Loss-of-function alanyl-tRNA synthetase mutations cause an autosomal-recessive early-onset epileptic encephalopathy with persistent myelination defect.

Mutations in genes encoding aminoacyl-tRNA synthetases are known to cause leukodystrophies and genetic leukoencephalopathies-heritable disorders that result in white matter abnormalities in the central nervous system. Here we report three individuals (two siblings and an unrelated individual) with severe infantile epileptic encephalopathy, clubfoot, absent deep tendon reflexes, extrapyramidal symptoms, and persistently deficient myelination on MRI. Analysis by whole exome sequencing identified mutations in the nuclear-encoded alanyl-tRNA synthetase (AARS) in these two unrelated families: the two affected siblings are compound heterozygous for p.Lys81Thr and p.Arg751Gly AARS, and the single affected child is homozygous for p.Arg751Gly AARS. The two identified mutations were found to result in a significant reduction in function. Mutations in AARS were previously associated with an autosomal-dominant inherited form of axonal neuropathy, Charcot-Marie-Tooth disease type 2N (CMT2N). The autosomal-recessive AARS mutations identified in the individuals described here, however, cause a severe infantile epileptic encephalopathy with a central myelin defect and peripheral neuropathy, demonstrating that defects of alanyl-tRNA charging can result in a wide spectrum of disease manifestations.

Mutations in SZT2 result in early-onset epileptic encephalopathy and leukoencephalopathy.

Early-onset epileptic encephalopathies (EOEEs) are a genetically heterogeneous collection of severe epilepsies often associated with psychomotor regression. Mutations in SZT2, a known seizure threshold regulator gene, are a newly identified cause of EOEE. We present an individual with EOEE, macrocephaly, and developmental regression with compound heterozygous mutations in SZT2 as identified by whole exome sequencing. Serial imaging characterized the novel finding of progressive loss of central myelination. This case expands our clinical understanding of the SZT2-phenotype and emphasizes the role of this gene in the diagnostic investigation for EOEE and leukoencephalopathies.

Revised consensus statement on the preventive and symptomatic care of patients with leukodystrophies.

Leukodystrophies are a broad class of genetic disorders that result in disruption or destruction of central myelination. Although the mechanisms underlying these disorders are heterogeneous, there are many common symptoms that affect patients irrespective of the genetic diagnosis. The comfort and quality of life of these children is a primary goal that can complement efforts directed at curative therapies. Contained within this report is a systems-based approach to management of complications that result from leukodystrophies. We discuss the initial evaluation, identification of common medical issues, and management options to establish a comprehensive, standardized care approach. We will also address clinical topics relevant to select leukodystrophies, such as gallbladder pathology and adrenal insufficiency. The recommendations within this review rely on existing studies and consensus opinions and underscore the need for future research on evidence-based outcomes to better treat the manifestations of this unique set of genetic disorders.

Whole exome sequencing in patients with white matter abnormalities.

Here we report whole exome sequencing (WES) on a cohort of 71 patients with persistently unresolved white matter abnormalities with a suspected diagnosis of leukodystrophy or genetic leukoencephalopathy. WES analyses were performed on trio, or greater, family groups. Diagnostic pathogenic variants were identified in 35% (25 of 71) of patients. Potentially pathogenic variants were identified in clinically relevant genes in a further 7% (5 of 71) of cases, giving a total yield of clinical diagnoses in 42% of individuals. These findings provide evidence that WES can substantially decrease the number of unresolved white matter cases. Ann Neurol 2016;79:1031-1037.

Characterization of human disease phenotypes associated with mutations in TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR, and IFIH1.

