Lessons learnt from multifaceted diagnostic approaches to the first 150 families in Victoria's Undiagnosed Diseases Program.

BACKGROUND: Clinical exome sequencing typically achieves diagnostic yields of 30%-57.5% in individuals with monogenic rare diseases. Undiagnosed diseases programmes implement strategies to improve diagnostic outcomes for these individuals. AIM: We share the lessons learnt from the first 3 years of the Undiagnosed Diseases Program-Victoria, an Australian programme embedded within a clinical genetics service in the state of Victoria with a focus on paediatric rare diseases. METHODS: We enrolled families who remained without a diagnosis after clinical genomic (panel, exome or genome) sequencing between 2016 and 2018. We used family-based exome sequencing (family ES), family-based genome sequencing (family GS), RNA sequencing (RNA-seq) and high-resolution chromosomal microarray (CMA) with research-based analysis. RESULTS: In 150 families, we achieved a diagnosis or strong candidate in 64 (42.7%) (37 in known genes with a consistent phenotype, 3 in known genes with a novel phenotype and 24 in novel disease genes). Fifty-four diagnoses or strong candidates were made by family ES, six by family GS with RNA-seq, two by high-resolution CMA and two by data reanalysis. CONCLUSION: We share our lessons learnt from the programme. Flexible implementation of multiple strategies allowed for scalability and response to the availability of new technologies. Broad implementation of family ES with research-based analysis showed promising yields post a negative clinical singleton ES. RNA-seq offered multiple benefits in family ES-negative populations. International data sharing strategies were critical in facilitating collaborations to establish novel disease-gene associations. Finally, the integrated approach of a multiskilled, multidisciplinary team was fundamental to having diverse perspectives and strategic decision-making.

Mosaicism in tuberous sclerosis complex: Lowering the threshold for clinical reporting.

Tuberous sclerosis complex (TSC) is a multi-system genetic disorder. Most patients have germline mutations in TSC1 or TSC2 but, 10%-15% patients do not have TSC1/TSC2 mutations detected on routine clinical genetic testing. We investigated the contribution of low-level mosaic TSC1/TSC2 mutations in unsolved sporadic patients and families with TSC. Thirty-one sporadic TSC patients negative on routine testing and eight families with suspected parental mosaicism were sequenced using deep panel sequencing followed by droplet digital polymerase chain reaction. Pathogenic variants were found in 22/31 (71%) unsolved sporadic patients, 16 were mosaic (median variant allele fraction [VAF] 6.8% in blood) and 6 had missed germline mutations. Parental mosaicism was detected in 5/8 families (median VAF 1% in blood). Clinical testing laboratories typically only report pathogenic variants with allele fractions above 10%. Our findings highlight the critical need to change laboratory practice by implementing higher sensitivity assays to improve diagnostic yield, inform patient management and guide reproductive counseling.

The diverse pleiotropic effects of spliceosomal protein PUF60: A case series of Verheij syndrome.

Verheij syndrome (VRJS) is a rare craniofacial spliceosomopathy presenting with craniofacial dysmorphism, multiple congenital anomalies and variable neurodevelopmental delay. It is caused by single nucleotide variants (SNVs) in PUF60 or interstitial deletions of the 8q24.3 region. PUF60 encodes a splicing factor which forms part of the spliceosome. To date, 36 patients with a sole diagnosis of VRJS due to disease-causing PUF60 SNVs have been reported in peer-reviewed publications. Although the depth of their phenotyping has varied greatly, they exhibit marked phenotypic heterogeneity. We report 10 additional unrelated patients, including the first described patients of Khmer, Indian, and Vietnamese ethnicities, and the eldest patient to date, with 10 heterozygous PUF60 variants identified through exome sequencing, 8 previously unreported. All patients underwent deep phenotyping identifying variable dysmorphism, growth delay, neurodevelopmental delay, and multiple congenital anomalies, including several unique features. The eldest patient is the only reported individual with a germline variant and neither neurodevelopmental delay nor intellectual disability. In combining these detailed phenotypic data with that of previously reported patients (n = 46), we further refine the known frequencies of features associated with VRJS. These include neurodevelopmental delay/intellectual disability (98%), axial skeletal anomalies (74%), appendicular skeletal anomalies (73%), oral anomalies (68%), short stature (66%), cardiac anomalies (63%), brain malformations (48%), hearing loss (46%), microcephaly (41%), colobomata (38%), and other ocular anomalies (65%). This case series, incorporating three patients from previously unreported ethnic backgrounds, further delineates the broad pleiotropy and mutational spectrum of PUF60 pathogenic variants.

