Characterization of central manifestations in patients with Niemann-Pick disease type C.

PURPOSE: Niemann-Pick disease type C (NPC) is a rare lysosomal storage disease characterized by progressive neurodegeneration and neuropsychiatric symptoms. This study investigated pathophysiological mechanisms underlying motor deficits, particularly speech production, and cognitive impairment. METHODS: We prospectively phenotyped 8 adults with NPC and age-sex-matched healthy controls using a comprehensive assessment battery, encompassing clinical presentation, plasma biomarkers, hand-motor skills, speech production, cognitive tasks, and (micro-)structural and functional central nervous system properties through magnetic resonance imaging. RESULTS: Patients with NPC demonstrated deficits in fine-motor skills, speech production timing and coordination, and cognitive performance. Magnetic resonance imaging revealed reduced cortical thickness and volume in cerebellar subdivisions (lobule VI and crus I), cortical (frontal, temporal, and cingulate gyri) and subcortical (thalamus and basal ganglia) regions, and increased choroid plexus volumes in NPC. White matter fractional anisotropy was reduced in specific pathways (intracerebellar input and Purkinje tracts), whereas diffusion tensor imaging graph theory analysis identified altered structural connectivity. Patients with NPC exhibited altered activity in sensorimotor and cognitive processing hubs during resting-state and speech production. Canonical component analysis highlighted the role of cerebellar-cerebral circuitry in NPC and its integration with behavioral performance and disease severity. CONCLUSION: This deep phenotyping approach offers a comprehensive systems neuroscience understanding of NPC motor and cognitive impairments, identifying potential central nervous system biomarkers.

Insights into the genotype-phenotype relationship of ocular manifestations in Kabuki syndrome.

We aim to assess if genotype-phenotype correlations are present within ocular manifestations of Kabuki syndrome (KS) among a large multicenter cohort. We conducted a retrospective, medical record review including clinical history and comprehensive ophthalmological examinations of a total of 47 individuals with molecularly confirmed KS and ocular manifestations at Boston Children's Hospital and Cincinnati Children's Hospital Medical Center. We assessed information regarding ocular structural, functional, and adnexal elements as well as pertinent associated phenotypic features associated with KS. For both type 1 KS (KS1) and type 2 KS (KS2), we observed more severe eye pathology in nonsense variants towards the C-terminus of each gene, KMT2D and KDM6A, respectively. Furthermore, frameshift variants appeared to be not associated with structural ocular elements. Between both types of KS, ocular structural elements were more frequently identified in KS1 compared with KS2, which only involved the optic disc in our cohort. These results reinforce the need for a comprehensive ophthalmologic exam upon diagnosis of KS and regular follow-up exams. The specific genotype may allow risk stratification of the severity of the ophthalmologic manifestation. However, additional studies involving larger cohorts are needed to replicate our observations and conduct powered analyses to more formally risk-stratify based on genotype, highlighting the importance of multicenter collaborations in rare disease research.

Congenital microgastria-limb reduction association: A case report and review of the literature.

We report a patient with phenotypic semblance to the congenital microgastria-limb reduction association (MLRD). Our patient presented with microgastria, bilateral upper limb anomalies, asplenia, solitary kidney, and mild micrognathia. In addition to the anomalies seen in our patient, MLRD has been associated with respiratory, cardiovascular, and central nervous system anomalies. MLRD is thought to arise from a developmental field defect during embryonic weeks five and six; however, no genetic cause has been elucidated. Along with our patient presentation, we review the literature to further our understanding of the MLRD phenotype spectrum.

The laboratory diagnosis of mucopolysaccharidosis III (Sanfilippo syndrome): A changing landscape.

