Neuropathological characterization of the cavitating leukoencephalopathy caused by COA8 cytochrome c oxidase deficiency: a case report.

COA8-related leukoencephalopathy is a recently described rare cavitating leukoencephalopathy caused by biallelic variants in the COA8 gene. Clinically, it presents heterogeneously and usually follows a bi-phasic clinical course with a period of acute onset and regression, followed by stabilization, and in some cases, even subtle improvement. We present a 4-year-old boy with a homozygous 2.5 kilobase pair deletion in the COA8 gene following a severe neurological deterioration resulting in death weeks after onset. Brain MRI revealed a distinctive pattern of cavitating leukodystrophy predominantly involving the posterior cerebral white matter which improved upon a follow-up MRI a month later. Brain pathology displayed overall white matter destruction with gliosis and infiltration by macrophages. There was preservation of astrocytes around blood vessels and axons around the zones of demyelination. This study is the first neuropathological examination of COA8-related leukoencephalopathy and provides further characterization of the clinical and MRI phenotype.

The Experience of Parents of Children With Genetically Determined Leukoencephalopathies With the Health Care System: A Qualitative Study.

Parents of children with genetically determined leukoencephalopathies play a major role in their children's health care. We sought to gain a better understanding of their experience with the public health care system in Quebec, Canada, to obtain suggestions for improving their services, and to identify modifiable factors to improve their quality of life. We conducted interviews with 13 parents. Data was analyzed thematically. Five themes were identified: challenges of the diagnostic odyssey, limited access to services, excessive parental responsibilities, positive relationships with health care professionals as a facilitator of care, and benefits of a specialized leukodystrophy clinic. Parents felt like waiting for the diagnosis was extremely stressful, and they expressed their need for transparency during this period. They identified multiple gaps and barriers in the health care system, which burdened them with many responsibilities. Parents emphasized the importance of a positive relationship with their child's health care professionals. They also felt grateful for being followed at a specialized clinic as it improved the quality of care received.

Experience of Parents of Children with Genetically Determined Leukoencephalopathies Regarding the Adapted Health Care Services During the COVID-19 Pandemic.

Parents of children with genetically determined leukoencephalopathies play a major role in their children's health care. Because of the COVID-19 pandemic, many health care services were suspended, delayed or delivered remotely with telemedicine. We sought to explore the experience of parents of children with genetically determined leukoencephalopathies during the pandemic given the adapted health care services. We conducted semistructured interviews with 13 parents of 13 affected children. Three main themes were identified using thematic analysis: perceived impact of COVID-19 on health care services, benefits and challenges of telemedicine, and expectations of health care after the pandemic. Parents perceived a loss/delay in health care services while having a positive response to telemedicine. Parents wished telemedicine would remain in their care after the pandemic. This is the first study assessing the impact of COVID-19 on health care services in this population. Our results suggest that parents experience a higher level of stress owing to the shortage of services and the children's vulnerability.

HSD10 mitochondrial disease: p.Leu122Val variant, mild clinical phenotype, and founder effect in French-Canadian patients from Quebec.