Aicardi-Goutières syndrome is an inflammatory disease occurring due to mutations in any of TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR or IFIH1. We report on 374 patients from 299 families with mutations in these seven genes. Most patients conformed to one of two fairly stereotyped clinical profiles; either exhibiting an in utero disease-onset (74 patients; 22.8% of all patients where data were available), or a post-natal presentation, usually within the first year of life (223 patients; 68.6%), characterized by a sub-acute encephalopathy and a loss of previously acquired skills. Other clinically distinct phenotypes were also observed; particularly, bilateral striatal necrosis (13 patients; 3.6%) and non-syndromic spastic paraparesis (12 patients; 3.4%). We recorded 69 deaths (19.3% of patients with follow-up data). Of 285 patients for whom data were available, 210 (73.7%) were profoundly disabled, with no useful motor, speech and intellectual function. Chilblains, glaucoma, hypothyroidism, cardiomyopathy, intracerebral vasculitis, peripheral neuropathy, bowel inflammation and systemic lupus erythematosus were seen frequently enough to be confirmed as real associations with the Aicardi-Goutieres syndrome phenotype. We observed a robust relationship between mutations in all seven genes with increased type I interferon activity in cerebrospinal fluid and serum, and the increased expression of interferon-stimulated gene transcripts in peripheral blood. We recorded a positive correlation between the level of cerebrospinal fluid interferon activity assayed within one year of disease presentation and the degree of subsequent disability. Interferon-stimulated gene transcripts remained high in most patients, indicating an ongoing disease process. On the basis of substantial morbidity and mortality, our data highlight the urgent need to define coherent treatment strategies for the phenotypes associated with mutations in the Aicardi-Goutières syndrome-related genes. Our findings also make it clear that a window of therapeutic opportunity exists relevant to the majority of affected patients and indicate that the assessment of type I interferon activity might serve as a useful biomarker in future clinical trials.

GJC2 promoter mutations causing Pelizaeus-Merzbacher-like disease.

OBJECTIVE: Pelizaeus-Merzbacher-like disease is a rare hypomyelinating leukodystrophy caused by autosomal recessive mutations in GJC2, encoding a gap junction protein essential for production of a mature myelin sheath. A previously identified GJC2 mutation (c.-167A>G) in the promoter region is hypothesized to disrupt a putative SOX10 binding site; however, the lack of additional mutations in this region and contradictory functional data have limited the interpretation of this variant. METHODS: We describe two independent Pelizaeus-Merzbacher-like disease families with a novel promoter region mutation and updated in vitro functional assays. RESULTS: A novel GJC2 mutation (c.-170A>G) in the promoter region was identified in Pelizaeus-Merzbacher-like disease patients. In vitro functional assays using human GJC2 promoter constructs demonstrated that this mutation and the previously described c.-167A>G mutation similarly diminished the transcriptional activity driven by SOX10 and the binding affinity for SOX10. INTERPRETATION: These findings support the role of GJC2 promoter mutations in Pelizaeus-Merzbacher-like disease. GJC2 promoter region mutation screening should be included in the evaluation of patients with unexplained hypomyelinating leukodystrophies.

Maternal uniparental isodisomy causing autosomal recessive GM1 gangliosidosis: a clinical report.

Uniparental disomy is a genetic cause of disease that may result in the inheritance of an autosomal recessive condition. A child with developmental delay and hypotonia was seen and found to have severely abnormal myelination. Lysosomal enzyme testing identified an isolated deficiency of beta-galactosidase. Subsequently, homozygous missense mutations in the galactosidase, beta 1 (GLB1) gene on chromosome 3 were found. Parental testing confirmed inheritance of two copies of the same mutated maternal GLB1 gene, and no paternal copy. SNP analysis was also done to confirm paternity. The patient was ultimately diagnosed with autosomal recessive GM1 gangliosidosis caused by maternal uniparental isodisomy. We provide a review of this patient and others in which uniparental disomy (UPD) of a non-imprinted chromosome unexpectedly caused an autosomal recessive condition. This is the first case of GM1 gangliosidosis reported in the literature to have been caused by UPD. It is important for genetic counselors and other health care providers to be aware of the possibility of autosomal recessive disease caused by UPD. UPD as a cause of autosomal recessive disease drastically changes the recurrence risk for families, and discussions surrounding UPD can be complex. Working with families to understand UPD when it occurs requires a secure and trusting counselor-family relationship.

Care Models and Discharge Services for Children With Medical Complexity.

BACKGROUND AND OBJECTIVES: Children with medical complexity (CMC) are high health care utilizers prompting hospitals to implement care models focused on this population, yet practices have not been evaluated on a national level. Our objective with this study is to describe the presence and structure of care models and the use of discharge services for CMC admitted to freestanding children's hospitals across the nation. METHODS: We distributed an electronic survey to 48 hospitals within the Pediatric Health Information System exploring the availability of care models and discharge services for CMC. Care models were grouped by type and number present at each institution. Discharge services were grouped by low (never, rarely), medium (sometimes), and high (most of the time, always) frequency use. RESULTS: Of 48 eligible hospitals, 33 completed the survey (69%). There were no significant differences between responders and non-responders for both hospital and patient characteristics. Most participants identified an outpatient care model (67%), whereas 21% had no dedicated care model for CMC in the inpatient or outpatient setting. High-frequency discharge services included durable medical equipment delivery, medication delivery, and communication with outpatient provider before discharge. Low-frequency discharge services included the use of a structured handoff tool for outpatient communication, personalized access plans, inpatient team follow-up with family after discharge, and the use of discharge checklists. CONCLUSIONS: Children's hospitals vary largely in care model structure and discharge services. Future work is needed to evaluate the associations between care models and discharge services for CMC with various health care outcomes.

