De novo missense variants in exon 9 of SEPHS1 cause a neurodevelopmental condition with developmental delay, poor growth, hypotonia, and dysmorphic features

Selenophosphate synthetase (SEPHS) plays an essential role in selenium metabolism. Two mammalian SEPHS paralogues, SEPHS1 and SEPHS2, share high sequence identity and structural homology with SEPHS. Here, we report nine individuals from eight families with developmental delay, growth and feeding problems, hypotonia, and dysmorphic features, all with heterozygous missense variants in SEPHS1. Eight of these individuals had a recurrent variant at amino acid position 371 of SEPHS1 (p.Arg371Trp, p.Arg371Gln, and p.Arg371Gly); seven of these variants were known to be de novo. Structural modeling and biochemical assays were used to understand the effect of these variants on SEPHS1 function. We found that a variant at residue Trp352 results in local structural changes of the C-terminal region of SEPHS1 that decrease the overall thermal stability of the enzyme. In contrast, variants of a solvent-exposed residue Arg371 do not impact enzyme stability and folding but could modulate direct protein-protein interactions of SEPSH1 with cellular factors in promoting cell proliferation and development. In neuronal SH-SY5Y cells, we assessed the impact of SEPHS1 variants on cell proliferation and ROS production and investigated the mRNA expression levels of genes encoding stress-related selenoproteins. Our findings provided evidence that the identified SEPHS1 variants enhance cell proliferation by modulating ROS homeostasis. Our study supports the hypothesis that SEPHS1 plays a critical role during human development and provides a basis for further investigation into the molecular mechanisms employed by SEPHS1. Furthermore, our data suggest that variants in SEPHS1 are associated with a neurodevelopmental disorder.

SPTSSA variants alter sphingolipid synthesis and cause a complex hereditary spastic paraplegia

Sphingolipids are a diverse family of lipids with critical structural and signalling functions in the mammalian nervous system, where they are abundant in myelin membranes. Serine palmitoyltransferase, the enzyme that catalyses the rate-limiting reaction of sphingolipid synthesis, is composed of multiple subunits including an activating subunit, SPTSSA. Sphingolipids are both essential and cytotoxic and their synthesis must therefore be tightly regulated. Key to the homeostatic regulation are the ORMDL proteins that are bound to serine palmitoyltransferase and mediate feedback inhibition of enzymatic activity when sphingolipid levels become excessive. Exome sequencing identified potential disease-causing variants in SPTSSA in three children presenting with a complex form of hereditary spastic paraplegia. The effect of these variants on the catalytic activity and homeostatic regulation of serine palmitoyltransferase was investigated in human embryonic kidney cells, patient fibroblasts and Drosophila. Our results showed that two different pathogenic variants in SPTSSA caused a hereditary spastic paraplegia resulting in progressive motor disturbance with variable sensorineural hearing loss and language/cognitive dysfunction in three individuals. The variants in SPTSSA impaired the negative regulation of serine palmitoyltransferase by ORMDLs leading to excessive sphingolipid synthesis based on biochemical studies and in vivo studies in Drosophila. These findings support the pathogenicity of the SPTSSA variants and point to excessive sphingolipid synthesis due to impaired homeostatic regulation of serine palmitoyltransferase as responsible for defects in early brain development and function.

Elevated oxysterol and N-palmitoyl-O-phosphocholineserine levels in congenital disorders of glycosylation

Congenital disorders of glycosylation (CDG) and Niemann-Pick type C (NPC) disease are inborn errors of metabolism that can both present with infantile-onset severe liver disease and other multisystemic manifestations. Plasma bile acid and N-palmitoyl-O-phosphocholineserine (PPCS) are screening biomarkers with proposed improved sensitivity and specificity for NPC. We report an infant with ATP6AP1-CDG who presented with cholestatic liver failure and elevated plasma oxysterols and bile acid, mimicking NPC clinically and biochemically. On further investigation, PPCS, but not the bile acid derivative N-(3β,5α,6β-trihydroxy-cholan-24-oyl) glycine (TCG), were elevated in plasma samples from individuals with ATP6AP1-, ALG1-, ALG8-, and PMM2-CDG. These findings highlight the importance of keeping CDG within the diagnostic differential when evaluating children with early onset severe liver disease and elevated bile acid or PPCS to prevent delayed diagnosis and treatment.

Bi-allelic ATG4D variants are associated with a neurodevelopmental disorder characterized by speech and motor impairment

Autophagy regulates the degradation of damaged organelles and protein aggregates, and is critical for neuronal development, homeostasis, and maintenance, yet few neurodevelopmental disorders have been associated with pathogenic variants in genes encoding autophagy-related proteins. We report three individuals from two unrelated families with a neurodevelopmental disorder characterized by speech and motor impairment, and similar facial characteristics. Rare, conserved, bi-allelic variants were identified in ATG4D, encoding one of four ATG4 cysteine proteases important for autophagosome biogenesis, a hallmark of autophagy. Autophagosome biogenesis and induction of autophagy were intact in cells from affected individuals. However, studies evaluating the predominant substrate of ATG4D, GABARAPL1, demonstrated that three of the four ATG4D patient variants functionally impair ATG4D activity. GABARAPL1 is cleaved or "primed" by ATG4D and an in vitro GABARAPL1 priming assay revealed decreased priming activity for three of the four ATG4D variants. Furthermore, a rescue experiment performed in an ATG4 tetra knockout cell line, in which all four ATG4 isoforms were knocked out by gene editing, showed decreased GABARAPL1 priming activity for the two ATG4D missense variants located in the cysteine protease domain required for priming, suggesting that these variants impair the function of ATG4D. The clinical, bioinformatic, and functional data suggest that bi-allelic loss-of-function variants in ATG4D contribute to the pathogenesis of this syndromic neurodevelopmental disorder.

Continuing a search for a diagnosis: the impact of adolescence and family dynamics

The "diagnostic odyssey" describes the process those with undiagnosed conditions undergo to identify a diagnosis. Throughout this process, families of children with undiagnosed conditions have multiple opportunities to decide whether to continue or stop their search for a diagnosis and accept the lack of a diagnostic label. Previous studies identified factors motivating a family to begin searching, but there is limited information about the decision-making process in a prolonged search and how the affected child impacts a family's decision. This study aimed to understand how families of children with undiagnosed diseases decide whether to continue to pursue a diagnosis after standard clinical testing has failed. Parents who applied to the Undiagnosed Disease Network (UDN) at the National Institutes of Health (NIH) were recruited to participate in semi-structured interviews. The 2015 Supportive Care Needs model by Pelenstov, which defines critical needs in families with rare/undiagnosed diseases, provided a framework for interview guide development and transcript analysis (Pelentsov et al in Disabil Health J 8(4):475-491, 2015. https://doi.org/10.1016/J.DHJO.2015.03.009 ). A deductive, iterative coding approach was used to identify common unifying themes. Fourteen parents from 13 families were interviewed. The average child's age was 11 years (range 3-18) and an average 63% of their life had been spent searching for a diagnosis. Our analysis found that alignment or misalignment of parent and child needs impact the trajectory of the diagnostic search. When needs and desires align, reevaluation of a decision to pursue a diagnosis is limited. However, when there is conflict between parent and child desires, there is reevaluation, and often a pause, in the search. This tension is exacerbated when children are adolescents and attempting to balance their dependence on parents for medical care with a natural desire for independence. Our results provide novel insights into the roles of adolescents in the diagnostic odyssey. The tension between desired and realistic developmental outcomes for parents and adolescents impacts if, and how, the search for a diagnosis progresses.

