyric crises. Once fatal in most infantile-onset cases, pre-symptomatic diagnosis through newborn screening (NBS) protocols, dietary management, and pharmacotherapy with nitisinone have improved outcomes. Succinylacetone provides a sensitive and specific marker for the detection of TT1 but is not universally utilized in screening protocols for the disease. Here, we report an infant transferred to our facility for evaluation and management of hyperinsulinism who subsequently developed acute-onset liver, respiratory, and renal failure around one month of life. She was found to have TT1 caused by novel pathogenic variant in fumarylacetoacetate hydrolase (c.1014 delC, p.Cys 338 Ter). Her NBS, which utilized tyrosine as a primary marker, had been reported as normal, with a tyrosine level of 151 μmol/L (reference: < 280 μmol/L). Retrospective analysis of dried blood spot samples via tandem mass spectrometry showed detectable succinylacetone ranging 4.65-10.34 μmol/L. To our knowledge, this is the first patient with TT1 whose initial presenting symptom was hyperinsulinemic hypoglycemia. The case highlights the importance of maintaining a high suspicion for metabolic disease in critically ill children, despite normal NBS. We also use the case to advocate for NBS for TT1 using succinylacetone quantitation.

Persistent dyslipidemia in treatment of lysosomal acid lipase deficiency

BACKGROUND

Lysosomal acid lipase deficiency (LALD) is an autosomal recessive inborn error of lipid metabolism characterized by impaired lysosomal hydrolysis and consequent accumulation of cholesteryl esters and triglycerides. The phenotypic spectrum is diverse, ranging from severe, neonatal onset failure to thrive, hepatomegaly, hepatic fibrosis, malabsorption and adrenal insufficiency to childhood-onset hyperlipidemia, hepatomegaly, and hepatic fibrosis. Sebelipase alfa enzyme replacement has been approved by the Food and Drug Administration for use in LALD after demonstrating dramatic improvement in transaminitis and dyslipidemia with initiation of enzyme replacement therapy.

METHODS

A chart review was performed on 2 patients with childhood-onset, symptomatic LALD with persistent dyslipidemia despite appropriate enzyme replacement therapy to identify biological pathways and risk factors for incomplete response to therapy.

RESULTS

Two patients with attenuated, symptomatic LALD had resolution of transaminitis on enzyme replacement therapy without concomitant effect on dyslipidemia despite dose escalation and no evidence of antibody response to enzyme.

CONCLUSION

Enzyme replacement therapy does not universally resolve all complications of LALD. Persistent dyslipidemia remains a clinically significant issue, likely related to the complex metabolic pathways implicated in LALD pathogenesis. We discuss the possible mechanistic basis for this unexpected finding and the implications for curative LALD therapy.

Gaucher disease status and treatment assessment: pilot study using magnetic resonance spectroscopy bone marrow fat fractions in pediatric patients

OBJECTIVE

To assess magnetic resonance spectroscopy (MRS) bone marrow fat fractions' ability to discern between untreated Gaucher disease patients and healthy controls based on assessment of bone marrow infiltration and evaluate response to enzyme replacement therapy (ERT) on serial imaging.

METHODS

This retrospective case-controlled study compared conventional MRI and bone marrow MRS findings in six pediatric and young adult Gaucher disease patients with age- and sex-matched controls, examining femoral neck and lumbar spine bone marrow fat fractions and bone marrow burden (BMB) scores. Separate analysis of six patients with serial imaging on ERT was performed with analysis of fat fractions, BMB scores, organ volumes, and serum chitotriosidase.

RESULTS

Untreated patients had significantly lower femoral and lumbar spine fat fractions than controls (0.32 versus 0.67, p = 0.041 and 0.17 versus 0.34, p = 0.041, respectively). Total BMB scores were significantly higher in patients (8.0 versus 3.5, p = 0.015). In patients on ERT with average follow-up of 3.5 years, femoral neck fat fraction was the sole significant predictor of treatment duration (R square: 0.804, p < 0.001) when adjusted for age. Femoral neck fat fraction also correlated with lumbar spine fat fraction, liver volume and chitotriosidase (p < 0.05). MRS test-retest reliability was excellent (Pearson correlations: 0.96, 0.99; p-values <0.001). BMB inter-rater reliability was good overall with an intra-class correlation coefficient of 0.79 for total score, although lumbar spine score reliability was poor at 0.45.

CONCLUSION

MRS-derived bone marrow fat fractions appear capable of detecting Gaucher disease severity and monitoring treatment-related changes as a predictor of ERT duration in pediatric and young adult patients.

Serial Magnetic Resonance Imaging (MRI) in Pyruvate Dehydrogenase Complex Deficiency

OBJECTIVES

To report 2 additional cases of pyruvate dehydrogenase complex deficiency with reversible deep gray matter lesions following initiation of ketogenic diet and to perform a literature review of serial imaging in patients with pyruvate dehydrogenase complex.