Expanding the clinical and radiological phenotypes of leukoencephalopathy due to biallelic HMBS mutations.

Pathogenic heterozygous variants in HMBS encoding the enzyme hydroxymethylbilane synthase (HMBS), also known as porphobilinogen deaminase, cause acute intermittent porphyria (AIP). Biallelic variants in HMBS have been reported in a small number of children with severe progressive neurological disease and in three adult siblings with a more slowly, progressive neurological disease and distinct leukoencephalopathy. We report three further adult individuals who share a distinct pattern of white matter abnormality on brain MRI in association with biallelic variants in HMBS, two individuals with homozygous variants, and one with compound-heterozygous variants. We present their clinical and radiological features and compare these with the three adult siblings previously described with leukoencephalopathy and biallelic HMBS variants. All six affected individuals presented with slowly progressive spasticity, ataxia, peripheral neuropathy, with or without mild cognitive impairment, and/or ocular disease with onset in childhood or adolescence. Their brain MRIs show mainly confluent signal abnormalities in the periventricular and deep white matter and bilateral thalami. This recognizable pattern of MRI abnormalities is seen in all six adults described here. Biallelic variants in HMBS cause a phenotype that is distinct from AIP. It is not known whether AIP treatments benefit individuals with HMBS-related leukoencephalopathy. One individual reported here had improved neurological function for 12 months following liver transplantation followed by decline and progression of disease.

The recurrent postzygotic pathogenic variant p.Glu47Lys in RHOA causes a novel recognizable neuroectodermal phenotype.

RHOA is a member of the Rho family of GTPases that are involved in fundamental cellular processes including cell adhesion, migration, and proliferation. RHOA can stimulate the formation of stress fibers and focal adhesions and is a key regulator of actomyosin dynamics in various tissues. In a Genematcher-facilitated collaboration, we were able to identify four unrelated individuals with a specific phenotype characterized by hypopigmented areas of the skin, dental anomalies, body asymmetry, and limb length discrepancy due to hemihypotrophy of one half of the body, as well as brain magnetic resonance imaging (MRI) anomalies. Using whole-exome and ultra-deep amplicon sequencing and comparing genomic data of affected and unaffected areas of the skin, we discovered that all four individuals carried the identical RHOA missense variant, c.139G>A; p.Glu47Lys, in a postzygotic state. Molecular modeling and in silico analysis of the affected p.Glu47Lys residue in RHOA indicated that this exchange is predicted to specifically alter the interaction of RHOA with its downstream effectors containing a PKN-type binding domain and thereby disrupts its ability to activate signaling. Our findings indicate that the recurrent postzygotic RHOA missense variant p.Glu47Lys causes a specific mosaic disorder in humans.

Expanding the clinical and genetic spectrum of ALPK3 variants: Phenotypes identified in pediatric cardiomyopathy patients and adults with heterozygous variants.