Long-term Burosumab Administration Is Safe and Effective in Adults With X-linked Hypophosphatemia

CONTEXT

Burosumab was developed as a treatment option for patients with the rare, lifelong, chronically debilitating, genetic bone disease X-linked hypophosphatemia (XLH).

OBJECTIVE

Collect additional information on the safety, immunogenicity, and clinical response to long-term administration of burosumab.

METHODS

UX023-CL203 (NCT02312687) was a Phase 2b, open-label, single-arm, long-term extension study of adult subjects with XLH who participated in KRN23-INT-001 or KRN23-INT-002 studies. The long-term UX023-CL203 study (January 5, 2015 through November 30, 2018) provided data up to 184 weeks. Participants in UX023-CL203 received burosumab based on the last dose in the prior KRN23-INT-001 or KRN23-INT-002 studies (0.3, 0.6, or 1.0 mg/kg given by subcutaneous injection every 4 weeks). At Week 12, burosumab could be titrated upward/downward to achieve fasting serum phosphate levels within the normal range. Primary objectives included long-term safety, the proportion of subjects achieving fasting serum phosphate in the normal range, changes in bone turnover markers, patient-reported outcomes for pain and stiffness, and measures of mobility.

RESULTS

Fasting serum phosphate levels at the midpoint of the dosing interval (2 weeks postdose, the time of peak effect) were within the normal range in 85% to 100% of subjects. Measures of phosphate metabolism and bone biomarkers generally improved with burosumab therapy, approaching or reaching their respective normal ranges by study end. Improvements in patient-reported outcomes and mobility were sustained throughout the observation period. No new safety findings emerged with longer-term burosumab treatment.

CONCLUSION

These data support the conclusion that burosumab therapy may be a safe and effective long-term treatment option for adult patients with XLH.

Biallelic variants in KARS1 are associated with neurodevelopmental disorders and hearing loss recapitulated by the knockout zebrafish

PURPOSE

Pathogenic variants in Lysyl-tRNA synthetase 1 (KARS1) have increasingly been recognized as a cause of early-onset complex neurological phenotypes. To advance the timely diagnosis of KARS1-related disorders, we sought to delineate its phenotype and generate a disease model to understand its function in vivo.

METHODS

Through international collaboration, we identified 22 affected individuals from 16 unrelated families harboring biallelic likely pathogenic or pathogenic in KARS1 variants. Sequencing approaches ranged from disease-specific panels to genome sequencing. We generated loss-of-function alleles in zebrafish.

RESULTS

We identify ten new and four known biallelic missense variants in KARS1 presenting with a moderate-to-severe developmental delay, progressive neurological and neurosensory abnormalities, and variable white matter involvement. We describe novel KARS1-associated signs such as autism, hyperactive behavior, pontine hypoplasia, and cerebellar atrophy with prevalent vermian involvement. Loss of kars1 leads to upregulation of p53, tissue-specific apoptosis, and downregulation of neurodevelopmental related genes, recapitulating key tissue-specific disease phenotypes of patients. Inhibition of p53 rescued several defects of kars1^-/- knockouts.

CONCLUSION

Our work delineates the clinical spectrum associated with KARS1 defects and provides a novel animal model for KARS1-related human diseases revealing p53 signaling components as potential therapeutic targets.

Clinical effect and safety profile of pegzilarginase in patients with arginase 1 deficiency

Hyperargininemia in patients with arginase 1 deficiency (ARG1-D) is considered a key driver of disease manifestations, including spasticity, developmental delay, and seizures. Pegzilarginase (AEB1102) is an investigational enzyme therapy which is being developed as a novel arginine lowering approach. We report the safety and efficacy of intravenously (IV) administered pegzilarginase in pediatric and adult ARG1-D patients (n = 16) from a Phase 1/2 study (101A) and the first 12 weeks of an open-label extension study (102A). Substantial disease burden at baseline included lower-limb spasticity, developmental delay, and previous hyperammonemic episodes in 75%, 56%, and 44% of patients, respectively. Baseline plasma arginine (pArg) was elevated (median 389 μM, range 238-566) on standard disease management. Once weekly repeat dosing resulted in a median decrease of pArg of 277 μM after 20 cumulative doses (n = 14) with pArg in the normal range (40 to 115 μM) in 50% of patients at 168 hours post dose (mean pegzilarginase dose 0.10 mg/kg). Lowering pArg was accompanied by improvements in one or more key mobility assessments (6MWT, GMFM-D & E) in 79% of patients. In 101A, seven hypersensitivity reactions occurred in four patients (out of 162 infusions administered). Other common treatment-related adverse events (AEs) included vomiting, hyperammonemia, pruritus, and abdominal pain. Treatment-related serious AEs that occurred in five patients were all observed in 101A. Pegzilarginase was effective in lowering pArg levels with an accompanying clinical response in patients with ARG1-D. The improvements with pegzilarginase occurred in patients receiving standard treatment approaches, which suggests that pegzilarginase could offer benefit over existing disease management.

Clinical manifestations and management of fatty acid oxidation disorders

Fatty acid oxidation disorders (FAOD) are a group of rare, autosomal recessive, metabolic disorders caused by variants of the genes for the enzymes and proteins involved in the transport and metabolism of fatty acids in the mitochondria. Those affected by FAOD are unable to convert fatty acids into tricarboxylic acid cycle intermediates such as acetyl-coenzyme A, resulting in decreased adenosine triphosphate and glucose for use as energy in a variety of high-energy-requiring organ systems. Signs and symptoms may manifest in infants but often also appear in adolescents or adults during times of increased metabolic demand, such as fasting, physiologic stress, and prolonged exercise. Patients with FAOD present with a highly heterogeneous clinical spectrum. The most common clinical presentations include hypoketotic hypoglycemia, liver dysfunction, cardiomyopathy, rhabdomyolysis, and skeletal myopathy, as well as peripheral neuropathy and retinopathy in some subtypes. Despite efforts to detect FAOD through newborn screening and manage patients early, symptom onset can be sudden and serious, even resulting in death. Therefore, it is critical to identify quickly and accurately the key signs and symptoms of patients with FAOD to manage metabolic decompensations and prevent serious comorbidities.

Tutorial: Triheptanoin and Nutrition Management for Treatment of Long-Chain Fatty Acid Oxidation Disorders

BACKGROUND

Patients with severe long-chain fatty acid oxidation disorders (LC-FAODs) experience serious morbidity and mortality despite traditional dietary management including medium-chain triglyceride (MCT)-supplemented, low-fat diets. Triheptanoin is a triglyceride oil that is broken down to acetyl-coenzyme A (CoA) and propionyl-CoA, which replenishes deficient tricarboxylic acid cycle intermediates. We report the complex medical and nutrition management of triheptanoin therapy initiated emergently for 3 patients with LC-FAOD.

METHODS

Triheptanoin (Ultragenyx Pharmaceutical, Inc, Novato, CA, USA) was administered to 3 patients with LC-FAOD on a compassionate-use basis. Triheptanoin was mixed with non-MCT-containing low-fat formula. Patients were closely followed with regular cardiac and laboratory monitoring.