METHODS

Clinical data on 3 previously unpublished cases of patients with pyruvate dehydrogenase complex deficiency and with serial magnetic resonance imagings (MRIs) before and after institution of ketogenic diet were reported. A systematic literature review was performed to search for published cases of patients with confirmed pyruvate dehydrogenase complex deficiency who underwent serial MRIs.

RESULTS

The 3 subjects in this series demonstrated clinical improvement on ketogenic diet. Two subjects showed reversal of some brain lesions on repeat MRI following initiation of ketogenic diet. Of the 21 published cases with serial MRIs, 13 patients underwent some form of treatment, and of this smaller subset 4 patients had repeat MRIs that showed definitive improvement. In both our described cases and those published in the literature, improvement occurred in lesions in the basal ganglia.

CONCLUSIONS

In patients with pyruvate dehydrogenase complex deficiency, basal ganglia lesions on MRI are reversible with treatment in some cases and could serve as a biomarker for measuring response to treatment.

Early diagnosis of infantile-onset lysosomal acid lipase deficiency in the advent of available enzyme replacement therapy

BACKGROUND

Lysosomal acid lipase deficiency (LAL-D) is an autosomal recessive disorder that can present as a severe, infantile form also known as Wolman disease. We sought to determine the outcomes and clinical needs of infants diagnosed with LAL-D, treated with enzyme replacement therapy (ERT).

METHODS

A chart review was conducted on two infantile-onset LAL-D patients to determine clinical outcomes based on laboratory results, abdominal imaging, growth and dietary records, cardiology, endocrinology, ophthalmology, hematology, and neurocognitive evaluations.

RESULTS

Two patients, both diagnosed and treated before 6 months old, demonstrated clinical improvement following weekly ERT. They required dosage increases to optimize growth and symptomatology. Both received a formula low in long chain triglycerides and high in medium chain triglycerides, an intervention that allowed significant catch-up growth. Patient 1 required treatment for partial adrenal insufficiency and hypothyroidism. Both patients demonstrated reduction in liver and spleen size and varying degrees of improved liver function. Neither experienced serious adverse reactions to ERT.

CONCLUSION

ERT has led to longer and healthier survival of affected infants. It is imperative that dietary interventions and systemic clinical care become integral to the management. Continued evidence of survival and clinical improvement in this population, coupled with available mass spectrometry enzyme assay from dried blood spots, raises the question of this rare and possibly underdiagnosed disorder's candidacy for newborn screening.

Imaging of non-neuronopathic Gaucher disease: recent advances in quantitative imaging and comprehensive assessment of disease involvement

Gaucher disease is an inherited metabolic disorder resulting in deficiency of lysosomal enzyme β-glucocerebrosidase causing the accumulation of abnormal macrophages (“Gaucher cells”) within multiple organs, most conspicuously affecting the liver, spleen, and bone marrow. As the most common glycolipid metabolism disorder, it is important for radiologists encountering these patients to be familiar with advances in imaging of organ and bone marrow involvement and understand the role of imaging in clinical decision-making. The recent advent of commercially available, reliable, and reproducible quantitative MRI acquisitions to measure fat fractions prompts revisiting the role of quantitative assessment of bone marrow involvement. This manuscript reviews the diverse imaging manifestations of Gaucher disease and discusses more optimal quantitative approaches to ascertain solid organ and bone marrow involvement with an emphasis on future applications of other quantitative methods including elastography.

Biomarkers of oxidative stress, inflammation, and vascular dysfunction in inherited cystathionine β-synthase deficient homocystinuria and the impact of taurine treatment in a phase 1/2 human clinical trial

STUDY OBJECTIVE

A phase 1/2 clinical trial was performed in individuals with cystathionine β synthase (CBS) deficient homocystinuria with aims to: (a) assess pharmacokinetics and safety of taurine therapy, (b) evaluate oxidative stress, inflammation, and vascular function in CBS deficiency, and (c) evaluate the impact of short-term taurine treatment.

METHODS

Individuals with pyridoxine-nonresponsive CBS deficiency with homocysteine >50 μM, without inflammatory disorder or on antioxidant therapy were enrolled. Biomarkers of oxidative stress and inflammation, endothelial function (brachial artery flow-mediated dilation [FMD]), and disease-related metabolites obtained at baseline were compared to normal values. While maintaining current treatment, patients were treated with 75 mg/kg taurine twice daily, and treatment response assessed after 4 hours and 4 days.

RESULTS

Fourteen patients (8-35 years; 8 males, 6 females) were enrolled with baseline homocysteine levels 161 ± 67 μM. The study found high-dose taurine to be safe when excluding preexisting hypertriglyceridemia. Taurine pharmacokinetics showed a rapid peak level returning to near normal levels at 12 hours, but had slow accumulation and elevated predosing levels after 4 days of treatment. Only a single parameter of oxidative stress, 2,3-dinor-8-isoprostaglandin-F2α, was elevated at baseline, with no elevated inflammatory parameters, and no change in FMD values overall. Taurine had no effect on any of these parameters. However, the effect of taurine was strongly related to pretreatment FMD values; and taurine significantly improved FMD in the subset of individuals with pretreatment FMD values <10% and in individuals with homocysteine levels >125 μM, pertinent to endothelial function.