Length of Stay and Barriers to Discharge for Technology-Dependent Children During the COVID-19 Pandemic.

BACKGROUND AND OBJECTIVE: During the coronavirus disease 2019 pandemic, technology-dependent children are at risk of encountering barriers to hospital discharge because of limits to in-home services. Transition difficulties could increase length of stay (LOS). With this study, we aim to (1) evaluate change in LOS and (2) describe barriers to hospital discharge between prepandemic and early pandemic periods for technology-dependent children. METHODS: A retrospective chart review of technology-dependent children discharged from an acute and specialty pediatric hospital within a single urban area between January 1 and May 28, 2020 was conducted. Technology dependence was defined by using a validated complex chronic condition coding system. Patients discharged prepandemic and during the pandemic were compared. Outcomes included LOS and the number and type of discharge barriers (a factor not related to a medical condition that delays discharge). Multivariate regression modeling and parametric and nonparametric analysis were used to compare cohorts. RESULTS: Prepandemic, 163 patients were discharged, and 119 were discharged during the early stages of the pandemic. The most common technology dependence was a feeding tube. The unadjusted median LOS was 7 days in both groups. After adjusting for patient-level factors, discharge during the pandemic resulted in a 32.2% longer LOS (confidence interval 2.1%-71.2%). The number of discharge barriers was high but unchanged between cohorts. Lack of a trained caregiver was more frequent during the pandemic (P = .03). CONCLUSIONS: Barriers to discharge were frequent for both cohorts. Discharge during the pandemic was associated with longer LOS. It was more difficult to identify a trained caregiver during the pandemic.

Absence of Axoglial Paranodal Junctions in a Child With CNTNAP1 Mutations, Hypomyelination, and Arthrogryposis.

Leukodystrophies and genetic leukoencephalopathies are a heterogeneous group of heritable disorders that affect the glial-axonal unit. As more patients with unsolved leukodystrophies and genetic leukoencephalopathies undergo next generation sequencing, causative mutations in genes leading to central hypomyelination are being identified. Two such individuals presented with arthrogryposis multiplex congenita, congenital hypomyelinating neuropathy, and central hypomyelination with early respiratory failure. Whole exome sequencing identified biallelic mutations in the CNTNAP1 gene: homozygous c.1163G>C (p.Arg388Pro) and compound heterozygous c.967T>C (p.Cys323Arg) and c.319C>T (p.Arg107*). Sural nerve and quadriceps muscle biopsies demonstrated progressive, severe onion bulb and axonal pathology. By ultrastructural evaluation, septate axoglial paranodal junctions were absent from nodes of Ranvier. Serial brain magnetic resonance images revealed hypomyelination, progressive atrophy, and reduced diffusion in the globus pallidus in both patients. These 2 families illustrate severe progressive peripheral demyelinating neuropathy due to the absence of septate paranodal junctions and central hypomyelination with neurodegeneration in CNTNAP1-associated arthrogryposis multiplex congenita.

Congenital disorder of glycosylation-X: clinicopathologic study of an autopsy case with distinct neuropathologic features.

Congenital disorders of glycosylation are a recently recognized group of inherited, multisystem disorders caused by aberrant biosynthesis of glycoproteins. We report the clinical and postmortem findings in a 3-year-old boy with a history of multiple medical issues including developmental delay, epilepsy, chronic protein-losing enteropathy, respiratory failure, nephropathy, coagulopathy, and cardiomyopathy. As part of the workup, isoelectric focusing for congenital disorders of glycosylation showed carbohydrate-deficient transferrin with the mono-oligo/dioligo ratio of 0.700 (normal, 0.075-0.109), indicating an increased level of abnormally glycosylated transferrin. After supportive care, he died secondary to multisystem complications of his disease. General autopsy findings were notable for micronodular liver cirrhosis with iron overload, myocardial ischemia and calcification, and hypertrophied glomeruli. Examination of the brain revealed cerebral and cerebellar atrophy, diffuse astrogliosis, and meningeal fibrosis. This article reveals complete autopsy findings of untyped congenital disorders of glycosylation, congenital disorders of glycosylation-x, with an undefined metabolic basis.

