CDKL5 deficiency causes epileptic seizures independent of cellular mosaicism.

OBJECTIVE: In a study using a mouse model of CDKL5 deficiency disorder (CDD), seizures are specific to female mice heterozygous for Cdkl5 mutations and not observed in hemizygous knockout males or homozygous knockout females. The aim of this study was to examine whether the clinical phenotype of patients with CDD can be impacted by the type of genetic variant. METHODS: Eleven CDD patients (six females and five males) were included in this study. The molecular diagnosis of hemizygous male patients was performed using digital PCR and their clinical phenotypes were compared with those of patients with mosaic or heterozygous CDKL5 variants. The severity of clinical phenotypes was graded by using CDKL5 Developmental Score and the adapted version of the CDKL5 Clinical Severity Assessment. The effect of cellular mosaicism on the severity of CDD was studied by comparing the clinical characteristics and comorbidities between individuals with hemizygous and mosaic or heterozygous CDKL5 variants. RESULTS: One of the five male patients was mosaic for the CDKL5 variant. All patients developed seizures irrespective of their genetic status of the pathogenic variant. However, cellular mosaicism of CDKL5 deficiency was associated with lesser severity of other comorbidities such as feeding, respiratory, and visual functional impairments. SIGNIFICANCE: This study provided evidence that cellular mosaicism of CDKL5 deficiency was not necessarily required for developing epilepsy. CDD patients not only exhibited clinical features of epilepsy but also exhibited the developmental consequences arising directly from the effect of the CDKL5 pathogenic variant.

Novel ALG12 variants and hydronephrosis in siblings with impaired N-glycosylation.

BACKGROUND: ALG12-CDG is a rare autosomal recessive type I congenital disorder of glycosylation (CDG) due to pathogenic variants in ALG12 which encodes the dolichyl-P-mannose:Man-7-GlcNAc-2-PP-dolichyl-alpha-6-mannosyltransferase. Thirteen patients from unrelated 11 families have been reported, most of them result in broad multisystem manifestations with clinical variability. It is important to validate abnormal glycosylation to establish causal relationship. CASE REPORT: Here, we report two siblings with novel compound heterozygous variants in ALG12: c.443T>C, p.(Leu148Pro) and c.412_413insCGT, p.(Gln137_Phe138insSer). Both patients showed global developmental delay, microcephaly, hypotonia, failure to thrive, facial dysmorphism, skeletal malformations and coagulation abnormalities, which are common in ALG12-CDG. In addition, one of our patients showed left hydronephrosis, which is a novel clinical feature in ALG12-CDG. Brain MRI showed hypoplasia of cerebrum, brain stem and cerebellar vermis in both patients. N-glycosylation defects of trypsin digested transferrin peptides were revealed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), and electrospray ionization MS verified the lack of N-glycans in transferrin. CONCLUSIONS: The present study can add hydronephrosis to phenotypic spectrum of ALG12-CDG. Since the symptoms of ALG12-CDG are quite diverse, the combination of whole-exome sequencing and transferrin glycopeptide analysis with MS, can help diagnosis of ALG12-CDG.

Genetic and phenotypic analysis of 101 patients with developmental delay or intellectual disability using whole-exome sequencing.

Whole-exome sequencing (WES) enables identification of pathogenic variants, including copy number variants (CNVs). In this study, we performed WES in 101 Japanese patients with unexplained developmental delay (DD) or intellectual disability (ID) (63 males and 38 females), 98 of them with trio-WES. Pathogenic variants were identified in 54 cases (53.5%), including four cases with pathogenic CNVs. In one case, a pathogenic variant was identified by reanalysis of exome data; and in two cases, two molecular diagnoses were identified. Among 58 pathogenic variants, 49 variants occurred de novo in 48 patients, including two somatic variants. The accompanying autism spectrum disorder and external ear anomalies were associated with detection of pathogenic variants with odds ratios of 11.88 (95% confidence interval [CI] 2.52-56.00) and 3.46 (95% CI 1.23-9.73), respectively. These findings revealed the importance of reanalysis of WES data and detection of CNVs and somatic variants in increasing the diagnostic yield for unexplained DD/ID. In addition, genetic testing is recommended when patients suffer from the autism spectrum disorder or external ear anomalies, which potentially suggests the involvement of genetic factors associated with gene expression regulation.