CONCLUSION

Taurine improves endothelial function in CBS-deficient homocystinuria in patients with preexisting reduced function.

Early Indicators of Creatine Transporter Deficiency

Early identification is a goal for creatine transporter deficiency and will be critical for future treatment. Before their first birthday, one-half of this sample showed both a significant feeding/weight gain issue and delayed sitting or crawling. Combined, these early indicators could have alerted providers to conduct a urine screen.

Phenotype, treatment practice and outcome in the cobalamin-dependent remethylation disorders and MTHFR deficiency: Data from the E-HOD registry

AIM

To explore the clinical presentation, course, treatment and impact of early treatment in patients with remethylation disorders from the European Network and Registry for Homocystinurias and Methylation Defects (E-HOD) international web-based registry.

RESULTS

This review comprises 238 patients (cobalamin C defect n = 161; methylenetetrahydrofolate reductase deficiency n = 50; cobalamin G defect n = 11; cobalamin E defect n = 10; cobalamin D defect n = 5; and cobalamin J defect n = 1) from 47 centres for whom the E-HOD registry includes, as a minimum, data on medical history and enrolment visit. The duration of observation was 127 patient years. In 181 clinically diagnosed patients, the median age at presentation was 30 days (range 1 day to 42 years) and the median age at diagnosis was 3.7 months (range 3 days to 56 years). Seventy-five percent of pre-clinically diagnosed patients with cobalamin C disease became symptomatic within the first 15 days of life. Total homocysteine (tHcy), amino acids and urinary methylmalonic acid (MMA) were the most frequently assessed disease markers; confirmatory diagnostics were mainly molecular genetic studies. Remethylation disorders are multisystem diseases dominated by neurological and eye disease and failure to thrive. In this cohort, mortality, thromboembolic, psychiatric and renal disease were rarer than reported elsewhere. Early treatment correlates with lower overall morbidity but is less effective in preventing eye disease and cognitive impairment. The wide variation in treatment hampers the evaluation of particular therapeutic modalities.

CONCLUSION

Treatment improves the clinical course of remethylation disorders and reduces morbidity, especially if started early, but neurocognitive and eye symptoms are less responsive. Current treatment is highly variable. This study has the inevitable limitations of a retrospective, registry-based design.

Increased Clinical Sensitivity and Specificity of Plasma Protein N-Glycan Profiling for Diagnosing Congenital Disorders of Glycosylation by Use of Flow Injection-Electrospray Ionization-Quadrupole Time-of-Flight Mass Spectrometry

BACKGROUND

Congenital disorders of glycosylation (CDG) represent 1 of the largest groups of metabolic disorders with >130 subtypes identified to date. The majority of CDG subtypes are disorders of N-linked glycosylation, in which carbohydrate residues, namely, N-glycans, are posttranslationally linked to asparagine molecules in peptides. To improve the diagnostic capability for CDG, we developed and validated a plasma N-glycan assay using flow injection-electrospray ionization-quadrupole time-of-flight mass spectrometry.

METHODS

After PNGase F digestion of plasma glycoproteins, N-glycans were linked to a quinolone using a transient amine group at the reducing end, isolated by a hydrophilic interaction chromatography column, and then identified by accurate mass and quantified using a stable isotope-labeled glycopeptide as the internal standard.

RESULTS

This assay differed from other N-glycan profiling methods because it was free of any contamination from circulating free glycans and was semiquantitative. The low end of the detection range tested was at 63 nmol/L for disialo-biantennary N-glycan. The majority of N-glycans in normal plasma had <1% abundance. Abnormal N-glycan profiles from 19 patients with known diagnoses of 11 different CDG subtypes were generated, some of which had previously been reported to have normal N-linked protein glycosylation by carbohydrate-deficient transferrin analysis.

CONCLUSIONS

The clinical specificity and sensitivity of N-glycan analysis was much improved with this method. Additional CDGs can be diagnosed that would be missed by carbohydrate-deficient transferrin analysis. The assay provides novel biomarkers with diagnostic and potentially therapeutic significance.

Characteristics and outcomes of patients with formiminoglutamic aciduria detected through newborn screening

BACKGROUND

Glutamate formiminotransferase deficiency (FTCD deficiency) or formiminoglutamic aciduria is the second most common of the known inherited disorders of folate metabolism. Initial case reports suggested that patients may have severe intellectual disability and megaloblastic anemia. However, these cases were obtained from screening cohorts of patients with developmental delay. Subsequently, patients with milder clinical phenotypes have been reported. The full phenotypic spectrum of this disorder remains unknown.

METHODS

In many states, FTCD deficiency can be incidentally detected on tandem mass spectrometry-based newborn screening of dried blood spots. In this work, we report the outcomes of infants identified to have FTCD deficiency through newborn screening.