RESULTS

Cardiac ejection fraction normalized after triheptanoin initiation. Patients experienced fewer hospitalizations related to metabolic crises while on triheptanoin. Patient 1 has tolerated oral administration without difficulty since birth. Patients 2 and 3 experienced increased diarrhea. Recurrent breakdown of the silicone gastrostomy tube occurred in patient 3, whereas the polyurethane nasogastric tube for patient 2 remained intact. Patient 3 experiences recurrent episodes of elevated creatine kinase levels and muscle weakness associated with illness. Patient 3 had chronically elevated C10-acylcarnitines while on MCT supplementation, which normalized after initiation of triheptanoin and discontinuation of MCT oil.

CONCLUSIONS

Triheptanoin can ameliorate acute cardiomyopathy and increase survival in patients with severe LC-FAOD. Substituting triheptanoin for traditional MCT-based treatment improves clinical outcomes. MCT oil might be less effective in carnitine-acylcarnitine translocase deficiency patients compared with other FAODs and needs further investigation.

De novo EIF2AK1 and EIF2AK2 Variants Are Associated with Developmental Delay, Leukoencephalopathy, and Neurologic Decompensation

EIF2AK1 and EIF2AK2 encode members of the eukaryotic translation initiation factor 2 alpha kinase (EIF2AK) family that inhibits protein synthesis in response to physiologic stress conditions. EIF2AK2 is also involved in innate immune response and the regulation of signal transduction, apoptosis, cell proliferation, and differentiation. Despite these findings, human disorders associated with deleterious variants in EIF2AK1 and EIF2AK2 have not been reported. Here, we describe the identification of nine unrelated individuals with heterozygous de novo missense variants in EIF2AK1 (1/9) or EIF2AK2 (8/9). Features seen in these nine individuals include white matter alterations (9/9), developmental delay (9/9), impaired language (9/9), cognitive impairment (8/9), ataxia (6/9), dysarthria in probands with verbal ability (6/9), hypotonia (7/9), hypertonia (6/9), and involuntary movements (3/9). Individuals with EIF2AK2 variants also exhibit neurological regression in the setting of febrile illness or infection. We use mammalian cell lines and proband-derived fibroblasts to further confirm the pathogenicity of variants in these genes and found reduced kinase activity. EIF2AKs phosphorylate eukaryotic translation initiation factor 2 subunit 1 (EIF2S1, also known as EIF2α), which then inhibits EIF2B activity. Deleterious variants in genes encoding EIF2B proteins cause childhood ataxia with central nervous system hypomyelination/vanishing white matter (CACH/VWM), a leukodystrophy characterized by neurologic regression in the setting of febrile illness and other stressors. Our findings indicate that EIF2AK2 missense variants cause a neurodevelopmental syndrome that may share phenotypic and pathogenic mechanisms with CACH/VWM.

Long-term safety and efficacy of glycerol phenylbutyrate for the management of urea cycle disorder patients

INTRODUCTION

Glycerol phenylbutyrate (GPB) is currently approved for use in the US and Europe for patients of all ages with urea cycle disorders (UCD) who cannot be managed with protein restriction and/or amino acid supplementation alone. Currently available data on GPB is limited to 12 months exposure. Here, we present long-term experience with GPB.

METHODS

This was an open-label, long-term safety study of GPB conducted in the US (17 sites) and Canada (1 site) monitoring the use of GPB in UCD patients who had previously completed 12 months of treatment in the previous safety extension studies. Ninety patients completed the previous studies with 88 of these continuing into the long-term evaluation. The duration of therapy was open ended until GPB was commercially available. The primary endpoint was the rate of adverse events (AEs). Secondary endpoints were venous ammonia levels, number and causes of hyperammonemic crises (HACs) and neuropsychological testing.

RESULTS

A total of 45 pediatric patients between the ages of 1 to 17 years (median 7 years) and 43 adult patients between the ages of 19 and 61 years (median 30 years) were enrolled. The treatment emergent adverse events (TEAE) reported in ≥10% of adult or pediatric patients were consistent with the TEAEs reported in the previous safety extension studies with no increase in the overall incidence of TEAEs and no new TEAEs that indicated a new safety signal. Mean ammonia levels remained stable and below the adult upper limit of normal (<35 µmol/L) through 24 months of treatment in both the pediatric and adult population. Over time, glutamine levels decreased in the overall population. The mean annualized rate of HACs (0.29) established in the previously reported 12-month follow-up study was maintained with continued GPB exposure.

CONCLUSION

Following the completion of 12-month follow-up studies with GPB treatment, UCD patients were followed for an additional median of 1.85 (range 0 to 5.86) years in the present study with continued maintenance of ammonia control, similar rates of adverse events, and no new adverse events identified.

A Framework for Evaluation of the Higher-Risk Infant After a Brief Resolved Unexplained Event

In 2016, the American Academy of Pediatrics published a clinical practice guideline that more specifically defined apparent life-threatening events as brief resolved unexplained events (BRUEs) and provided evidence-based recommendations for the evaluation of infants who meet lower-risk criteria for a subsequent event or serious underlying disorder. The clinical practice guideline did not provide recommendations for infants meeting higher-risk criteria, an important and common population of patients. Therefore, we propose a tiered approach for clinical evaluation and management of higher-risk infants who have experienced a BRUE. Because of a vast array of potential causes, the initial evaluation prioritizes the diagnosis of time-sensitive conditions for which delayed diagnosis or treatment could impact outcomes, such as child maltreatment, feeding problems, cardiac arrhythmias, infections, and congenital abnormalities. The secondary evaluation addresses problems that are less sensitive to delayed diagnosis or treatment, such as dysphagia, intermittent partial airway obstruction, and epilepsy. The authors recommend a tailored, family-centered, multidisciplinary approach to evaluation and management of all higher-risk infants with a BRUE, whether accomplished during hospital admission or through coordinated outpatient care. The proposed framework was developed by using available evidence and expert consensus.

Expanding clinical phenotype in CACNA1C related disorders: From neonatal onset severe epileptic encephalopathy to late-onset epilepsy

CACNA1C (NM_000719.6) encodes an L-type calcium voltage-gated calcium channel (Ca_v 1.2), and pathogenic variants have been associated with two distinct clinical entities: Timothy syndrome and Brugada syndrome. Thus far, CACNA1C has not been reported as a gene associated with epileptic encephalopathy and is less commonly associated with epilepsy. We report three individuals from two families with variants in CACNA1C. Patient 1 presented with neonatal onset epileptic encephalopathy (NOEE) and was found to have a de novo missense variant in CACNA1C (c.4087G>A (p.V1363M)) on exome sequencing. In Family 2, Patient 2 presented with congenital cardiac anomalies and cardiomyopathy and was found to have a paternally inherited splice site variant, c.3717+1_3717+2insA, on a cardiomyopathy panel. Her father, Patient 3, presented with learning difficulties, late-onset epilepsy, and congenital cardiac anomalies. Family 2 highlights variable expressivity seen within a family. This case series expands the clinical and molecular phenotype of CACNA1C-related disorders and highlights the need to include CACNA1C on epilepsy gene panels.