BACKGROUND: HSD10 mitochondrial disease (HSD10MD), originally described as a deficiency of 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD), is a rare X-linked disorder of a moonlighting protein encoded by the HSD17B10. The diagnosis is usually first suspected on finding elevated isoleucine degradation metabolites in urine, reflecting decreased MHBD activity. However, it is now known that clinical disease pathogenesis reflects other independent functions of the HSD10 protein; particularly its essential role in mitochondrial transcript processing and tRNA maturation. The classical phenotype of HSD10MD in affected males is an infantile-onset progressive neurodegenerative disorder associated with severe mitochondrial dysfunction. PATIENTS, METHODS, AND RESULTS: In four unrelated families, we identified index patients with MHBD deficiency, which implied a diagnosis of HSD10MD. Each index patient was independently investigated because of neurological or developmental concerns. All had persistent elevations of urinary 2-methyl-3-hydroxybutyric acid and tiglylglycine. Analysis of HSD17B10 identified a single missense variant, c.364C>G, p.Leu122Val, in each case. This rare variant (1/183336 alleles in gnomAD) was previously reported in one Dutch patient and was described as pathogenic. The geographic origins of our families and results of haplotype analysis together provide evidence of a founder effect for this variant in Quebec. Notably, we identified an asymptomatic hemizygous adult male in one family, while a second independent genetic disorder contributed substantially to the clinical phenotypes observed in probands from two other families. CONCLUSION: The phenotype associated with p.Leu122Val in HSD17B10 currently appears to be attenuated and nonprogressive. This report widens the spectrum of phenotypic severity of HSD10MD and contributes to genotype-phenotype correlation. At present, we consider p.Leu122Val a "variant of uncertain significance." Nonetheless, careful follow-up of our patients remains advisable, to assess long-term clinical course and ensure appropriate management. It will also be important to identify other potential patients in our population and to characterize their phenotype.

Correction: A new microdeletion syndrome involving TBC1D24, ATP6V0C, and PDPK1 causes epilepsy, microcephaly, and developmental delay.

The original version of this Article contained an error in the spelling of the author Siddharth Banka, which was incorrectly given as Siddhart Banka. This has now been corrected in both the PDF and HTML versions of the Article.

A new microdeletion syndrome involving TBC1D24, ATP6V0C, and PDPK1 causes epilepsy, microcephaly, and developmental delay.

PURPOSE: Contiguous gene deletions are known to cause several neurodevelopmental syndromes, many of which are caused by recurrent events on chromosome 16. However, chromosomal microarray studies (CMA) still yield copy-number variants (CNVs) of unknown clinical significance. We sought to characterize eight individuals with overlapping 205-kb to 504-kb 16p13.3 microdeletions that are distinct from previously published deletion syndromes. METHODS: Clinical information on the patients and bioinformatic scores for the deleted genes were analyzed. RESULTS: All individuals in our cohort displayed developmental delay, intellectual disability, and various forms of seizures. Six individuals were microcephalic and two had strabismus. The deletion was absent in all 13 parents who were available for testing. The area of overlap encompasses seven genes including TBC1D24, ATP6V0C, and PDPK1 (also known as PDK1). Bi-allelic TBC1D24 pathogenic variants are known to cause nonsyndromic deafness, epileptic disorders, or DOORS syndrome (deafness, onychodystrophy, osteodystrophy, mental retardation, seizures). Sanger sequencing of the nondeleted TBC1D24 allele did not yield any additional pathogenic variants. CONCLUSIONS: We propose that 16p13.3 microdeletions resulting in simultaneous haploinsufficiencies of TBC1D24, ATP6V0C, and PDPK1 cause a novel rare contiguous gene deletion syndrome of microcephaly, developmental delay, intellectual disability, and epilepsy.

Health-Related Quality of Life for Patients With Genetically Determined Leukoencephalopathy.

BACKGROUND: We attempted to characterize the health-related quality of life in patients with genetically determined leukoencephalopathies as it relates to the severity of clinical features and the presence or absence of a precise molecular diagnosis. METHODS: Health-related quality of life was assessed using the Pediatric Quality of Life Inventory model (Pediatric Quality of Life Inventory 4.0 Self- and Proxy-reports) on 59 patients diagnosed with genetically determined leukoencephalopathies. In total, 38 male and 21 female patients ranging from one to 32 years of age (mean nine years), as well as their parents, completed the Pediatric Quality of Life Inventory health-related quality of life measures. In addition, participants completed detailed standardized clinical assessments or questionnaires. The correlation between health-related quality of life results and the severity of the clinical features, as well as the presence or absence of a molecular diagnosis, were analyzed. RESULTS: Patients with more severe clinical features showed statistically significant lower total Pediatric Quality of Life Inventory scores. More specifically, lower health-related quality of life was noted in children with sialorrhea, gastrostomy, and dystonia and in children who use a wheelchair. CONCLUSIONS: Patients with more severe clinical features experience a lower quality of life. Our study further highlights the importance of addressing both physical and psychosocial issues and discussing perception of quality of life with both parents and children. A larger multicenter prospective study will be needed to further define the burden of these diseases and to identify modifiable factors.