RESULTS

During the study period, 18 patients were identified to have FTCD deficiency and were referred and evaluated at one of the two participating metabolic centers. The overall rate of FTCD deficiency detected through the New Jersey screening program over the study time period was 1:58,982. At a mean age of 56 months at last follow-up: 3/18 (16%) had developmental delays requiring individualized education plans, no patients had profound intellectual disability; 4/16 (25%) had mild self-limited anemia, no patients had profound anemia.

CONCLUSIONS

These data suggest that the majority of individuals with FTCD deficiency detected by newborn screening are asymptomatic.

Conducting an investigator-initiated randomized double-blinded intervention trial in acute decompensation of inborn errors of metabolism: Lessons from the N-Carbamylglutamate Consortium

Organic acidemias and urea cycle disorders are ultra-rare inborn errors of metabolism characterized by episodic acute decompensation, often associated with hyperammonemia, resulting in brain edema and encephalopathy. Retrospective reports and translational studies suggest that N-carbamylglutamate (NCG) may be effective in reducing ammonia levels during acute decompensation in two organic acidemias, propionic and methylmalonic acidemia (PA and MMA), and in two urea cycle disorders, carbamylphosphate synthetase 1 and ornithine transcarbamylase deficiency (CPSD and OTCD). We established the 9-site N-carbamylglutamate Consortium (NCGC) in order to conduct two randomized double-blind, placebo-controlled trials of NCG in acute hyperammonemia of PA, MMA, CPSD and OTCD. Conducting clinical trials is challenging in any disease, but poses unique barriers and risks in the ultra-rare disorders. As the number of clinical trials in orphan diseases increases, evaluating the successes and opportunities for improvement in such trials is essential. We summarize herein the design, methods, experiences, challenges and lessons from the NCGC-conducted trials.

Pharmacokinetics of glycerol phenylbutyrate in pediatric patients 2 months to 2 years of age with urea cycle disorders

INTRODUCTION

Glycerol phenylbutyrate (GPB) is approved in the US and EU for the chronic management of patients ≥2 months of age with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. GPB is a pre-prodrug, hydrolyzed by lipases to phenylbutyric acid (PBA) that upon absorption is beta-oxidized to the active nitrogen scavenger phenylacetic acid (PAA), which is conjugated to glutamine (PAGN) and excreted as urinary PAGN (UPAGN). Pharmacokinetics (PK) of GPB were examined to see if hydrolysis is impaired in very young patients who may lack lipase activity.

METHODS

Patients 2 months to <2 years of age with UCDs from two open label studies (n = 17, median age 10 months) predominantly on stable doses of nitrogen scavengers (n = 14) were switched to GPB. Primary assessments included traditional plasma PK analyses of PBA, PAA, and PAGN, using noncompartmental methods with WinNonlin™. UPAGN was collected periodically throughout the study up to 12 months.

RESULTS

PBA, PAA and PAGN rapidly appeared in plasma after GPB dosing, demonstrating evidence of GPB cleavage with subsequent PBA absorption. Median concentrations of PBA, PAA and PAGN did not increase over time and were similar to or lower than the values observed in older UCD patients. The median PAA/PAGN ratio was well below one over time, demonstrating that conjugation of PAA with glutamine to form PAGN did not reach saturation. Covariate analyses indicated that age did not influence the PK parameters, with body surface area (BSA) being the most significant covariate, reinforcing current BSA based dosing recommendations as seen in older patients.

CONCLUSION

These observations demonstrate that UCD patients aged 2 months to <2 years have sufficient lipase activity to adequately convert the pre-prodrug GPB to PBA. PBA is then converted to its active moiety (PAA) providing successful nitrogen scavenging even in very young children.

TANGO2: expanding the clinical phenotype and spectrum of pathogenic variants

Purpose

TANGO2-related disorders were first described in 2016 and prior to this publication, only 15 individuals with TANGO2-related disorder were described in the literature. Primary features include metabolic crisis with rhabdomyolysis, encephalopathy, intellectual disability, seizures, and cardiac arrhythmias. We assess whether genotype and phenotype of TANGO2-related disorder has expanded since the initial discovery and determine the efficacy of exome sequencing (ES) as a diagnostic tool for detecting variants.

Methods

We present a series of 14 individuals from 11 unrelated families with complex medical and developmental histories, in whom ES or microarray identified compound heterozygous or homozygous variants in TANGO2.

Results

The initial presentation of patients with TANGO2-related disorders can be variable, including primarily neurological presentations. We expand the phenotype and genotype for TANGO2, highlighting the variability of the disorder.

Conclusion

TANGO2-related disorders can have a more diverse clinical presentation than previously anticipated. We illustrate the utility of routine ES data reanalysis whereby discovery of novel disease genes can lead to a diagnosis in previously unsolved cases and the need for additional copy-number variation analysis when ES is performed.