Fatty acid oxidation disorders

Fatty acid oxidation disorders (FAODs) are inborn errors of metabolism due to disruption of either mitochondrial β-oxidation or the fatty acid transport using the carnitine transport pathway. The presentation of a FAOD will depend upon the specific disorder, but common elements may be seen, and ultimately require a similar treatment. Initial presentations of the FAODs in the neonatal period with severe symptoms include cardiomyopathy, while during infancy and childhood liver dysfunction and hypoketotic hypoglycemia are common. Episodic rhabdomyolysis is frequently the initial presentation during or after adolescence; although, these symptoms may develop at any age for most of the FAODs The treatment of all FAOD's include avoidance of fasting, aggressive treatment during illness, and supplementation of carnitine, if necessary. The long-chain FAODs differ by requiring a fat-restricted diet and supplementation of medium chain triglyceride oil and often docosahexaenoic acid (DHA)-an essential fatty acid, crucial for brain, visual, and immune functions and prevention of fat soluble vitamin deficiencies. The FAOD are a group of autosomal recessive disorders associated with significant morbidity and mortality, but early diagnosis on newborn screening (NBS) and early initiation of treatment are improving outcomes. There is a need for clinical studies including randomized, controlled, therapeutic trials to continue to evaluate current understanding and to implement future therapies.

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.

Newborn screening for proximal urea cycle disorders: Current evidence supporting recommendations for newborn screening

Current newborn screening (NBS) for urea cycle disorders (UCD) is incomplete as only distal UCDs are included in most NBS programs by measuring elevated amino acid concentrations. NBS for the proximal UCDs involves the detection in NBS spots of low citrulline values, a finding which is often overlooked because it is considered to be inadequate. We retrospectively analyzed NBS blood spots from known UCD patients comparing the utility of the Region 4 Stork (R4S) interpretive tools to conventional cutoff based interpretation. This study shows the utility of R4S tools in detecting all UCDs, and provides evidence to support the nomination to add proximal UCDs to the recommended uniform screening panel.

Defining the phenotypic spectrum of SLC6A1 mutations

OBJECTIVE

Pathogenic SLC6A1 variants were recently described in patients with myoclonic atonic epilepsy (MAE) and intellectual disability (ID). We set out to define the phenotypic spectrum in a larger cohort of SCL6A1-mutated patients.

METHODS

We collected 24 SLC6A1 probands and 6 affected family members. Four previously published cases were included for further electroclinical description. In total, we reviewed the electroclinical data of 34 subjects.

RESULTS

Cognitive development was impaired in 33/34 (97%) subjects; 28/34 had mild to moderate ID, with language impairment being the most common feature. Epilepsy was diagnosed in 31/34 cases with mean onset at 3.7 years. Cognitive assessment before epilepsy onset was available in 24/31 subjects and was normal in 25% (6/24), and consistent with mild ID in 46% (11/24) or moderate ID in 17% (4/24). Two patients had speech delay only, and 1 had severe ID. After epilepsy onset, cognition deteriorated in 46% (11/24) of cases. The most common seizure types were absence, myoclonic, and atonic seizures. Sixteen cases fulfilled the diagnostic criteria for MAE. Seven further patients had different forms of generalized epilepsy and 2 had focal epilepsy. Twenty of 31 patients became seizure-free, with valproic acid being the most effective drug. There was no clear-cut correlation between seizure control and cognitive outcome. Electroencephalography (EEG) findings were available in 27/31 patients showing irregular bursts of diffuse 2.5-3.5 Hz spikes/polyspikes-and-slow waves in 25/31. Two patients developed an EEG pattern resembling electrical status epilepticus during sleep. Ataxia was observed in 7/34 cases. We describe 7 truncating and 18 missense variants, including 4 recurrent variants (Gly232Val, Ala288Val, Val342Met, and Gly362Arg).

SIGNIFICANCE

Most patients carrying pathogenic SLC6A1 variants have an MAE phenotype with language delay and mild/moderate ID before epilepsy onset. However, ID alone or associated with focal epilepsy can also be observed.

Brief Resolved Unexplained Events (Formerly Apparent Life-Threatening Events) and Evaluation of Lower-Risk Infants

This is the first clinical practice guideline from the American Academy of Pediatrics that specifically applies to patients who have experienced an apparent life-threatening event (ALTE). This clinical practice guideline has 3 objectives. First, it recommends the replacement of the term ALTE with a new term, brief resolved unexplained event (BRUE). Second, it provides an approach to patient evaluation that is based on the risk that the infant will have a repeat event or has a serious underlying disorder. Finally, it provides management recommendations, or key action statements, for lower-risk infants. The term BRUE is defined as an event occurring in an infant younger than 1 year when the observer reports a sudden, brief, and now resolved episode of ≥1 of the following: (1) cyanosis or pallor; (2) absent, decreased, or irregular breathing; (3) marked change in tone (hyper- or hypotonia); and (4) altered level of responsiveness. A BRUE is diagnosed only when there is no explanation for a qualifying event after conducting an appropriate history and physical examination. By using this definition and framework, infants younger than 1 year who present with a BRUE are categorized either as (1) a lower-risk patient on the basis of history and physical examination for whom evidence-based recommendations for evaluation and management are offered or (2) a higher-risk patient whose history and physical examination suggest the need for further investigation and treatment but for whom recommendations are not offered. This clinical practice guideline is intended to foster a patient- and family-centered approach to care, reduce unnecessary and costly medical interventions, improve patient outcomes, support implementation, and provide direction for future research. Each key action statement indicates a level of evidence, the benefit-harm relationship, and the strength of recommendation.

Self-reported treatment-associated symptoms among patients with urea cycle disorders participating in glycerol phenylbutyrate clinical trials

BACKGROUND

Health care outcomes have been increasingly assessed through health-related quality of life (HRQoL) measures. While the introduction of nitrogen-scavenging medications has improved survival in patients with urea cycle disorders (UCDs), they are often associated with side effects that may affect patient compliance and outcomes.

METHODS

Symptoms commonly associated with nitrogen-scavenging medications were evaluated in 100 adult and pediatric participants using a non-validated UCD-specific questionnaire. Patients or their caregivers responded to a pre-defined list of symptoms known to be associated with the use of these medications. Responses were collected at baseline (while patients were receiving sodium phenylbutyrate [NaPBA]) and during treatment with glycerol phenylbutyrate (GPB).

RESULTS

After 3 months of GPB dosing, there were significant reductions in the proportion of patients with treatment-associated symptoms (69% vs. 46%; p<0.0001), the number of symptoms per patient (2.5 vs. 1.1; p<0.0001), and frequency of the more commonly reported individual symptoms such as body odor, abdominal pain, nausea, burning sensation in mouth, vomiting, and heartburn (p<0.05). The reduction in symptoms was observed in both pediatric and adult patients. The presence or absence of symptoms or change in severity did not correlate with plasma ammonia levels or NaPBA dose.

CONCLUSIONS

The reduction in symptoms following 3 months of open-label GPB dosing was similar in pediatric and adult patients and may be related to chemical structure and intrinsic characteristics of the product rather than its effect on ammonia control.