Mucopolysaccharidosis type III (MPS III) is characterized by progressive neurological deterioration, behavioral abnormalities, a relatively mild somatic phenotype, and early mortality. Because of the paucity of somatic manifestations and the rarity of the disease, early diagnosis is often difficult. Therapy targeting the underlying disease pathophysiology may offer the greatest clinical benefit when started prior to the onset of significant neurologic sequelae. Here we review current practices in the laboratory diagnosis of MPS III in order to facilitate earlier patient identification and diagnosis. When clinical suspicion of MPS III arises, the first step is to order a quantitative assay that screens urine for the presence of glycosaminoglycan biomarkers using a spectrophotometric compound (e.g., dimethylmethylene blue). We recommend testing all patients with developmental delay and/or behavioral abnormalities as part of the diagnostic work-up because quantitative urine screening is inexpensive and non-invasive. Semi-quantitative urine screening assays using cationic dyes on filter paper (e.g., spot tests) have relatively high rates of false-positives and false-negatives and are obsolete. Of note, a negative urinary glycosaminoglycan assay does not necessarily rule out MPS because, in some patients, an overlap in excretion levels with healthy controls may occur. All urine samples that test positive for glycosaminoglycans with a quantitative assay should be confirmed by electrophoresis, thin layer chromatography, or tandem mass spectrometry, which further improves the sensitivity and specificity. The gold standard for diagnosis remains the enzyme activity assay in cultured skin fibroblasts, leukocytes, plasma, or serum, which can be used as a first-line diagnostic test in some regions. Molecular genetic analysis should be offered to all families of patients to allow genetic counseling for informed family planning. For a small number of variants, genotype-phenotype correlations are available and can offer prognostic value. Prenatal testing via enzyme activity assay in chorionic villi or amniotic fluid cells is available at a limited number of centers worldwide, but whenever possible, a molecular genetic analysis is preferred for prenatal diagnosis. To conclude, we discuss the development of newborn screening assays in dried blood spots and high-throughput methods for sequencing the protein-coding regions of the genome (whole exome sequencing) and their relevance to future changes in the MPS III diagnostic landscape.

Phenylketonuria Scientific Review Conference: state of the science and future research needs.

New developments in the treatment and management of phenylketonuria (PKU) as well as advances in molecular testing have emerged since the National Institutes of Health 2000 PKU Consensus Statement was released. An NIH State-of-the-Science Conference was convened in 2012 to address new findings, particularly the use of the medication sapropterin to treat some individuals with PKU, and to develop a research agenda. Prior to the 2012 conference, five working groups of experts and public members met over a 1-year period. The working groups addressed the following: long-term outcomes and management across the lifespan; PKU and pregnancy; diet control and management; pharmacologic interventions; and molecular testing, new technologies, and epidemiologic considerations. In a parallel and independent activity, an Evidence-based Practice Center supported by the Agency for Healthcare Research and Quality conducted a systematic review of adjuvant treatments for PKU; its conclusions were presented at the conference. The conference included the findings of the working groups, panel discussions from industry and international perspectives, and presentations on topics such as emerging treatments for PKU, transitioning to adult care, and the U.S. Food and Drug Administration regulatory perspective. Over 85 experts participated in the conference through information gathering and/or as presenters during the conference, and they reached several important conclusions. The most serious neurological impairments in PKU are preventable with current dietary treatment approaches. However, a variety of more subtle physical, cognitive, and behavioral consequences of even well-controlled PKU are now recognized. The best outcomes in maternal PKU occur when blood phenylalanine (Phe) concentrations are maintained between 120 and 360 µmol/L before and during pregnancy. The dietary management treatment goal for individuals with PKU is a blood Phe concentration between 120 and 360 µmol/L. The use of genotype information in the newborn period may yield valuable insights about the severity of the condition for infants diagnosed before maximal Phe levels are achieved. While emerging and established genotype-phenotype correlations may transform our understanding of PKU, establishing correlations with intellectual outcomes is more challenging. Regarding the use of sapropterin in PKU, there are significant gaps in predicting response to treatment; at least half of those with PKU will have either minimal or no response. A coordinated approach to PKU treatment improves long-term outcomes for those with PKU and facilitates the conduct of research to improve diagnosis and treatment. New drugs that are safe, efficacious, and impact a larger proportion of individuals with PKU are needed. However, it is imperative that treatment guidelines and the decision processes for determining access to treatments be tied to a solid evidence base with rigorous standards for robust and consistent data collection. The process that preceded the PKU State-of-the-Science Conference, the conference itself, and the identification of a research agenda have facilitated the development of clinical practice guidelines by professional organizations and serve as a model for other inborn errors of metabolism.

Bridging the gaps between the histopathological and demographic risk factors of preterm birth in a unique Miami inner-city population.

We aim to identify the link between placental histological findings and obstetric reports to determine possible risk factors of spontaneous preterm birth (SPTB). We prospectively ascertained birth records and outcomes from all deliveries in our hospital in 1 year. Records were used to determine and stratify for either full-term or preterm [spontaneous or indicated (I)] deliveries. We analyzed for risk factor association using χ(2) tests and common odds ratio estimates (SPSS v21.0). Our cohort totaled 6088 deliveries: 236 IPTB, 43 SPTB, and 5809 term births. Largely Hispanic, we determined race, parity, prenatal care access, preeclampsia, gestational diabetes, and BMI to be highly associated with SPTB (p < 0.01). Histologically, placentas of women with SPTB were twice as likely to have chronic villitis. We found that chronic villitis is associated with SPTB. Results of this study can be used in increasing the understanding of SPTB.