Failure to Thrive: An Expanded Differential Diagnosis

The patient is a term 6-month-old male, who presented with failure to thrive since birth. History was remarkable for suspected milk and soy protein allergy, gastroesophageal reflux, constipation, and abdominal distension that was present since birth. He was losing weight despite oral intake of over 100 kcal/kg per day. Prior workup including laboratory studies, abdominal X-ray, upper gastrointestinal series with fluoroscopy, barium enema, and abdominal ultrasound were all within normal limits. The patient's history, diagnostic evaluation, and final diagnosis are revealed. This case highlights a rare condition presenting as failure to thrive, a common problem with a wide differential diagnosis.

Treatment outcome of creatine transporter deficiency: international retrospective cohort study

To evaluate the outcome of current treatment for creatine transporter (CRTR) deficiency, we developed a clinical severity score and initiated an international treatment registry. An online questionnaire was completed by physicians following patients with CRTR deficiency on a treatment, including creatine and/or arginine, and/or glycine. Clinical severity score included 1) global developmental delay/intellectual disability; 2) seizures; 3) behavioural disorder. Phenotype scored 1-3 = mild; 4-6 = moderate; and 7-9 = severe. We applied the clinical severity score pre- and on-treatment. Seventeen patients, 14 males and 3 females, from 16 families were included. Four patients had severe, 6 patients had moderate, and 7 patients had a mild phenotype. The phenotype ranged from mild to severe in patients diagnosed at or before 2 years of age or older than 6 years of age. The phenotype ranged from mild to severe in patients with mildly elevated urine creatine to creatinine ratio. Fourteen patients were on the combined creatine, arginine and glycine therapy. On the combined treatment with creatine, arginine and glycine, none of the males showed either deterioration or improvements in their clinical severity score, whereas two females showed improvements in the clinical severity score. Creatine monotherapy resulted in deterioration of the clinical severity score in one male. There seems to be no correlation between phenotype and degree of elevation in urine creatine to creatinine ratio, genotype, or age at diagnosis. Combined creatine, arginine and glycine therapy might have stopped disease progression in males and improved phenotype in females.

Complex care of individuals with multiple sulfatase deficiency: Clinical cases and consensus statement

Multiple sulfatase deficiency (MSD) is an ultra-rare neurodegenerative disorder that results in defective sulfatase post-translational modification. Sulfatases in the body are activated by a unique protein, formylglycine-generating enzyme (FGE) that is encoded by SUMF1. When FGE is absent or insufficient, all 17 known human sulfatases are affected, including the enzymes associated with metachromatic leukodystrophy (MLD), several mucopolysaccharidoses (MPS II, IIIA, IIID, IVA, VI), chondrodysplasia punctata, and X-linked ichthyosis. As such, individuals demonstrate a complex and severe clinical phenotype that has not been fully characterized to date. In this report, we describe two individuals with distinct clinical presentations of MSD. Also, we detail a comprehensive systems-based approach to the management of individuals with MSD, from the initial diagnostic evaluation to unique multisystem issues and potential management options. As there have been no natural history studies to date, the recommendations within this report are based on published studies and consensus opinion and underscore the need for future research on evidence-based outcomes to improve management of children with MSD.

Publisher Correction: A PRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients

The original version of this Article contained an error in the title, which was incorrectly given as 'APRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients'. This has now been corrected in both the PDF and HTML versions of the Article to read 'A PRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients'.

Consensus guidelines for newborn screening, diagnosis and treatment of infantile Krabbe disease

BACKGROUND

Krabbe disease is a rare neurodegenerative genetic disorder caused by deficiency of galactocerebrosidase. Patients with the infantile form of Krabbe disease can be treated at a presymptomatic stage with human stem cell transplantation which improves survival and clinical outcomes. However, without a family history, most cases of infantile Krabbe disease present after onset of symptoms and are ineligible for transplantation. In 2006, New York began screening newborns for Krabbe disease to identify presymptomatic cases. To ensure that those identified with infantile disease received timely treatment, New York public health and medical systems took steps to accurately diagnose and rapidly refer infants for human stem cell transplantation within the first few weeks of life. After 11 years of active screening in New York and the introduction of Krabbe disease newborn screening in other states, new information has been gained which can inform the design of newborn screening programs to improve infantile Krabbe disease outcomes.

FINDINGS

Recent information relevant to Krabbe disease screening, diagnosis, and treatment were assessed by a diverse group of public health, medical, and advocacy professionals. Outcomes after newborn screening may improve if treatment for infantile disease is initiated before 30 days of life. Newer laboratory screening and diagnostic tools can improve the speed and specificity of diagnosis and help facilitate this early referral. Given the rarity of Krabbe disease, most recommendations were based on case series or expert opinion.

CONCLUSION

This report updates recommendations for Krabbe disease newborn screening to improve the timeliness of diagnosis and treatment of infantile Krabbe disease. In the United States, several states have begun or are considering Krabbe disease newborn screening. These recommendations can guide public health laboratories on methodologies for screening and inform clinicians about the need to promptly diagnose and treat infantile Krabbe disease. The timing of the initial referral after newborn screening, the speed of diagnostic confirmation of infantile disease, and the transplantation center's experience and ability to rapidly respond to a suspected patient with newly diagnosed infantile Krabbe disease are critical for optimal outcomes.

APRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients

To date, epimutations reported in man have been somatic and erased in germlines. Here, we identify a cause of the autosomal recessive cblC class of inborn errors of vitamin B₁₂ metabolism that we name “epi-cblC”. The subjects are compound heterozygotes for a genetic mutation and for a promoter epimutation, detected in blood, fibroblasts, and sperm, at the MMACHC locus; 5-azacytidine restores the expression of MMACHC in fibroblasts. MMACHC is flanked by CCDC163P and PRDX1, which are in the opposite orientation. The epimutation is present in three generations and results from PRDX1 mutations that force antisense transcription of MMACHC thereby possibly generating a H3K36me3 mark. The silencing of PRDX1 transcription leads to partial hypomethylation of the epiallele and restores the expression of MMACHC. This example of epi-cblC demonstrates the need to search for compound epigenetic-genetic heterozygosity in patients with typical disease manifestation and genetic heterozygosity in disease-causing genes located in other gene trios.

Inborn errors of vitamin B₁₂ metabolism of the cblC class are caused by mutations in the MMACHC gene. Here, Guéant et al. report epi-cblC, a class of cblC in which patients are compound heterozygous for a genetic mutation and a secondary epimutation at the MMACHC locus.

Intrafamilial variability in the clinical manifestations of mucopolysaccharidosis type II: Data from the Hunter Outcome Survey (HOS)

Several cases of phenotypic variability among family members with mucopolysaccharidosis type II (MPS II) have been reported, but the data are limited. Data from patients enrolled in the Hunter Outcome Survey (HOS) were used to investigate intrafamilial variability in male siblings with MPS II. As of July 2015, data were available for 78 patients aged ≥5 years at last visit who had at least one affected sibling (39 sibling pairs). These patients were followed prospectively (i.e., they were alive at enrollment in HOS). The median age at the onset of signs and symptoms was the same for the elder and younger brothers (2.0 years); however, the younger brothers were typically diagnosed at a younger age than the elder brothers (median age, 2.5 and 5.1 years, respectively). Of the 39 pairs, eight pairs were classified as being discordant (the status of four or more signs and symptoms differed between the siblings); 21 pairs had one, two, or three signs and symptoms that differed between the siblings, and 10 pairs had none. Regression status of the majority of the developmental milestones studied was generally concordant among siblings. Functional classification, a measure of central nervous system involvement, was the same in 24/28 pairs, although four pairs were considered discordant as functional classification differed between the siblings. Overall, this analysis revealed similarity in the clinical manifestations of MPS II among siblings. This information should help to improve our understanding of the clinical presentation of the disease, including phenotype prediction in affected family members.

New tools and approaches to newborn screening: ready to open Pandora's box?

The landscape of newborn screening (NBS) is changing as new tools are developed. We must acknowledge that NBS is a very important and extraordinarily positive initiative especially for rare and serious inherited disorders; however, lessons learned from current NBS should guide the future of NBS as we enter the era of “omics” that will expand NBS for many other genetic disorders. In this article, I will first discuss new tools such as genomics and metabolomics for NBS. I will then turn to assessing how best to take advantage of new technical developments while considering the best interests of patients and the success of newborn screening.

Safety and efficacy of glycerol phenylbutyrate for management of urea cycle disorders in patients aged 2months to 2years

INTRODUCTION

Glycerol phenylbutyrate (GPB) is approved in the US for the management of patients 2months of age and older with urea cycle disorders (UCDs) that cannot be managed with protein restriction and/or amino acid supplementation alone. Limited data exist on the use of nitrogen conjugation agents in very young patients.

METHODS

Seventeen patients (15 previously on other nitrogen scavengers) with all types of UCDs aged 2months to 2years were switched to, or started, GPB. Retrospective data up to 12months pre-switch and prospective data during initiation of therapy were used as baseline measures. The primary efficacy endpoint of the integrated analysis was the successful transition to GPB with controlled ammonia (<100μmol/L and no clinical symptoms). Secondary endpoints included glutamine and levels of other amino acids. Safety endpoints included adverse events, hyperammonemic crises (HACs), and growth and development.

RESULTS

82% and 53% of patients completed 3 and 6months of therapy, respectively (mean 8.85months, range 6days-18.4months). Patients transitioned to GPB maintained excellent control of ammonia and glutamine levels. There were 36 HACs in 11 patients before GPB and 11 in 7 patients while on GPB, with a reduction from 2.98 to 0.88 episodes per year. Adverse events occurring in at least 10% of patients while on GPB were neutropenia, vomiting, diarrhea, pyrexia, hypophagia, cough, nasal congestion, rhinorrhea, rash/papule.