Joubert Syndrome in French Canadians and Identification of Mutations in CEP104.

Joubert syndrome (JBTS) is a primarily autosomal-recessive disorder characterized by a distinctive mid-hindbrain and cerebellar malformation, oculomotor apraxia, irregular breathing, developmental delay, and ataxia. JBTS is a genetically heterogeneous ciliopathy. We sought to characterize the genetic landscape associated with JBTS in the French Canadian (FC) population. We studied 43 FC JBTS subjects from 35 families by combining targeted and exome sequencing. We identified pathogenic (n = 32 families) or possibly pathogenic (n = 2 families) variants in genes previously associated with JBTS in all of these subjects, except for one. In the latter case, we found a homozygous splice-site mutation (c.735+2T>C) in CEP104. Interestingly, we identified two additional non-FC JBTS subjects with mutations in CEP104; one of these subjects harbors a maternally inherited nonsense mutation (c.496C>T [p.Arg166*]) and a de novo splice-site mutation (c.2572-2A>G), whereas the other bears a homozygous frameshift mutation (c.1328_1329insT [p.Tyr444fs*3]) in CEP104. Previous studies have shown that CEP104 moves from the mother centriole to the tip of the primary cilium during ciliogenesis. Knockdown of CEP104 in retinal pigment epithelial (RPE1) cells resulted in severe defects in ciliogenesis. These observations suggest that CEP104 acts early during cilia formation by regulating the conversion of the mother centriole into the cilia basal body. We conclude that disruption of CEP104 causes JBTS. Our study also reveals that the cause of JBTS has been elucidated in the great majority of our FC subjects (33/35 [94%] families), even though JBTS shows substantial locus and allelic heterogeneity in this population.

Genetically proven cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) in a 3-year-old.

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) has always been considered to be a middle-age-onset disease. Diagnosis is confirmed by genetic testing and the finding of the Notch3 mutation or by skin biopsy. Imaging plays a pivotal and crucial role in confirming this diagnosis by identifying white matter changes early in the disease. This can be useful in screening symptomatic patients with a family history of the disease. CADASIL cases have been reported recently in children. We report our experience with CADASIL in a 3-year-old boy.

Risk of Guillain-Barré syndrome following H1N1 influenza vaccination in Quebec.

CONTEXT: In fall 2009 in Quebec, Canada, an immunization campaign was launched against the 2009 influenza A(H1N1) pandemic strain, mostly using an AS03 adjuvant vaccine. By the end of the year, 57% of the 7.8 million residents had been vaccinated. OBJECTIVE: To assess the risk of Guillain-Barré syndrome (GBS) following pandemic influenza vaccine administration. DESIGN: Population-based cohort study with follow-up over the 6-month period October 2009 through March 2010. The investigation was ordered by the chief medical officer of health in accordance with the Quebec Public Health Act. SETTING: All acute care hospitals and neurology clinics in Quebec. POPULATION: Suspected and confirmed GBS cases reported by physicians, mostly neurologists, during active surveillance or identified in the provincial hospital summary discharge database. Medical records were reviewed and cases classified according to Brighton Collaboration definitions (categorized as level 1, 2, or 3, corresponding to criteria of decreasing certainty in diagnosis). Immunization status was verified and denominators were estimated from the provincial immunization registry (4.4 million vaccinated) and census data (total target population aged ≥6 months, 7.8 million), with a total of 3,623,046 person-years of observation. MAIN OUTCOME MEASURES: Relative and attributable risks were calculated using a Poisson model and the self-controlled case-series method. RESULTS: Over a 6-month period, 83 confirmed GBS cases were identified, including 71 Brighton level 1 through 3 cases. Twenty-five confirmed cases had been vaccinated against 2009 influenza A(H1N1) 8 or fewer weeks before disease onset, with most (19/25) vaccinated 4 or fewer weeks before onset. In the Poisson model, the age- and sex-adjusted relative risk was 1.80 (95% CI, 1.12-2.87) for all confirmed cases during the 8-week postvaccination period and was 2.75 (95% CI, 1.63-4.62) during the 4-week postvaccination period. Using the self-controlled case-series method, relative risk estimates during the 4-week postvaccination period were 3.02 (95% CI, 1.64-5.56) for all confirmed cases (n = 42) and 2.33 (95% CI, 1.19-4.57) for Brighton level 1 through 3 cases (n = 36). The number of GBS cases attributable to vaccination was approximately 2 per 1 million doses. There was no indication of an excess risk in persons younger than 50 years. CONCLUSIONS: In Quebec, the 2009 influenza A(H1N1) vaccine was associated with a small but significant risk of GBS. It is likely that the benefits of immunization outweigh the risks.