Lyso-globotriaosylsphingosine (lyso-Gb3) levels in neonates and adults with the Fabry disease later-onset GLA IVS4+919G>A mutation.

Lyso-globotriaosylsphingosine (lyso-Gb3) is a useful biomarker in the diagnosis and monitoring of treatment for Fabry disease. However, it is unclear whether lyso-Gb3 is elevated in patients with later-onset Fabry disease. Thus, we measured lyso-Gb3 levels from dried blood spots (DBS) from male newborns with the Fabry disease later-onset phenotype, IVS4+919G>A mutation, and their family members. The lyso-Gb3 levels were below the detection limit in normal control newborns and were slightly higher in adults. In males of all ages with the IVS4+919G>A mutation, lyso-Gb3 levels were elevated and were higher than in age-matched controls. The elevation of lyso-Gb3 levels in males with the IVS4+919G>A mutation was only slightly elevated compared with patients with the classical Fabry phenotype. The measurement of lyso-Gb3 levels is useful in the diagnosis of Fabry disease, including the later-onset phenotype. The DBS lyso-Gb3 level was not elevated in IVS4+919G>A heterozygotes, and is not useful for their diagnosis. Since lyso-Gb3 levels are elevated from birth in Fabry disease males, "an elevated lyso-Gb3 level" may be of little values for deciding when to begin enzyme replacement therapy.

A case of Aicardi syndrome associated with duplication event of Xp22 including SHOX.

BACKGROUND: Aicardi syndrome is a neurodevelopmental disorder characterized by a triad of partial or complete agenesis of the corpus callosum, infantile spasms, and pathognomonic chorioretinal lacunae. METHODS: Examination, multimodal imaging, and genetic testing were used to guide diagnosis. RESULTS: We report a case of a pediatric patient who was initially diagnosed with refractory infantile spasms. The patient was unresponsive to conventional antiepileptic therapy, and genetic testing with whole exome and mitochondrial genome sequencing could not identify the underlying cause, so vigabatrin was initiated. The ophthalmic examination under anesthesia for vigabatrin toxicity screening revealed chorioretinal atrophy in the retinal periphery of both eyes, with two 3-disc diameter chorioretinal lacunae superotemporal and inferonasal to the optic nerve in the left eye. Given the neuroimaging findings of corpus callosum hypoplasia with polymicrogyria and ocular findings, the patient was diagnosed with Aicardi syndrome. Genetic testing revealed a novel duplication event at the Xp22 locus. CONCLUSIONS: Aicardi syndrome, albeit a rare condition, should always be considered in the differential diagnosis when investigating a female child with refractory seizures in early childhood. Genetic testing may help further our understanding of AIS and the search for a genetic etiology.

Targeting neurological abnormalities in lysosomal storage diseases.

Central nervous system (CNS) abnormalities and corresponding neurological and psychiatric symptoms are frequently observed in lysosomal storage disorders (LSDs). The genetic background of individual LSDs is indeed unique to each illness. However, resulting defective lysosomal function within the CNS can transition normal cellular processes (i.e., autophagy) into aberrant mechanisms, facilitating overlapping downstream consequences including neurocircuitry dysfunction, neurodegeneration as well as sensory, motor, cognitive, and psychological symptoms. Here, the neurological and biobehavioral phenotypes of major classes of LSDs are discussed alongside therapeutic strategies in development that aim to tackle neuropathology among other disease elements. Finally, focused ultrasound blood-brain barrier opening is proposed to enhance therapeutic delivery thereby overcoming the key hurdle of central distribution of disease modifying therapies in LSDs.

From Genotype to Phenotype-A Review of Kabuki Syndrome.

Kabuki syndrome (KS) is a rare neuro-developmental disorder caused by variants in genes of histone modification, including KMT2D and KDM6A. This review assesses our current understanding of KS, which was originally named Niikawa-Kuroki syndrome, and aims to guide surveillance and medical care of affected individuals as well as identify gaps in knowledge and unmet patient needs. Ovid MEDLINE and EMBASE databases were searched from 1981 to 2021 to identify reports related to genotype and systems-based phenotype characterization of KS. A total of 2418 articles were retrieved, and 152 were included in this review, representing a total of 1369 individuals with KS. Genotype, phenotype, and the developmental and behavioral profile of KS are reviewed. There is a continuous clinical phenotype spectrum associated with KS with notable variability between affected individuals and an emerging genotype-phenotype correlation. The observed clinical variability may be attributable to differences in genotypes and/or unknown genetic and epigenetic factors. Clinical management is symptom oriented, fragmented, and lacks established clinical care standards. Additional research should focus on enhancing understanding of the burden of illness, the impact on quality of life, the adult phenotype, life expectancy and development of standard-of-care guidelines.