INTRODUCTION: Biallelic damaging variants in ALPK3, encoding alpha-protein kinase 3, cause pediatric-onset cardiomyopathy with manifestations that are incompletely defined. METHODS AND RESULTS: We analyzed clinical manifestations of damaging biallelic ALPK3 variants in 19 pediatric patients, including nine previously published cases. Among these, 11 loss-of-function (LoF) variants, seven compound LoF and deleterious missense variants, and one homozygous deleterious missense variant were identified. Among 18 live-born patients, 8 exhibited neonatal dilated cardiomyopathy (44.4%; 95% CI: 21.5%-69.2%) that subsequently transitioned into ventricular hypertrophy. The majority of patients had extracardiac phenotypes, including contractures, scoliosis, cleft palate, and facial dysmorphisms. We observed no association between variant type or location, disease severity, and/or extracardiac manifestations. Myocardial histopathology showed focal cardiomyocyte hypertrophy, subendocardial fibroelastosis in patients under 4 years of age, and myofibrillar disarray in adults. Rare heterozygous ALPK3 variants were also assessed in adult-onset cardiomyopathy patients. Among 1548 Dutch patients referred for initial genetic analyses, we identified 39 individuals with rare heterozygous ALPK3 variants (2.5%; 95% CI: 1.8%-3.4%), including 26 missense and 10 LoF variants. Among 149 U.S. patients without pathogenic variants in 83 cardiomyopathy-related genes, we identified six missense and nine LoF ALPK3 variants (10.1%; 95% CI: 5.7%-16.1%). LoF ALPK3 variants were increased in comparison to matched controls (Dutch cohort, P = 1.6×10-5; U.S. cohort, P = 2.2×10-13). CONCLUSION: Biallelic damaging ALPK3 variants cause pediatric cardiomyopathy manifested by DCM transitioning to hypertrophy, often with poor contractile function. Additional extracardiac features occur in most patients, including musculoskeletal abnormalities and cleft palate. Heterozygous LoF ALPK3 variants are enriched in adults with cardiomyopathy and may contribute to their cardiomyopathy. Adults with ALPK3 LoF variants therefore warrant evaluations for cardiomyopathy.

A cost-effectiveness analysis of genomic sequencing in a prospective versus historical cohort of complex pediatric patients.

PURPOSE: Cost-effectiveness evaluations of first-line genomic sequencing (GS) in the diagnosis of children with genetic conditions are limited by the lack of well-defined comparative cohorts. We sought to evaluate the cost-effectiveness of early GS in pediatric patients with complex monogenic conditions compared with a matched historical cohort. METHODS: Data, including investigation costs, were collected in a prospective cohort of 92 pediatric patients undergoing singleton GS over an 18-month period (2016-2017) with two of the following: a condition with high mortality, multisystem disease involving three or more organs, or severe limitation of daily function. Comparative data were collected in a matched historical cohort who underwent traditional investigations in the years 2012-2013. RESULTS: GS yielded a diagnosis in 42% while traditional investigations yielded a diagnosis in 23% (p = 0.003). A change in management was experienced by 74% of patients diagnosed following GS, compared with 32% diagnosed following traditional investigations. Singleton GS at a cost of AU$3100 resulted in a mean saving per person of AU$3602 (95% confidence interval [CI] AU$2520-4685). Cost savings occurred across all investigation subtypes and were only minimally offset by clinical management costs. CONCLUSION: GS in complex pediatric patients saves significant costs and doubles the diagnostic yield of traditional approaches.

Revealing hidden genetic diagnoses in the ocular anterior segment disorders.

PURPOSE: Ocular anterior segment disorders (ASDs) are clinically and genetically heterogeneous, and genetic diagnosis often remains elusive. In this study, we demonstrate the value of a combined analysis protocol using phenotypic, genomic, and pedigree structure data to achieve a genetic conclusion. METHODS: We utilized a combination of chromosome microarray, exome sequencing, and genome sequencing with structural variant and trio analysis to investigate a cohort of 41 predominantly sporadic cases. RESULTS: We identified likely causative variants in 54% (22/41) of cases, including 51% (19/37) of sporadic cases and 75% (3/4) of cases initially referred as familial ASD. Two-thirds of sporadic cases were found to have heterozygous variants, which in most cases were de novo. Approximately one-third (7/22) of genetic diagnoses were found in rarely reported or recently identified ASD genes including PXDN, GJA8, COL4A1, ITPR1, CPAMD8, as well as the new phenotypic association of Axenfeld-Rieger anomaly with a homozygous ADAMTS17 variant. The remainder of the variants were in key ASD genes including FOXC1, PITX2, CYP1B1, FOXE3, and PAX6. CONCLUSIONS: We demonstrate the benefit of detailed phenotypic, genomic, variant, and segregation analysis to uncover some of the previously "hidden" heritable answers in several rarely reported and newly identified ocular ASD-related disease genes.

Cerebral hypomyelination associated with biallelic variants of FIG4.