POLR3A variants in striatal involvement without diffuse hypomyelination.

BACKGROUND: Biallelic variants in POLR3A encoding the largest subunit of RNA polymerase III cause POLR3-related (or 4H) leukodystrophy characterized by neurologic dysfunction, abnormal dentition, endocrine abnormalities and ocular abnormality. Recently, whole-exome sequencing enabled the discovery of POLR3A variants in cases lacking diffuse hypomyelination, the principal MRI phenotype of POLR3-related leukodystrophy. Homozygous c.1771-6C > G variants in POLR3A were recently suggested to cause striatal and red nucleus involvement without white matter involvement. CASE REPORT: Here, we report three cases in two families with biallelic POLR3A variants. We identified two sets of compound heterozygous variants in POLR3A, c.1771-6C > G and c.791C > T, p.(Pro264Leu) for family 1 and c.1771-6C > G and c.2671C > T, p.(Arg891*) for family 2. Both families had the c.1771-6C > G variant, which led to aberrant mRNA splicing. Neuropsychiatric regression and severe intellectual disability were identified in three patients. Two cases showed dystonia and oligodontia. Notably, characteristic bilateral symmetric atrophy and abnormal signal of the striatum without diffuse white matter signal change were observed in brain MRI of all three individuals. CONCLUSIONS: Striatum abnormalities may be another distinctive MRI finding associated with POLR3A variants, especially in cases including c.1771-6C > G variants and our cases can expand the phenotypic spectrum of POLR3A-related disorders.

A de novo TOP2B variant associated with global developmental delay and autism spectrum disorder.

BACKGROUND: TOP2B encodes type II topoisomerase beta, which controls topological changes during DNA transcription. TOP2B is expressed in the developing nervous system and is involved in brain development and neural differentiation. Recently, a de novo missense TOP2B variant (c.187C>T) has been identified in an individual with neurodevelopmental disorder (NDD). However, the association between TOP2B variants and NDDs remains uncertain. METHODS: Trio-based whole-exome sequencing was performed on a 7-year-old girl, presenting muscle hypotonia, stereotypic hand movements, epilepsy, global developmental delay, and autism spectrum disorder. Brain magnetic resonance images were normal. She was unable to walk independently and spoke no meaningful words. RESULTS: We found a de novo variant in TOP2B (NM_001330700.1:c.187C>T, p.(His63Tyr)), which is identical to the previous case. The clinical features of the two individuals with the c.187C>T variant overlapped. CONCLUSION: Our study supports the finding that TOP2B variants may cause NDDs.

Childhood-Onset Multifocal Motor Neuropathy With Immunoglobulin M Antibodies to Gangliosides GM1 and GM2: A Case Report and Review of the Literature.

Multifocal motor neuropathy is a rare immune-mediated neuropathy characterized by progressive asymmetric weakness and atrophy without sensory abnormalities. Although disease onset is usually in adulthood, a few childhood-onset cases have been reported. Here, we report the case of an 8-year-old boy with multifocal motor neuropathy who presented with a slowly progressive left and distal upper limb weakness without sensory loss. The initial high-dose intravenous immunoglobulin treatment significantly improved left upper limb muscle weakness. Continued monthly intravenous immunoglobulin treatment gradually improved muscle strength for several months initially. While the muscle strength decreased slightly after 8 months of therapy, it was better than that before intravenous immunoglobulin treatment. One year and eight months after the initiation of treatment, serum testing for IgM antibodies to gangliosides, GM1 and GM2, was negative. This is the first pediatric report of the serum IgM autoantibodies positive to GM1 and GM2. The clinical course is similar to that of partial intravenous immunoglobulin responders among patients with adulthood-onset multifocal motor neuropathy. Since the symptoms plateaued after the initial intravenous immunoglobulin therapy, prognosis appears to be determined by the patient's initial response to intravenous immunoglobulin treatment.