Ethical considerations of population screening for late-onset genetic disease

Population-based genetic screening has been a mainstay of public health in the United States for many years. The goal of genetic screening is to identify individuals at increased risk for treatable diseases. The evolution of genetic testing to include multi-disease panels allows for new screening applications which challenge the traditional model of clinical genetics care by the identification of late-onset disorders in an asymptomatic fetus, child, or adult. We present two unique examples of individuals referred to a biochemical genetics clinic due to the detection of late-onset Pompe disease by population-based screening modalities. We review early experiences in counseling and management of pre-symptomatic individuals and highlight some of the primary ethical factors warranting consideration as we enter the era of genomic medicine.

Blood ammonia and glutamine as predictors of hyperammonemic crises in patients with urea cycle disorder

Purpose

To examine predictors of ammonia exposure and hyperammonemic crises (HAC) in patients with urea cycle disorders (UCDs).

Methods

The relationships between fasting ammonia, daily ammonia exposure, and HACs were analyzed in >100 UCD patients.

Results

Fasting ammonia correlated strongly with daily ammonia exposure (r=0.764, p<0.001). For patients with fasting ammonia levels <0.5 ULN, 0.5 to <1.0 ULN, and ≥1.0 ULN, the probability of a normal average daily ammonia value was 87%, 60%, and 39%, respectively, and 10.3%, 14.1%, and 37.0% of these patients experienced ≥1 HAC over 12 months. Time to first HAC was shorter (p=0.008) and relative risk (4.5×; p=0.011) and rate (~5×, p=0.006) of HACs higher in patients with fasting ammonia ≥1.0 ULN vs. <0.5ULN; relative risk was even greater (20×; p=0.009) in patients ≥6 years. A 10 or 25 μmol/L increase in ammonia exposure increased the relative risk of a HAC by 50% and >200% (p<0.0001), respectively. The relationship between ammonia and HAC risk appeared independent of treatment, age, UCD subtype, dietary protein intake, or blood urea nitrogen. Fasting glutamine correlated weakly with AUC_0-24 and was not a significant predictor of HACs.

Conclusions

Fasting ammonia correlates strongly and positively with daily ammonia exposure and with the risk and rate of HACs, suggesting that UCD patients may benefit from tight ammonia control.

Infants suspected to have very-long chain acyl-CoA dehydrogenase deficiency from newborn screening

Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is a fatty acid oxidation disorder with widely varying presentations that has presented a significant challenge to newborn screening (NBS). The Western States Regional Genetics Services Collaborative developed a workgroup to study infants with NBS positive for VLCADD. We performed retrospective analysis of newborns with elevated C14:1-acylcarnitine on NBS in California, Oregon, Washington, and Hawai'i including available confirmatory testing and clinical information. Overall, from 2,802,504 children screened, there were 242 cases screen-positive for VLCADD. There were 34 symptomatic true positive cases, 18 asymptomatic true positives, 112 false positives, 55 heterozygotes, 11 lost to follow-up, and 12 other disorders. One in 11,581 newborns had an abnormal NBS for suspected VLCADD. Comparison of analytes and analyte ratios from the NBS demonstrated statistically significant differences between true positive and false positive groups for C14:1, C14, C14:1/C2, and C14:1/C16. The positive predictive value for all true positive cases was 94%, 54%, and 23% when C14:1 was ≥2.0 μM, ≥1.0 μM, and ≥0.7 μM, respectively. Sequential post-analytical analysis could reduce the referral rate in 25.8% of cases. This study is the largest reported follow-up of infants with NBS screen-positive results for suspected VLCADD and demonstrates the necessity of developing comprehensive and consistent long-term follow-up NBS systems. Application of clinical information revealed differences between symptomatic and asymptomatic children with VLCADD. Comparison of NBS analytes and analyte ratios may be valuable in developing more effective diagnostic algorithms.

Asymptomatic methylmalonic acidemia in a homozygous MUT mutation (p.P86L)

Deficiency in methylmalonyl-coenzyme A mutase (MCM) is associated with accumulation of methylmalonic acid (MMA) and clinical outcomes that include early death and neurological impairment. Reported here are two unrelated patients with a homozygous p.P86L mutation in the MUT gene, which encodes MCM, diagnosed following newborn screening. This is the first description of a homozygous mutation in the N-terminal extended segment of the MCM apoenzyme. Both in vitro and in vivo testing did not find a response to supplemental hydroxocobalamin. After discontinuation of hydroxocobalamin in one patient, serum MMA level remained elevated but stable, while urine MMA increased. Both patients have remained asymptomatic with normal development. The observed homozygous p.P86L mutation in the N-terminal extended segment may yield reduced MCM activity and is refractory to hydroxocobalamin supplementation, while not inducing a metabolically unstable phenotype. These genotype-phenotype associations further enhance the understanding of methylmalonic acidemia, which will continue to improve patient care.

Ammonia control and neurocognitive outcome among urea cycle disorder patients treated with glycerol phenylbutyrate

Glycerol phenylbutyrate is under development for treatment of urea cycle disorders (UCDs), rare inherited metabolic disorders manifested by hyperammonemia and neurological impairment. We report the results of a pivotal Phase 3, randomized, double-blind, crossover trial comparing ammonia control, assessed as 24-hour area under the curve (NH3 -AUC0-24hr ), and pharmacokinetics during treatment with glycerol phenylbutyrate versus sodium phenylbutyrate (NaPBA) in adult UCD patients and the combined results of four studies involving short- and long-term glycerol phenylbutyrate treatment of UCD patients ages 6 and above. Glycerol phenylbutyrate was noninferior to NaPBA with respect to ammonia control in the pivotal study, with mean (standard deviation, SD) NH3 -AUC0-24hr of 866 (661) versus 977 (865) μmol·h/L for glycerol phenylbutyrate and NaPBA, respectively. Among 65 adult and pediatric patients completing three similarly designed short-term comparisons of glycerol phenylbutyrate versus NaPBA, NH3 -AUC0-24hr was directionally lower on glycerol phenylbutyrate in each study, similar among all subgroups, and significantly lower (P < 0.05) in the pooled analysis, as was plasma glutamine. The 24-hour ammonia profiles were consistent with the slow-release behavior of glycerol phenylbutyrate and better overnight ammonia control. During 12 months of open-label glycerol phenylbutyrate treatment, average ammonia was normal in adult and pediatric patients and executive function among pediatric patients, including behavioral regulation, goal setting, planning, and self-monitoring, was significantly improved.

CONCLUSION

Glycerol phenylbutyrate exhibits favorable pharmacokinetics and ammonia control relative to NaPBA in UCD patients, and long-term glycerol phenylbutyrate treatment in pediatric UCD patients was associated with improved executive function (ClinicalTrials.gov NCT00551200, NCT00947544, NCT00992459, NCT00947297). (HEPATOLOGY 2012).

Urinary phenylacetylglutamine as dosing biomarker for patients with urea cycle disorders

We have analyzed pharmacokinetic data for glycerol phenylbutyrate (also GT4P or HPN-100) and sodium phenylbutyrate with respect to possible dosing biomarkers in patients with urea cycle disorders (UCD).

STUDY DESIGN

These analyses are based on over 3000 urine and plasma data points from 54 adult and 11 pediatric UCD patients (ages 6-17) who participated in three clinical studies comparing ammonia control and pharmacokinetics during steady state treatment with glycerol phenylbutyrate or sodium phenylbutyrate. All patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate or sodium phenylbutyrate in a cross over fashion and underwent 24-hour blood samples and urine sampling for phenylbutyric acid, phenylacetic acid and phenylacetylglutamine.