The lipid phosphatase gene FIG4 is responsible for Yunis-Varón syndrome and Charcot-Marie-Tooth disease Type 4J, a peripheral neuropathy. We now describe four families with FIG4 variants and prominent abnormalities of central nervous system (CNS) white matter (leukoencephalopathy), with onset in early childhood, ranging from severe hypomyelination to mild undermyelination, in addition to peripheral neuropathy. Affected individuals inherited biallelic FIG4 variants from heterozygous parents. Cultured fibroblasts exhibit enlarged vacuoles characteristic of FIG4 dysfunction. Two unrelated families segregate the same G > A variant in the +1 position of intron 21 in the homozygous state in one family and compound heterozygous in the other. This mutation in the splice donor site of exon 21 results in read-through from exon 20 into intron 20 and truncation of the final 115 C-terminal amino acids of FIG4, with retention of partial function. The observed CNS white matter disorder in these families is consistent with the myelination defects in the FIG4 null mouse and the known role of FIG4 in oligodendrocyte maturation. The families described here the expanded clinical spectrum of FIG4 deficiency to include leukoencephalopathy.

Neonatal detection of Aicardi Goutières Syndrome by increased C26:0 lysophosphatidylcholine and interferon signature on newborn screening blood spots.

BACKGROUND: Aicardi Goutières Syndrome (AGS) is a heritable interferonopathy associated with systemic autoinflammation causing interferon (IFN) elevation, central nervous system calcifications, leukodystrophy and severe neurologic sequelae. An infant with TREX1 mutations was recently found to have abnormal C26:0 lysophosphatidylcholine (C26:0 Lyso-PC) in a newborn screening platform for X-linked adrenoleukodystrophy, prompting analysis of this analyte in retrospectively collected samples from individuals affected by AGS. METHODS: In this study, we explored C26:0 Lyso-PC levels and IFN signatures in newborn blood spots and post-natal blood samples in 19 children with a molecular and clinical diagnosis of AGS and in the blood spots of 22 healthy newborns. We used Nanostring nCounter™ for IFN-induced gene analysis and a high-performance liquid chromatography with tandem mass spectrometry (HPLC MS/MS) newborn screening platform for C26:0 Lyso-PC analysis. RESULTS: Newborn screening cards from patients across six AGS associated genes were collected, with a median disease presentation of 2months. Thirteen out of 19 (68%) children with AGS had elevations of first tier C26:0 Lyso-PC (>0.4µM), that would have resulted in a second screen being performed in a two tier screening system for X-linked adrenoleukodystrophy (X-ALD). The median (95%CI) of first tier C26:0 Lyso-PC values in AGS individuals (0.43µM [0.37-0.48]) was higher than that seen in controls (0.21µM [0.21-0.21]), but lower than X-ALD individuals (0.72µM [0.59-0.84])(p<0.001). Fourteen of 19 children had elevated expression of IFN signaling on blood cards relative to controls (Sensitivity 73.7%, 95%CI 51-88%, Specificity 95%, 95% CI 78-99%) including an individual with delayed disease presentation (36months of age). All five AGS patients with negative IFN signature at birth had RNASEH2B mutations. Consistency of agreement between IFN signature in neonatal and post-natal samples was high (0.85). CONCLUSION: This suggests that inflammatory markers in AGS can be identified in the newborn period, before symptom onset. Additionally, since C26:0 Lyso-PC screening is currently used in X-ALD newborn screening panels, clinicians should be alert to the fact that AGS infants may present as false positives during X-ALD screening.

Advances in genomic testing.

BACKGROUND: Advances in genomic technology and our understanding of Mendelian disease-causing genes have led to an increased use of genomic testing in clinical practice. OBJECTIVE: The aim of this paper is to outline recent advances in genetic and genomic testing and the implications for clinical practice. DISCUSSION: Next-generation genomic sequencing is improving the diagnostic yield for patients with suspected genetic disease. A molecular diagnosis for a patient with genetic disease can provide information regarding a patient's prognosis, management and reproductive risk, and identify molecular targets for treatment. However, genomic testing frequently identifies variants of uncertain significance. This is illustrated by two case examples.

Polymicrogyria: a common and heterogeneous malformation of cortical development.