A multicenter, open-label extension study of velaglucerase alfa in Japanese patients with Gaucher disease: Results after a cumulative treatment period of 24months.

Enzyme replacement therapy (ERT) with exogenous glucocerebrosidase is indicated to treat symptomatic Gaucher disease (GD), a rare, inherited metabolic disorder. ERT with velaglucerase alfa, which is produced in a human cell line using gene activation technology, was studied in a 12-month phase III trial in Japanese patients with type 1 or 3 GD who were switched from imiglucerase ERT (n=6); the current, open-label, 12-month extension study was designed to assess longer-term safety and efficacy. Two adult and three pediatric patients (aged <18years) were enrolled into the extension study. Every-other-week intravenous infusions were administered for 63-78weeks at average doses between 51.5 and 60.7units/kg. Three non-serious adverse events were considered related to velaglucerase alfa treatment, but no patient discontinued from the study. Six serious but non-drug-related adverse events were reported. No patient tested positive for anti-velaglucerase alfa antibodies. Hemoglobin concentrations, platelet counts, and liver and spleen volumes (normalized to body weight) in these patients were generally stable over a cumulative 24-month period from the baseline of the parent trial. The data suggest that velaglucerase alfa was well tolerated and maintained clinical stability in Japanese GD patients over 2years after switching from imiglucerase. ClinicalTrials.gov identifier NCT01842841.

Novel RAB3GAP1 compound heterozygous mutations in Japanese siblings with Warburg Micro syndrome.

BACKGROUND: Warburg Micro syndrome (WARBM) is a rare autosomal recessive disease characterized by postnatal growth retardation, microcephaly, severely delayed motor and intellectual development, microcornea, congenital cataracts, optic atrophy, and hypogonadism. While WARBM is a genetically heterogeneous condition, RAB3GAP1 mutations account for ∼40% of WARBM patients, and 69 different mutations of various types (nonsense, missense, frameshift, and splice site mutations) have been identified to date. PATIENTS: Japanese siblings (a 7 years 3 months old male and a 2 years 1month old female) were found to have WARBM-compatible phenotypes. Direct sequencing of RAB3GAP1 revealed novel compound heterozygous mutations in the siblings: a paternally inherited missense mutation (c.560G>C; p.Arg187Pro) in exon 7 and a maternally derived nonsense mutation (c.1009C>T; p.Arg337Ter) in exon 12. CONCLUSION: The siblings had WARBM caused by novel mutations in RAB3GAP1. Since molecular diagnosis permits adequate genetic counseling and appropriate management for predicted complications such as adequate sex steroid supplementation therapy for hypogonadism, in addition to standard supportive therapies for developmental delay and visual dysfunction, we recommend molecular studies for this rare condition.

[Recurrent posterior reversible encephalopathy due to vasospasm and cerebral hypoperfusionin in acute leukemia: a case report].

We report the case of a 4-year-old girl who presented with recurrent posterior reversible encephalopathy syndrome (PRES). She was diagnosed with B-precursor acute lymphocytic leukemia (ALL), and was administered remission-induction chemotherapy. On day 28 of the induction therapy, she experienced seizure and prolonged unconsciousness. Blood pressure was slightly elevated. MRI revealed cortical cytotoxic edema in the right temporal and occipital lobes. In the right occipital white matter the lesion with vasogenic edema also existed. Three days later, MRI showed vasogenic edema in subcortical white matter of the right temporal right occipital and bilateral occipital lobes. The lesions had receded with time. Since the seizure occurred, the chemotherapy had been discontinued. The episodes of seizure and prolonged consciousness recurred 22 days later. MRI revealed vasogenic edema in the right occipital lobe, and MR angiography demonstrated vessel irregularity and reduced branch visualization in the middle and posterior cerebral arteries. Arterial spin-labeling (ASL) showed hypoperfusion in both occipital lobes. It suggests that vasoconstriction and hypoperfusion could lead to recurrent PRES in this case. It is possible that ASL might be more sensitive than MRI in detecting the lesions of PRES. It should be noted that PRES might recur in leukemia.