Sanfilippo syndrome type C: mutation spectrum in the heparan sulfate acetyl-CoA: alpha-glucosaminide N-acetyltransferase (HGSNAT) gene.

Mucopolysaccharidosis (MPS) type IIIC or Sanfilippo syndrome type C is a rare autosomal recessive disorder caused by the deficiency of the lysosomal membrane enzyme, heparan sulfate acetyl-CoA (AcCoA): alpha-glucosaminide N-acetyltransferase (HGSNAT; EC 2.3.1.78), which catalyzes transmembrane acetylation of the terminal glucosamine residues of heparan sulfate prior to their hydrolysis by alpha-N-acetylglucosaminidase. Lysosomal storage of undegraded heparan sulfate in the cells of affected patients leads to neuronal death, causing neurodegeneration and severely impaired development accompanied by mild visceral and skeletal abnormalities, including mild dwarfism, coarse facies, and joint stiffness. To date, 50 HGSNAT mutations have been identified in MPS IIIC patients: 40 were previously published and 10 novel mutations are reported here. The mutations span the entire structure of the gene and include 13 splice-site mutations, 11 insertions and deletions, 8 nonsense mutations, and 18 missense mutations (http://chromium.liacs.nl/LOVD2/home.php?select_db=HGSNAT). In addition, four polymorphisms result in amino acid changes that do not affect activity of the enzyme. In this work we discuss the spectrum of MPS IIIC mutations, their clinical presentation and distribution within the patient population, and speculate how the mutations may affect the structure and function of HGSNAT.

Epidemiology of Guillain-Barré syndrome in the province of Quebec.

BACKGROUND: In the province of Quebec, a population-based study of Guillain-Barré syndrome (GBS) was conducted at the time of a mass immunization campaign against meningococcal disease, in 2001. METHODS: The study population included residents aged 2 months to 20 years observed from November 1st, 2000 to December 31, 2002, representing 4,075,465 person-years of observation. GBS cases were identified in the provincial hospital database Med-Echo and medical records were reviewed. RESULTS: Thirty-three incident GBS cases were identified, including 27 cases of acute inflammatory demyelinating polyradiculopathy. The overall GBS incidence rate was 0.8/100,000 person-years, higher in persons aged 1 to 4 years (2.1/100,000) than in those 5 years or more (0.6/100,000). There was a female preponderance and no significant seasonal variation. All patients survived. CONCLUSION: Results could be used to interpret reports of adverse events associated with the introduction of new vaccines in this age-group in Canada.

Risk of Guillain-Barré syndrome following serogroup C meningococcal conjugate vaccine in Quebec, Canada.

To assess the risk of Guillain-Barré syndrome (GBS) following administration of meningococcal serogroup C-CRM(197) conjugate vaccine, provincial immunization records were linked with hospital discharge records, and medical charts were reviewed. In the cohort of 1.9 million individuals (age, 2 months to 20 years), observed postvaccination frequencies of GBS were not higher than expected.