Polymicrogyria (PMG) is one of the most common malformations of cortical development. It is characterized by overfolding of the cerebral cortex and abnormal cortical layering. It is a highly heterogeneous malformation with variable clinical and imaging features, pathological findings, and etiologies. It may occur as an isolated cortical malformation, or in association with other malformations within the brain or body as part of a multiple congenital anomaly syndrome. Polymicrogyria shows variable topographic patterns with the bilateral perisylvian pattern being most common. Schizencephaly is a subtype of PMG in which the overfolded cortex lines full-thickness clefts connecting the subarachnoid space with the cerebral ventricles. Both genetic and non-genetic causes of PMG have been identified. Non-genetic causes include congenital cytomegalovirus infection and in utero ischemia. Genetic causes include metabolic conditions such as peroxisomal disorders and the 22q11.2 and 1p36 continguous gene deletion syndromes. Mutations in over 30 genes have been found in association with PMG, especially mutations in the tubulin family of genes. Mutations in the (PI3K)-AKT pathway have been found in association PMG and megalencephaly. Despite recent genetic advances, the mechanisms by which polymicrogyric cortex forms and causes of the majority of cases remain unknown, making diagnostic and prenatal testing and genetic counseling challenging. This review summarizes the clinical, imaging, pathologic, and etiologic features of PMG, highlighting recent genetic advances.

Comparing saliva and blood for the detection of mosaic genomic abnormalities that cause syndromic intellectual disability.

We aimed to determine whether SNP-microarray genomic testing of saliva had a greater diagnostic yield than blood for pathogenic copy number variants (CNVs). We selected patients who underwent CMA testing of both blood and saliva from 23,289 blood and 21,857 saliva samples. Our cohort comprised 370 individuals who had testing of both, 224 with syndromic intellectual disability (ID) and 146 with isolated ID. Mosaic pathogenic CNVs or aneuploidy were detected in saliva but not in blood in 20/370 (4.4%). All 20 individuals had syndromic ID, accounting for 9.1% of the syndromic ID sub-cohort. Pathogenic CNVs were large in size (median of 46 Mb), and terminal in nature, with median mosaicism of 27.5% (not exceeding 40%). By contrast, non-mosaic pathogenic CNVs were 100% concordant between blood and saliva, considerably smaller in size (median of 0.65 Mb), and predominantly interstitial in location. Given that salivary microarray testing has increased diagnostic utility over blood in individuals with syndromic ID, we recommend it as a first-tier testing in this group.

Investigating disparity in access to Australian clinical genetic health services for Aboriginal and Torres Strait Islander people.

Globally, there is a recognised need that all populations should be able to access the benefits of genomics and precision medicine. However, achieving this remains constrained by a paucity of data that quantifies access to clinical genomics, particularly amongst Indigenous populations. Using administrative data from clinical genetic health services across three Australian jurisdictions (states/territories), we investigate disparities in the scheduling and attendance of appointments among Aboriginal and/or Torres Strait Islander people, compared to non-Indigenous people. For 14,870 appointments scheduled between 2014-2018, adjusted Multivariate Poisson Regression models revealed that Aboriginal and/or Torres Strait Islander people were scheduled fewer appointments (IRR 0.73 [0.68-0.80], <0.001) and attended at lower rates (IRR 0.85 [0.78-0.93], <0.001). Within this population, adults, females, remote residents, and those presenting in relation to cancer or prenatal indications experienced the greatest disparity in access. These results provide important baseline data related to disparities in access to clinical genomics in Australia.

Somatic IDH1 variant (p.R132C) in an adult male with Maffucci syndrome.

Maffucci syndrome is a rare, highly variable somatic mosaic condition, and well-known cancer-related gain-of-function variants in either the IDH1 or IDH2 genes have been found in the affected tissues of most reported individuals. Features include benign enchondroma and spindle-cell hemangioma, with a recognized increased risk of various malignancies. Fewer than 200 affected individuals have been reported; therefore, accurate estimates of malignancy risk are difficult to quantify and recommended surveillance guidelines are not available. The same gain-of-function IDH1 and IDH2 variants are also implicated in a variety of other benign and malignant tumors. An adult male presented with several soft palpable lesions on the right upper limb. Imaging and histopathology raised the possibility of Maffucci syndrome. DNA was extracted from peripheral blood lymphocytes and tissue surgically resected from a spindle-cell hemangioma. Sanger sequencing and droplet digital polymerase chain reaction (PCR) analysis of the IDH1 gene were performed. We identified a somatic mosaic c.394C > T (p.R132C) variant in exon 5 of IDH1, in DNA derived from hemangioma tissue at ∼17% variant allele fraction. This variant was absent in DNA derived from blood. This variant has been identified in the affected tissue of most reported individuals with Maffucci syndrome. Although this individual has a potentially targetable variant, and there is a recognized risk of malignant transformation in this condition, a decision was made not to intervene with an IDH1 inhibitor. The reasons and prospects for therapy in this condition are discussed.