Lysosomal storage diseases: diagnostic confirmation and management of presymptomatic individuals.

PURPOSE: To develop educational guidelines for the diagnostic confirmation and management of individuals identified by newborn screening, family-based testing after proband identification, or carrier testing in at-risk populations, and subsequent prenatal or postnatal testing of those who are presymptomatic for a lysosomal storage disease. METHODS: Review of English language literature and discussions in a consensus development panel comprised an international group of experts in the clinical and laboratory diagnosis, treatment and management, newborn screening, and genetic aspects of lysosomal storage diseases. RESULTS: Although clinical trial and longitudinal data were used when available, the evidence in the literature is limited and consequently the recommendations must be considered as expert opinion. Guidelines were developed for Fabry, Gaucher, and Niemann-Pick A/B diseases, glycogen storage type II (Pompe disease), globoid cell leukodystrophy (Krabbe disease), metachromatic leukodystrophy, and mucopolysaccharidoses types I, II, and VI. CONCLUSION: These guidelines serve as an educational resource for confirmatory testing and subsequent clinical management of presymptomatic individuals suspected to have a lysosomal storage disease; they also help to define a research agenda for longitudinal studies such as the American College of Medical Genetics/National Institutes of Health Newborn Screening Translational Research Network.

Low levels of asymmetric dimethylarginine in children with diabetes mellitus type I compared with healthy children.

OBJECTIVE: Although high levels of asymmetric dimethylarginine (ADMA) are associated with an increased risk for vasculopathy in adults, elevated ADMA concentrations also have been found in healthy young children. Patients with diabetes mellitus type 1 (DM1) are at risk for vasculopathy, and because the function of ADMA in the development of vascular symptoms is incompletely understood, we investigated ADMA concentrations in pediatric patients with DM1 compared with healthy age- and sex-matched individuals. STUDY DESIGN: This cross-sectional study included 85 pediatric patients with DM1 and 89 age- and sex-matched healthy controls. RESULTS: ADMA concentrations were significantly lower in the patients with DM1 and were inversely correlated with hemoglobin A1c concentrations. CONCLUSIONS: Besides its vasoprotective function, nitric oxide itself may exert oxidative stress by generating free radicals. In these circumstances, ADMA would protect the system from nitric oxide overproduction and perpetuation of oxidative stress. This theory is supported by the physiologically higher ADMA concentrations in healthy children. Thus, low ADMA concentrations in children with DM1 may be an indicator of impaired protection against oxidative stress.

B4GALT1-congenital disorders of glycosylation presents as a non-neurologic glycosylation disorder with hepatointestinal involvement.

The clinical phenotype of congenital disorders of glycosylation is heterogeneous, mostly including a severe neurological involvement and multisystem disease. We identified a novel patient with a galactosyltransferase deficiency with mild hepatopathy and coagulation anomalies, but normal psychomotor development. The tissue-specific expression of the defective B4GALT1 gene correlated with the clinical phenotype.

The identification of novel mutations in the biotinidase gene using denaturing high pressure liquid chromatography (dHPLC).

Biotinidase deficiency (BD) is an autosomal recessive disorder of biotin metabolism that causes incomplete recycling of free biotin. The resulting depletion of intracellular biotin leads to impaired activities of biotin-dependent carboxylases. The ensuing clinical phenotype includes progressive neurologic deterioration with epileptic seizures, muscular hypotonia as well as skin eczema. BD may be readily diagnosed by analysing enzyme activity in dried blood spots during newborn screening but typically requires molecular confirmation. More than 100 different mutations in the biotinidase gene have been reported to date. To simplify molecular testing we have developed a rapid and accurate denaturing high pressure liquid chromatography (dHPLC) method of the promoter, 3'UTR, all exons including exon/intron boundaries as a first line screen followed by direct sequencing of the respective PCR products. To validate this method we used DNA from 23 different, newly diagnosed patients with biochemically proven BD from Austria, India, Morocco and Spain. A total of 11 mutations, missense 7, frameshift 3 and 1 nonsense, were screened. Six mutations were novel to this study. All mutations revealed distinct dHPLC pattern thus enabling their accurate detection. This study revealed that dHPLC method is robust, automated, economical and above all highly sensitive for the molecular analysis of biotinidase gene and should be used as a pre-analytical tool followed by sequencing of aberrant heteroduplex forming amplicons.