RMND1-Related Leukoencephalopathy With Temporal Lobe Cysts and Hearing Loss-Another Mendelian Mimicker of Congenital Cytomegalovirus Infection.

BACKGROUND: Leukoencephalopathy with temporal lobe cysts may be associated with monogenetic conditions such as Aicardi-Goutières syndrome or RNASET2 mutations and with congenital infections such as cytomegalovirus. In view of the fact that congenital cytomegalovirus is difficult to confirm outside the neonatal period, excluding a Mendelian disorder is extremely relevant, changing family planning and medical management in affected families. We performed diagnostic testing in individuals with leukoencephalopathy with temporal lobe cysts without a definitive diagnosis of congenital cytomegalovirus infection. METHODS: We reviewed a large-scale biorepository of patients with unsolved leukodystrophies and identified two individuals with required for meiotic nuclear division 1 (RMND1) mutations and similar magnetic resonance imaging (MRI) features, including temporal lobe cysts. Ten additional subjects with confirmed RMND1 mutations were identified as part of a separate disease specific cohort. Brain MRIs from all 12 individuals were reviewed for common neuroradiological features. RESULTS: MRI features in RMND1 mutations included temporal lobe swelling, with rarefaction and cystic evolution, enlarged tips of the temporal lobes, and multifocal subcortical white matter changes with confluent periatrial T2 signal hyperintensity. A combination of these features was present in ten of the 12 individuals reviewed. CONCLUSIONS: Despite the small number of reported individuals with RMND1 mutations, a clinically recognizable phenotype of leukoencephalopathy with temporal lobe swelling, rarefaction, and cystic changes has emerged in a subset of individuals. Careful clinical phenotyping, including for lactic acidosis, deafness, and severe muscle involvement seen in RMND1 mutation positive individuals, and MRI pattern recognition will be important in differentiating these patients from children with congenital infections like cytomegalovirus.

Identification of a novel de novo p.Phe932Ile KCNT1 mutation in a patient with leukoencephalopathy and severe epilepsy.

BACKGROUND: More than half of patients with genetic leukoencephalopathies remain without a specific diagnosis; this is particularly true in individuals with a likely primary neuronal etiology, such as those in which abnormal white matter occurs in combination with severe epilepsy. PATIENT: A child with a severe early infantile epileptic encephalopathy and abnormal myelination underwent whole exome sequencing. RESULTS: Whole exome sequencing identified a heterozygous de novo mutation in KCNT1, a sodium-gated potassium channel gene. CONCLUSIONS: Severely delayed myelination was anecdotally reported in previous patients with KCNT1 mutations. This case reinforces that KCNT1 sequencing should be included in an investigation of patients with severely delayed myelination and epilepsy.

Elevation of proinflammatory cytokines in patients with Aicardi-Goutières syndrome.

OBJECTIVE: This study explores a large panel of cytokines in plasma and CSF of patients with Aicardi-Goutières syndrome (AGS) at different ages, in order to establish signatures of cytokines most predictive of AGS. METHODS: Plasma from 22 subjects with known mutations were assayed for cytokines using the Milliplex MAP Immunobead system, and compared to results from 8 age-matched normal controls. CSF of 11 additional patients with mutation-proven AGS was tested in an identical manner and compared to results from age-matched controls. Samples were banked and analysis was carried out retrospectively. RESULTS: Significant elevations were seen in FMS-related tyrosine kinase 3 ligand, IP-10, interleukin (IL)-12p40, IL-15, tumor necrosis factor α, and soluble IL 2 receptor α in both AGS patient plasma and CSF relative to controls. Additionally, this cytokine signature was able to correctly cluster 9 of 11 AGS cases based on CSF values. While most cytokines decreased exponentially with age, a subgroup including IP-10 demonstrated persistent elevation beyond early childhood. CONCLUSION: Patients with AGS exhibit plasma and CSF elevations of proinflammatory cytokines. Selected cytokines remain persistently elevated beyond the initial disease phase. This panel of proinflammatory cytokines may be considered for use as diagnostic and therapeutic markers of disease, and may permit improved understanding of disease pathogenesis.