CONCLUSION

GPB was safe and effective in UCD patients aged 2months to 2years. GPB use was associated with good short- and long-term control of ammonia and glutamine levels, and the annualized frequency of hyperammonemic crises was lower during the study than before the study. There was no evidence for any previously unknown toxicity of GPB.

Utility of Genetic Testing for Confirmation of Abnormal Newborn Screening in Disorders of Long-Chain Fatty Acids: A Missed Case of Carnitine Palmitoyltransferase 1A (CPT1A) Deficiency

An 18-month-old male was evaluated after presenting with disproportionately elevated liver transaminases in the setting of acute gastroenteritis. He had marked hepatomegaly on physical exam that was later confirmed with an abdominal ultrasound. Given this clinical picture, suspicion for a fatty acid oxidation disorder was raised. Further investigation revealed that his initial newborn screen was positive for carnitine palmitoyltransferase 1A (CPT1A) deficiency-a rare autosomal recessive disorder of long-chain fatty acid oxidation. Confirmatory biochemical testing in the newborn period showed carnitine levels to be unexpectedly low with a normal acylcarnitine profile. Thus, it was considered to be a false-positive newborn screen and metabolic follow-up was not recommended. Repeat biochemical testing during this hospitalization revealed a normal acylcarnitine profile. The only abnormalities noted were a low proportion of acylcarnitine species from plasma, an elevated free-to-total carnitine ratio, and mild hypoketotic medium chain dicarboxylic aciduria on urine organic acids. Gene sequencing of CPT1A revealed a novel homozygous splice site variant that confirmed his diagnosis. CPT1A deficiency has a population founder effect in the Inuit and other Arctic groups, but has not been previously reported in persons of Ashkenazi Jewish ancestry.

FBXL4 defects are common in patients with congenital lactic acidemia and encephalomyopathic mitochondrial DNA depletion syndrome

Mutations in FBXL4 have recently been recognized to cause a mitochondrial disorder, with clinical features including early onset lactic acidosis, hypotonia, and developmental delay. FBXL4 sequence analysis was performed in 808 subjects suspected to have a mitochondrial disorder. In addition, 28 samples from patients with early onset of lactic acidosis, but without identifiable mutations in 192 genes known to cause mitochondrial diseases, were examined for FBXL4 mutations. Definitive diagnosis was made in 10 new subjects with a total of 7 novel deleterious variants; 5 null and 2 missense substitutions. All patients exhibited congenital lactic acidemia, most of them with severe encephalopathic presentation, and global developmental delay. Overall, FBXL4 defects account for at least 0.7% (6 out of 808) of subjects suspected to have a mitochondrial disorder, and as high as 14.3% (4 out of 28) in young children with congenital lactic acidosis and clinical features of mitochondrial disease. Including FBLX4 in the mitochondrial diseases panel should be particularly important for patients with congenital lactic acidosis.

Argininosuccinic Acid Lyase Deficiency Missed by Newborn Screen

Argininosuccinic acid lyase (ASL) deficiency, caused by mutations in the ASL gene (OMIM: 608310) is a urea cycle disorder that has pleiotropic presentations. On the mild end, ASL deficiency can manifest as nonspecific neurocognitive abnormalities without readily identifiable signs to differentiate it from other causes of intellectual disability or learning disabilities. Dietary management and arginine supplementation, if initiated early, may ameliorate symptoms.Because of the nonspecific nature of the symptoms and the possibility for therapeutic management, ASL deficiency is part of the recommended uniform screening panel for newborn screening in the USA. We report here a case of ASL deficiency that was missed on newborn screening in the USA.The case reported here has two known pathogenic mutations - one with no residual activity and one with reported 10% residual activity. Review of this newborn screening results showed subtle elevation of citrulline, overlapping the normal range. These findings suggest that newborn screening may be missing other patients with ASL deficiency with at least one hypomorphic allele. This case was diagnosed incidentally, but in retrospect had symptoms best attributed in full or in part to his ASA deficiency, including protein aversion, developmental delay, and seizures. This case highlights the importance of considering ASL deficiency in patients with nonspecific abnormal neurocognitive signs, such as epilepsy and developmental delay, even when newborn screening was normal.

Pathogenesis and treatment of spine disease in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Skeletal disease is common in MPS patients, with the severity varying both within and between subtypes. Within the spectrum of skeletal disease, spinal manifestations are particularly prevalent. Developmental and degenerative abnormalities affecting the substructures of the spine can result in compression of the spinal cord and associated neural elements. Resulting neurological complications, including pain and paralysis, significantly reduce patient quality of life and life expectancy. Systemic therapies for MPS, such as hematopoietic stem cell transplantation and enzyme replacement therapy, have shown limited efficacy for improving spinal manifestations in patients and animal models. Therefore, there is a pressing need for new therapeutic approaches that specifically target this debilitating aspect of the disease. In this review, we examine how pathological abnormalities affecting the key substructures of the spine - the discs, vertebrae, odontoid process and dura - contribute to the progression of spinal deformity and symptomatic compression of neural elements. Specifically, we review current understanding of the underlying pathophysiology of spine disease in MPS, how the tissues of the spine respond to current clinical and experimental treatments, and discuss future strategies for improving the efficacy of these treatments.