RESULTS

Patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate ranging from 1.5 to 31.8 g/day and of sodium phenylbutyrate ranging from 1.3 to 31.7 g/day. Plasma metabolite levels varied widely, with average fluctuation indices ranging from 1979% to 5690% for phenylbutyric acid, 843% to 3931% for phenylacetic acid, and 881% to 1434% for phenylacetylglutamine. Mean percent recovery of phenylbutyric acid as urinary phenylacetylglutamine was 66.4 and 69.0 for pediatric patients and 68.7 and 71.4 for adult patients on glycerol phenylbutyrate and sodium phenylbutyrate, respectively. The correlation with dose was strongest for urinary phenylacetylglutamine excretion, either as morning spot urine (r = 0.730, p < 0.001) or as total 24-hour excretion (r = 0.791 p<0.001), followed by plasma phenylacetylglutamine AUC(24-hour), plasma phenylacetic acid AUC(24-hour) and phenylbutyric acid AUC(24-hour). Plasma phenylacetic acid levels in adult and pediatric patients did not show a consistent relationship with either urinary phenylacetylglutamine or ammonia control.

CONCLUSION

The findings are collectively consistent with substantial yet variable pre-systemic (1st pass) conversion of phenylbutyric acid to phenylacetic acid and/or phenylacetylglutamine. The variability of blood metabolite levels during the day, their weaker correlation with dose, the need for multiple blood samples to capture trough and peak, and the inconsistency between phenylacetic acid and urinary phenylacetylglutamine as a marker of waste nitrogen scavenging limit the utility of plasma levels for therapeutic monitoring. By contrast, 24-hour urinary phenylacetylglutamine and morning spot urine phenylacetylglutamine correlate strongly with dose and appear to be clinically useful non-invasive biomarkers for compliance and therapeutic monitoring.

Next-generation sequencing for mitochondrial diseases: a wide diagnostic spectrum

BACKGROUND

The current diagnostic approach for mitochondrial disorders requires invasive procedures such as muscle biopsy and multiple biochemical testing but the results are often inconclusive. Clinical sequencing tests are available only for a limited number of genes. Recently, massively parallel sequencing has become a powerful tool for testing genetically heterogeneous conditions such as mitochondrial disorders.

METHODS

Targeted next-generation sequencing was performed on 26 patients with known or suspected mitochondrial disorders using in-solution capture for the exons of 908 known and candidate nuclear genes and an Illumina genome analyzer.

RESULTS

None of the 18 patients with various abnormal respiratory chain complex (RCC) activities had molecular defects in either subunits or assembly factors of mitochondrial RCC enzymes except a reference control sample with known mutations in SURF1. Instead, several variants in known pathogenic genes including CPT2, POLG, PDSS1, UBE3A, SDHD, and a few potentially pathogenic variants in candidate genes such as MTO1 or SCL7A13 were identified.

CONCLUSIONS

Sequencing only nuclear genes for RCC subunits and assembly factors may not provide the diagnostic answers for suspected patients with mitochondrial disorders. The present findings indicate that the diagnostic spectrum of mitochondrial disorders is much broader than previously thought, which could potentially lead to misdiagnosis and/or inappropriate treatment. Overall analytic sensitivity and precision appear acceptable for clinical testing. Despite the limitations in finding mutations in all patients, the present findings underscore the considerable clinical benefits of targeted next-generation sequencing and serve as a prototype for extending the clinical evaluation in this clinically heterogeneous patient group.

Ammonia control in children with urea cycle disorders (UCDs); phase 2 comparison of sodium phenylbutyrate and glycerol phenylbutyrate

Twenty four hour ammonia profiles and correlates of drug effect were examined in a phase 2 comparison of sodium phenylbutyrate (NaPBA) and glycerol phenylbutyrate (GPB or HPN-100), an investigational drug being developed for urea cycle disorders (UCDs).

STUDY DESIGN

Protocol HPN-100-005 involved open label fixed-sequence switch-over from the prescribed NaPBA dose to a PBA-equimolar GPB dose with controlled diet. After 7 days on NaPBA or GPB, subjects underwent 24-hour blood sampling for ammonia and drug metabolite levels as well as measurement of 24-hour urinary phenyacetylglutamine (PAGN). Adverse events (AEs), safety labs and triplicate ECGs were monitored.

RESULTS

Eleven subjects (9 OTC, 1 ASS, 1 ASL) enrolled and completed the switch-over from NaPBA (mean dose=12.4 g/d or 322 mg/kg/d; range=198-476 mg/kg/d) to GPB (mean dose=10.8 mL or 0.284 mL/kg/d or 313 mg/kg/d; range=192-449 mg/kg/d). Possibly-related AEs were reported in 2 subjects on NaPBA and 4 subjects on GPB. All were mild, except for one moderate AE of vomiting on GPB related to an intercurrent illness. No clinically significant laboratory or ECG changes were observed. Ammonia was lowest after overnight fast, peaked postprandially in the afternoon to early evening and varied widely over 24h with occasional values >100 μmol/L without symptoms. Ammonia values were ~25% lower on GPB vs. NaPBA (p≥0.1 for ITT and p<0.05 for per protocol population). The upper 95% confidence interval for the difference between ammonia on GPB vs. NaPBA in the ITT population (95% CI 0.575, 1.061; p=0.102) was less than the predefined non-inferiority margin of 1.25 and less than 1.0 in the pre-defined per-protocol population (95% CI 0.516, 0.958; p<0.05). No statistically significant differences were observed in plasma phenylacetic acid and PAGN exposure during dosing with GPB vs. NaPBA, and the percentage of orally administered PBA excreted as PAGN (66% for GPB vs. 69% for NaPBA) was very similar. GPB and NaPBA dose correlated best with urinary-PAGN.

CONCLUSIONS

These findings suggest that GPB is at least equivalent to NaPBA in terms of ammonia control, has potential utility in pediatric UCD patients and that U-PAGN is a clinically useful biomarker for dose selection and monitoring.

Establishing a consortium for the study of rare diseases: The Urea Cycle Disorders Consortium

The Urea Cycle Disorders Consortium (UCDC) was created as part of a larger network established by the National Institutes of Health to study rare diseases. This paper reviews the UCDC's accomplishments over the first 6years, including how the Consortium was developed and organized, clinical research studies initiated, and the importance of creating partnerships with patient advocacy groups, philanthropic foundations and biotech and pharmaceutical companies.

A cognitively normal PDH-deficient 18-year-old man carrying the R263G mutation in the PDHA1 gene

Pyruvate dehydrogenase (PDH) is a crucial multienzyme system linking glycolysis to the tricarboxylic acid cycle by catalysing the decarboxylation of pyruvate to acetyl-CoA. Deficiency in pyruvate dehydrogenase is most commonly secondary to mutations in the X-linked PDHA1 gene encoding the E1 alpha subunit. There is a wide range of clinical presentations from severe neonatal lactic acidosis to chronic encephalopathy (Leigh syndrome). In recent years, a small subset of patients was recognized with less severe involvement, presenting initially only with intermittent symptoms, mainly of ataxia. Most of these patients remain stable for a number of years before developing progressive neurological deterioration around puberty at the latest. There does not appear to be a reliable correlation between genotype, phenotype, or enzyme activity. This makes counselling in a clinical setting challenging. We report a case with a previously known common mutation in PDHA1 (R263G) with an excellent outcome at 18 years of age. Previous patients with this mutation have presented with mental retardation and/or Leigh syndrome, while our patient's clinical outcome is exceptional. He is cognitively normal and has normal brain MRI. His management includes a stringent carbohydrate-free diet, as well as supplementation with thiamine, carnitine and vitamin E. This case further broadens the clinical spectrum, including now an example of a cognitively normal adult with PDH deficiency.