Speech, Language, and Oromotor Skills in Patients With Polymicrogyria.

OBJECTIVE: To determine whether specific speech, language, and oromotor profiles are associated with different patterns of polymicrogyria, we assessed 52 patients with polymicrogyria using a battery of standardized tests and correlated findings with topography and severity of polymicrogyria. METHODS: Patients were identified via clinical research databases and invited to participate, irrespective of cognitive and verbal language abilities. We conducted standardized assessments of speech, oromotor structure and function, language, and nonverbal IQ. Data were analyzed according to normative assessment data and descriptive statistics. We conducted a correlation analysis between topographic pattern and speech and language findings. RESULTS: Fifty-two patients (33 male, 63%) were studied at an average age of 12.7 years (range 2.5-36 years). All patients had dysarthria, which ranged from mild impairment to anarthria. Developmental speech errors (articulation and phonology), oral motor structure and function deficits, and language disorder were frequent. A total of 23/29 (79%) had cognitive abilities in the low average to extremely low range. In the perisylvian polymicrogyria group (36/52), speech, everyday language, and oral motor impairments were more severe, compared to generalized (1 patient), frontal (3), polymicrogyria with periventricular nodular heterotopia (3), parasagittal parieto-occipital (1), mesial occipital (1), and other (7) patterns. CONCLUSIONS: Dysarthria is a core feature of polymicrogyria, often accompanied by receptive and expressive language impairments. These features are associated with all polymicrogyria distribution patterns and more severe in individuals with bilateral polymicrogyria, particularly in the perisylvian region.

Genetic heterogeneity of polymicrogyria: study of 123 patients using deep sequencing.

Polymicrogyria is a malformation of cortical development characterized by overfolding and abnormal lamination of the cerebral cortex. Manifestations include epilepsy, speech disturbance and motor and cognitive disability. Causes include acquired prenatal insults and inherited and de novo genetic variants. The proportion of patients with polymicrogyria and a causative germline or mosaic variant is not known. The aim of this study was to identify the monogenic causes of polymicrogyria in a heterogeneous cohort of patients reflective of specialized referral services. Patients with polymicrogyria were recruited from two clinical centres in Australia and Belgium. Patients with evidence of congenital cytomegalovirus infection or causative chromosomal copy number variants were excluded. One hundred and twenty-three patients were tested using deep sequencing gene panels including known and candidate genes for malformations of cortical development. Causative and potentially causative variants were identified and correlated with phenotypic features. Pathogenic or likely pathogenic variants were identified in 25/123 (20.3%) patients. A candidate variant was identified for an additional patient but could not be confirmed as de novo, and therefore it was classified as being of uncertain significance with high clinical relevance. Of the 22 dominant variants identified, 5 were mosaic with allele fractions less than 0.33 and the lowest allele fraction 0.09. The most common causative genes were TUBA1A and PIK3R2. The other eleven causative genes were PIK3CA, NEDD4L, COL4A1, COL4A2, GPSM2, GRIN2B, WDR62, TUBB3, TUBB2B, ACTG1 and FH. A genetic cause was more likely to be identified in the presence of an abnormal head size or additional brain malformations suggestive of a tubulinopathy, such as dysmorphic basal ganglia. A gene panel test provides greater sequencing depth and sensitivity for mosaic variants than whole exome or genome sequencing but is limited to the genes included, potentially missing variants in newly discovered genes. The diagnostic yield of 20.3% indicates that polymicrogyria may be associated with genes not yet known to be associated with brain malformations, brain-specific somatic mutations or non-genetic causes.

Chudley-McCullough Syndrome: A Recognizable Clinical Entity Characterized by Deafness and Typical Brain Malformations.