Missed Newborn Screening Case of Carnitine Palmitoyltransferase-II Deficiency

Carnitine palmitoyltransferase-II (CPT-II) deficiency can be detected through newborn screening with tandem mass spectrometry. We report a 4-year-old patient with rhabdomyolysis due to CPT-II deficiency, which was initially missed by newborn screening. The patient presented with a 2-day history of fevers, upper respiratory infection, diffuse myalgia, and tea-colored urine. Her medical history was notable for frequent diffuse myalgia when ill. She was demonstrated to have homozygous mutation c.338C>T, p. S113L in CPT2, which is typically found in the adult-onset, myopathic form of the disease. An unknown number of CPT-II deficient patients with normal newborn screening have not yet presented to medical care with the adult-onset, myopathic form of disease. We conclude that (1) not all cases of CPT-II deficiency are currently detected through newborn screening, even when blood is appropriately collected on day 2 of life and (2) CPT-II deficiency should be kept on the differential for patients presenting with rhabdomyolysis, even if the newborn screening results were normal.

ALG1-CDG: Clinical and Molecular Characterization of 39 Unreported Patients

Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over 100 genes leading to impaired protein or lipid glycosylation. ALG1 encodes a β1,4 mannosyltransferase that catalyzes the addition of the first of nine mannose moieties to form a dolichol-lipid linked oligosaccharide intermediate required for proper N-linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1-CDG. To date 13 mutations in 18 patients from 14 families have been described with varying degrees of clinical severity. We identified and characterized 39 previously unreported cases of ALG1-CDG from 32 families and add 26 new mutations. Pathogenicity of each mutation was confirmed based on its inability to rescue impaired growth or hypoglycosylation of a standard biomarker in an alg1-deficient yeast strain. Using this approach we could not establish a rank order comparison of biomarker glycosylation and patient phenotype, but we identified mutations with a lethal outcome in the first two years of life. The recently identified protein-linked xeno-tetrasaccharide biomarker, NeuAc-Gal-GlcNAc2 , was seen in all 27 patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder.

Low bone mineral density is a common finding in patients with homocystinuria

Homocystinuria (HCU) due to deficiency of cystathionine beta-synthetase is associated with increased plasma levels of homocysteine and methionine and is characterized by developmental delay, intellectual impairment, ocular defects, thromboembolism and skeletal abnormalities. HCU has been associated with increased risk for osteoporosis in some studies, but the natural history of HCU-related bone disease is poorly understood. The objective of this study was to characterize bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DXA) in a multi-center, retrospective cohort of children and adults with HCU. We identified 19 subjects (9 males) aged 3.5 to 49.2 years who had DXA scans performed as a part of routine clinical care from 2002-2010. The mean lumbar spine (LS) BMD Z-score at the time of first DXA scan in this cohort was -1.2 (± SD of 1.3); 38% of participants had low BMD for age (as defined by a Z-score ≤-2). Homocysteine and methionine were positively associated with LS BMD Z-score in multiple linear regression models. Our findings suggest that low BMD is common in both children and adults with HCU and that routine assessment of bone health in this patient population is warranted. Future studies are needed to clarify the relationship between HCU and BMD.

ECHS1 Deficiency as a Cause of Severe Neonatal Lactic Acidosis

Mitochondrial short-chain enoyl-CoA hydratase deficiency (ECHS1D) is caused by mutations in ECHS1 (OMIM 602292) and is a recently identified inborn error of valine and fatty acid metabolism. This defect leads to secondary mitochondrial dysfunction. The majority of previously reported patients had the Leigh syndrome, with a median life expectancy of approximately 2 years. We report two siblings born 3 years apart with prenatal findings including facial dysmorphia, oligohydramnios, intrauterine growth restriction, and premature delivery. They had severe lactic acidosis with onset within the first hours of life, had congenital dilated cardiomyopathy, and died at 16 h of life and 2 days of life, respectively.Biochemical evaluation of these patients showed elevated butyryl-carnitine in the blood and elevated methylmalonyl/succinyl-CoA and decreased hydroxybutyryl-CoA in frozen liver of patient 2, confirming abnormal short-chain fatty acid metabolism. Elevated butyryl-carnitine has been reported only in a single previous case of ECHS1 deficiency, which also had neonatal onset. Pyruvate and lactate levels were both elevated with a normal pyruvate-lactate ratio. This supports the previous hypothesis that lactic acidosis in these patients results from secondary inhibition of the pyruvate dehydrogenase complex. The biomarker 2,3-dihydroxy-2-methylbutyric acid was detected in patient 2, but at lower levels than in previously reported cases.These cases extend our understanding of the severe end of the phenotypic spectrum of ECHS1 deficiency, clarify the range of biochemical abnormalities associated with this new disorder, and highlight the need to suspect this disease in patients presenting with comparable metabolic derangements and dysmorphic features.