Biochemical correction of very long-chain acyl-CoA dehydrogenase deficiency following adeno-associated virus gene therapy

We report the development of a gene replacement strategy for very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. VLCAD is a mitochondrial enzyme involved in fatty acid beta-oxidation, a key step in energy production during times of fasting or stress. Deficiency of VLCAD classically presents as hepatic dysfunction, hypoglycemia, cardiomyopathy, rhabdomyolysis, and/or sudden death. While dietary therapy for VLCAD deficiency has proven beneficial in preventing some symptoms, a risk of metabolic catastrophic decompensation remains throughout life during times of increased energy demand. We designed a recombinant adeno-associated virus (AAV) expressing the human VLCAD gene (AAV8-hVLCAD). To demonstrate its in vivo activity, AAV8-hVLCAD was administered via the tail vein to VLCAD-knockout mice. A reduction in accumulated serum long-chain acylcarnitines and increased fasting tolerance judged on blood glucose concentrations were observed as of 11 days postinjections through >100 days. Western analysis of liver, skeletal muscle, and heart extracts using PEP1 anti-hVLCAD antibody revealed short-term hVLCAD expression in the liver and muscle and longer-term expression in heart. This demonstrates the ability of human VLCAD to correct the biochemical phenotype of VLCAD-deficient mice.

Ornithine transcarbamylase deficiency presenting as encephalopathy during adulthood following bariatric surgery

BACKGROUND

Neurological complications following bariatric surgery are rare. Whereas nutritional deficiencies are the most common cause of neurological symptoms, the unmasking of previously subclinical metabolic disorders can also lead to significant morbidity.

OBJECTIVE

To characterize the clinical presentation, serum biochemical fluctuations, and functional enzymatic analysis of a case of functional ornithine transcarbamylase deficiency unmasked by a dietary change following bariatric surgery.

DESIGN

Case report.

SETTING

Tertiary referral center, hospital (inpatient) setting.

PATIENT

A 29-year-old woman who presented with intermittent encephalopathy associated with recurrent hyperammonemia.

INTERVENTIONS

Clinical, biochemical, and mutational studies.

RESULTS

The pattern of intermittent hyperammonemia and encephalopathy following oral and parenteral nutrition suggested a urea cycle abnormality. Functional enzymatic assay results showed markedly reduced ornithine transcarbamylase activity in the absence of known coding mutations.

CONCLUSION

Previously asymptomatic ornithine transcarbamylase deficiency should be suspected in adult patients who develop recurrent hyperammonemia and encephalopathy following bariatric surgery.

Extensive acrochordons and pancreatic islet-cell tumors in tuberous sclerosis associated with TSC2 mutations

Acrochordons are frequently encountered benign skin lesions that may occasionally represent underlying pathology. Pancreatic islet-cell tumors are rare neoplasms and few cases have been described in patients with tuberous sclerosis complex (TSC). A 39-year-old man presenting in acute renal failure was referred to us for further diagnostic evaluation of coincidentally noted dysmorphic features. Physical examination revealed over 1,000 acrochordons in addition to findings meeting criteria for TSC. The diagnosis was confirmed by disclosure of mutation in the TSC2 gene. Further evaluation revealed pancreatic islet cell tumors. Acrochordons are a common skin lesion, but when presenting in an atypical manner or unusual number may be a sign of TSC and underlying occult pathology thereby warranting evaluation of TSC2. Additionally, mutations in TSC2 gene may be a risk factor for developing pancreatic islet-cell tumors.

Delineation of the cryptic 1qter deletion phenotype

The 1qter microdeletion is often reported in the literature as a part of a complex chromosome rearrangement. We describe a patient with a normal initial cytogenetic analysis later found by subtelomeric FISH to have a de novo isolated 1qter microdeletion. Further characterization was completed through microarray comparative genomic hybridization (CGH) and specific bacterial artificial chromosomes (BACs) to a region of 5.2-5.3 Mbp. Six additional cases were reviewed from a literature search. While no particular feature is specifically unique, the most frequently associated features include short stature, developmental delay and mental retardation, microcephaly, seizures, abnormal corpus callosum, and abnormal ear shape. This further delineates the phenotype and further narrows the chromosomal region responsible for a 1qter microdeletion phenotype.

In vitro characterization and in vivo expression of human very-long chain acyl-CoA dehydrogenase

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is a disorder of fatty acid beta-oxidation that can present at any age with cardiomyopathy, rhabdomyolysis, hepatic dysfunction, and/or nonketotic hypoglycemia. Through the expansion of newborn screening programs an increasing number of individuals with VLCAD deficiency are being identified prior to the onset of symptoms allowing early initiation of therapy. The development of a safe, durable, and effective VLCAD gene delivery system for use at the time of diagnosis could result in a significant improvement in the quality and duration of life for patients with VLCAD deficiency. To this end, we developed a construct containing the human VLCAD cDNA under the control of the strong CMV promoter (pCMV-hVLCAD). A novel rabbit polyclonal anti-VLCAD antibody was prepared using a 24 amino-acid peptide unique to the human VLCAD protein to study human VLCAD expression in immune competent mice. Antibody specificity was demonstrated in Western blots of human VLCAD deficient fibroblasts and in pCMV-hVLCAD transiently transfected VLCAD deficient fibroblasts. Transfected fibroblasts showed correction of the metabolic block as demonstrated by normalization of C14- and C16-acylcarnitine species in cell culture media and restoration of VLCAD activity in cells. Following tail vein injection of pCMV-hVLCAD into mice, we demonstrated expression of hVLCAD in liver. Altogether, these steps are important in the development of a durable gene therapy for VLCAD deficiency.

Mycoplasma testudineum sp. nov., from a desert tortoise (Gopherus agassizii) with upper respiratory tract disease

Mycoplasma testudineum sp. nov., first cultured from the upper respiratory tract of a clinically ill tortoise (Gopherus agassizii) in the Mohave Desert, was distinguished from previously described mollicutes serologically and by 16S rRNA gene sequence comparisons. It lacks a cell wall; ferments glucose, mannose, lactose and sucrose; does not produce ‘film and spots’; does not hydrolyse arginine, aesculin or urea; is sensitive to digitonin; and lacks phosphatase activity. The organism causes chronic rhinitis and conjunctivitis of tortoises. The type strain of M. testudineum is BH29T (=ATCC 700618T=MCCM 03231T).