Chudley-McCullough syndrome, a rare autosomal recessive disorder due to pathogenic variants in the GPSM2 (G-protein signaling modulator 2) gene, is characterized by early-onset sensorineural deafness and a typical combination of brain malformations, including ventriculomegaly, (partial) agenesis of the corpus callosum, cerebellar dysplasia, arachnoid cysts, frontal subcortical heterotopia, and midline polymicrogyria. When hearing loss is managed early, most patients have minor or no impairment of motor and cognitive development, despite the presence of brain malformations. We report 2 cases of Chudley-McCullough syndrome, one presenting with congenital deafness and normal development except for speech delay and one presenting prenatally with ventriculomegaly and an atypical postnatal course characterized by epileptic spasms, deafness, and moderate intellectual disability. These highlight the challenges faced by clinicians when predicting prognosis based on pre- or postnatal imaging of brain malformations. We have also reviewed the phenotype and genotype of previous published cases to better understand Chudley-McCullough syndrome.

Phenotypic Spectrum of Seizure Disorders in MBD5-Associated Neurodevelopmental Disorder.

OBJECTIVE: To describe the phenotypic spectrum in patients with MBD5-associated neurodevelopmental disorder (MAND) and seizures; features of MAND include intellectual disability, epilepsy, psychiatric features of aggression and hyperactivity, and dysmorphic features including short stature and microcephaly, sleep disturbance, and ataxia. METHODS: We performed phenotyping on patients with MBD5 deletions, duplications, or point mutations and a history of seizures. RESULTS: Twenty-three patients with MAND and seizures were included. Median seizure onset age was 2.9 years (range 3 days-13 years). The most common seizure type was generalized tonic-clonic; focal, atypical absence, tonic, drop attacks, and myoclonic seizures occurred frequently. Seven children had convulsive status epilepticus and 3 nonconvulsive status epilepticus. Fever, viral illnesses, and hot weather provoked seizures. EEG studies in 17/21 patients were abnormal, typically showing slow generalized spike-wave and background slowing. Nine had drug-resistant epilepsy, although 3 eventually became seizure-free. All but one had moderate-to-severe developmental impairment. Epilepsy syndromes included Lennox-Gastaut syndrome, myoclonic-atonic epilepsy, and infantile spasms syndrome. Behavioral problems in 20/23 included aggression, self-injurious behavior, and sleep disturbance. CONCLUSIONS: MBD5 disruption may be associated with severe early childhood-onset developmental and epileptic encephalopathy. Because neuropsychiatric dysfunction is common and severe, it should be an important focus of clinical management.

Further Delineation of the Clinical and Pathologic Features of HIKESHI-Related Hypomyelinating Leukodystrophy.

BACKGROUND: A recurrent homozygous missense variant, c.160G>C;p.(Val54Leu) in HIKESHI, was found to cause a hypomyelinating leukodystrophy with high frequency in the Ashkenazi Jewish population. We provide extended phenotypic classification of this disorder based on clinical history of a further seven affected individuals, assess carrier frequency in the Ashkenazi Jewish population, and provide a neuropathological study. METHODS: Clinical information, neuroimaging, and biosamples were collected. Brain autopsy was performed for one case. RESULTS: Individuals with HIKESHI-related disease share common clinical features: early axial hypotonia evolving to dystonia or with progressive spasticity, hyperreflexia and clonus, feeding difficulties with poor growth, and nystagmus. Severe morbidity or death during febrile illness occurred in five of the nine affected individuals. Magnetic resonance images of seven patients were analyzed and demonstrated diffuse hypomyelination and thin corpus callosum. Genotyping data of more than 125,000 Ashkenazi Jewish individuals revealed a carrier frequency of 1 in 216. Gross pathology examination in one case revealed abnormal white matter. Microscopically, there was a near-total absence of myelin with a relative preservation of axons. The cerebral white matter showed several reactive astrocytes and microglia. CONCLUSIONS: We provide pathologic evidence for a primary disorder of the myelin in HIKESHI-related leukodystrophy. These findings are consistent with the hypomyelination seen in brain magnetic resonance imaging and with the clinical features of early-onset spastic/dystonic quadriplegia and nystagmus. The high carrier rate of the recurrent variant seen in the Ashkenazi Jewish population requires increased attention to screening and diagnosis of this condition, particularly in this population.