Laboratory and genetic evaluation of Gaucher disease.

Gaucher disease (GD) is an inherited lysosomal storage disorder due to deficiency of glucocerebrosidase. Diagnosis of GD may be suspected based on clinical symptoms and confirmed by the analysis of glucocerebrosidase in total white cells, mononuclear cells, fibroblasts and dried blood on filter paper. Low enzyme activities should be followed by molecular analysis of the GBA gene. Although there is no obvious genotype-phenotype correlation, the presence of p.N370S protects from neurological involvement whereas homozygosity of p.L444P mostly leads to a neuronopathic form of GD. Progressive storage of glucosylceramide in mononuclear cells and macrophages results in elevated levels of chitotriosidase and CCL18/PARC which may be used as biomarker to assess disease severity and efficacy of treatment. Chitotriosidase activities cannot be analysed in at least 6% of GD patients due to a null mutation in the corresponding gene.

Clinical Validation of Targeted and Untargeted Metabolomics Testing for Genetic Disorders: A 3 Year Comparative Study.

Global untargeted metabolomics (GUM) has entered clinical diagnostics for genetic disorders. We compared the clinical utility of GUM with traditional targeted metabolomics (TM) as a screening tool in patients with established genetic disorders and determined the scope of GUM as a discovery tool in patients with no diagnosis under investigation. We compared TM and GUM data in 226 patients. The first cohort (n = 87) included patients with confirmed inborn errors of metabolism (IEM) and genetic syndromes; the second cohort (n = 139) included patients without diagnosis who were undergoing evaluation for a genetic disorder. In patients with known disorders (n = 87), GUM performed with a sensitivity of 86% (95% CI: 78-91) compared with TM for the detection of 51 diagnostic metabolites. The diagnostic yield of GUM in patients under evaluation with no established diagnosis (n = 139) was 0.7%. GUM successfully detected the majority of diagnostic compounds associated with known IEMs. The diagnostic yield of both targeted and untargeted metabolomics studies is low when assessing patients with non-specific, neurological phenotypes. GUM shows promise as a validation tool for variants of unknown significance in candidate genes in patients with non-specific phenotypes.

Author Correction: Clinical Validation of Targeted and Untargeted Metabolomics Testing for Genetic Disorders: A 3 Year Comparative Study.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Development and evaluation of quality control dried blood spot materials in newborn screening for lysosomal storage disorders.

BACKGROUND: Lysosomal storage disorders (LSDs) comprise more than 40 genetic diseases that result in the accumulation of products that would normally be degraded by lysosomal enzymes. A tandem mass spectrometry (MS/MS)-based method is available for newborn screening for 5 LSDs, and many laboratories are initiating pilot studies to evaluate the incorporation of this method into their screening panels. We developed and evaluated dried blood spot (DBS) QC materials for LSDs and used the MS/MS method to investigate their suitability for LSD QC monitoring. METHODS: We incubated 3.2-mm punches from DBS controls for 20-24 h with assay cocktails containing substrate and internal standard. Using MS/MS, we quantified the resulting product and internal standard. Samples were run in triplicate for 3 consecutive days, and results were reported as product-to-internal standard ratios and enzyme activity units (micromol/L/h). RESULTS: Enzyme activity interday imprecision (CV) for the high, medium, and low series were 3.4%-14.3% for galactocerebroside alpha-galactosidase, 6.8%-24.6% for acid alpha-galactosidase A, 7.36%-22.1% for acid sphingomyelinase, 6.2%-26.2% for acid alpha-glucocerebrosidase, and 7.0%-24.8% for lysosomal acid alpha-glucosidase (n = 9). In addition, DBS stored at -20 degrees and 4 degrees C showed minimal enzyme activity loss over a 187-d period. DBS stored at 37 degrees and 45 degrees C had lower activity values over the 187-day evaluation time. CONCLUSIONS: Suitable QC materials for newborn screening of LSDs were developed for laboratories performing DBS LSD screening. Good material linearity was observed, with goodness-of-fit values of 0.953 and higher. The QC materials may be used by screening laboratories that perform LSD analysis by MS and/or more conventional fluorescence-based screening methods.