Expression of cholera toxin B subunit oligomers in transgenic potato plants

A gene encoding the cholera toxin B subunit protein (CTB), fused to an endoplasmic reticulum (ER) retention signal (SEKDEL) was inserted adjacent to the bi-directional mannopine synthase P2 promoter in a plant expression vector containing a bacterial luciferase AB fusion gene (luxF) linked to the P1 promoter. Potato leaf explants were transformed by Agrobacterium tumefaciens carrying the vector and kanamycin-resistant plants were regenerated. The CTB-SEKDEL fusion gene was identified in the genomic DNA of bioluminescent plants by polymerase chain reaction amplification. Immunoblot analysis indicated that plant-derived CTB protein was antigenically indistinguishable from bacterial CTB protein, and that oligomeric CTB molecules (M(r) approximately 50 kDa) were the dominant molecular species isolated from transgenic potato leaf and tuber tissues. Similar to bacterial CTB, plant-synthesized CTB dissociated into monomers (M(r) approximately 15 kDa) during heat or acid treatment. The maximum amount of CTB protein detected in auxin-induced transgenic potato leaf and tuber tissues was approximately 0.3% of total soluble plant protein. Enzyme-linked immunosorbent assay methods indicated that plant-synthesized CTB protein bound specifically to GM1-ganglioside, the natural membrane receptor of cholera toxin. In the presence of the SEKDEL signal, CTB protein accumulates in potato tissues and is assembled into an oligomeric form that retains native biochemical and immunological properties. The expression of oligomeric CTB protein with immunological and biochemical properties identical to native CTB protein in edible plants opens the way for preparation of inexpensive food plant-based oral vaccines for protection against cholera and other pathogens in endemic areas throughout the world.

Don't forget the serratus

Patients quadriplegic at the C6 level may not be considered candidates for independent transfers and weight shifting because of lack of primary shoulder depressors. However, we have observed that some quadriplegics have been able to use the serratus anterior for this latissimus dorsi function. We present an example of this technique, demonstrated by a patient with a complete C6 injury, and compare him with a subject with normal musculature.

Incidence of lumbar disc surgery. A population-based study in Olmsted County, Minnesota, 1950-1979

Age- and sex-specific incidence rates of operation for suspected lumbar disc prolapse were determined for residents of Olmsted County, Minnesota, for the 30-year period 1950 through 1979. The incidence rate (adjusted to the age and sex distribution of the United States white population in 1980) was 52.3 per 100,000 person-years for all such operations and 46.3 per 100,000 person-years for initial operations. These rates remained fairly constant over the study period. A distinction was made between surgically proven and unproven cases of lumbar disc prolapse. Patients with a surgically proven lumbar disc prolapse had about 10 times the risk of another operation for disc prolapse within 10 years after the first operation compared with the general population.

Advances in orthotics for the patient with rheumatoid arthritis

Orthotics are externally applied devices which support a joint or enhance its function. In arthritis orthotics are prescribed to stabilize joints, provide better positioning, reduce pain, prevent deformity and improve function. Splints are used primarily for the upper extremity. Specially designed shoes can control foot and ankle pain and instability. Continuous passive motion devices are becoming widely used for early postoperative rehabilitation after arthroplasty. Unfortunately, few controlled studies have been performed to determine the utility of orthoses in patients with arthritis. Some of the most important questions on this subject are posed and available data discussed as well as the need for additional information.

Renal function in spinal cord injury: a preliminary report

To investigate the effect of current bladder management techniques on renal function in spinal cord injury (SCI), we followed 99 patients by frequent examinations, excretory urograms, and iothalamate short renal clearances. Fifty-eight percent of the subjects emptied their bladders by catheter-free methods (bladder retrained), 32% by intermittent self-catheterization, and 10% by indwelling urethral catheters. All remained clinically well, but more and earlier excretory urogram abnormalities occurred in the intermittent self-catheterization group. Twenty-one percent of the intermittent self-catheterization group but only 5% of the bladder retrained group had excretory urogram abnormalities. Declines of more than 10% in short renal clearance values were noted in 30% of intermittent self-catheterization patients and in 15% of bladder retrained patients. Our preliminary data support the need for close surveillance and follow-up after SCI rehabilitation, even in patients appearing clinically well. These data also suggest that renal function can be preserved with current bladder management methods, with bladder retraining having a slight edge over intermittent self-catheterization.

Measurement of trunk flexibility in normal subjects: reproducibility of three clinical methods

Although measurements of trunk flexibility are an important part of a clinical examination, subjective methods are usually used to assess spinal mobility. We studied three easily performed objective techniques for determining trunk flexibility (the common "fingertip-to-floor" test, the modified Schober and Moll tests, and the Loebl inclinometer method) and their interexaminer and intraexaminer reproducibility. On 3 different days, each of 25 normal subjects was tested by the same investigator. In 25 other subjects, the studies were performed by a different examiner (one of three) on each of 3 days. We recorded the following mean coefficients of variation for interexaminer and intraexaminer reproducibility of results, respectively: fingertip-to-floor, 83% and 76.4%; flexion (Schober), 6.3% and 6.6%; right lateral flexion (Moll), 11.9% and 8.9%; left lateral flexion (Moll), 10.2% and 9.5%; extension (Moll), 9.5% and 7.3%; lumbar flexion (Loebl), 9.6% and 13.4%; and lumbar extension (Loebl), 65.4% and 50.7%. Although the reproducibility of the "fingertip-to-floor" test and the Loebl extension test was poor, all other tests studied had good reproducibility. The consistency of results with repeated testing should be considered in the application of various trunk flexibility tests to clinical and research data.

Energy expenditure in patients with low-, mid-, or high-thoracic paraplegia using Scott-Craig knee-ankle-foot orthoses

Renewed interest in ambulation in patients with paraplegia prompted us to measure the energy expenditure (kcal/kg per min) during standing and ambulating with the Scott-Craig orthosis in nine patients who had low-, mid-, or high-thoracic paraplegia. Energy expenditure during standing and during ambulation with a walker was similar for patients with all levels of paraplegia. In patients with high-thoracic paraplegia, energy efficiency was significantly less (P less than 0.05) than that for patients with mid- or low-thoracic paraplegia, whose efficiency levels were similar. In patients with low-thoracic paraplegia, the only patients who could perform swing-through gait patterns, energy efficiency was increased because of increased velocity. Our data do not support the concept of denying, on the basis of the level of the lesion alone, young, otherwise healthy, well-motivated patients with thoracic paraplegia the opportunity of using Scott-Craig orthoses to supplement wheelchair mobility and activities of daily living.

Paraplegic energy expenditure during negotiation of architectural barriers

Long-leg braces are often used by persons with paraplegia to negotiate architectural barriers, and thereby increase their wheelchair mobility. Such barriers include ramps, stairways, and narrow corridors requiring multiple turns. This study was designed to measure the energy expenditure during such activities for two long-leg orthoses: standard braces without a dorsiflexion stop and Scott-Craig braces. Energy expenditure was measured in eight subjects by indirect spirometry using Douglas bag collection and Haldane analysis. Data obtained were used to calculate oxygen consumption per minute, volume of oxygen per turn, step, or meter, and calories per minute during each activity. Using Scott-Craig braces on one day and standard braces on another day, each subject negotiated five 90 degrees turns and two 180 degree turns, ten 15.24 cm steps, both up and down, and an 11.9 m ramp inclined 12 degrees, both up and down. Milliliters of oxygen consumed per kilogram of body weight per turn, step, or meter were recorded for Scott-Craig braces, standard braces, and normal walking. All of these activities required a high expenditure of energy. No significant difference was apparent between the standard and the Scott-Craig braces for any activity.