Collagen VI-related myopathies: clinical variability, phenotype-genotype correlation and exploratory transcriptome study.

Collagen VI-related myopathies are a group of disorders that cause muscle weakness and joint contractures with significant variability in disease severity among patients. Here we report the clinical and genetic characteristics of 13 Chinese patients. Detailed histological, radiological and muscle transcriptomic evaluations were also conducted for selected representative patients. Across the cohort, fifteen putative disease causal variants were identified in three genes encoding collagen VI subunits, COL6A1 (n=6), COL6A2 (n=5), and COL6A3 (n=4). Most of these variants (12/15, 80%) were dominant negative and occurred at the triple helical domain. The rest (3/15, 20%) were located at the C-terminus. Two previously unreported variants, an in-frame mutation (COL6A1:c.1084_1092del) and a missense mutation (COL6A2:c.811G>C), were also noted. The transcriptome data from the muscle biopsies of two patients in the study with dominant negative mutations [COL6A2:c.811G>C and COL6A1:c.930+189C>T] supports the accepted aetiology of Collagen VI myopathy as dysfunction of the extracellular matrix. It also suggests there are perturbations to skeletal muscle differentiation and skeletal system development. It should be noted that although the phenotypes of patients can be mostly explained by the position and dominant-negative effect of the variants, exceptions and variability still exist and have to be reckoned with. This study provides valuable data explaining the varying severity of phenotypes among ethnically Chinese patients.

Neuroimaging in Primary Coenzyme-Q10-Deficiency Disorders.

Coenzyme Q10 (CoQ10) is an endogenously synthesized lipid molecule. It is best known for its role as a cofactor within the mitochondrial respiratory chain where it functions in electron transfer and ATP synthesis. However, there are many other cellular pathways that also depend on the CoQ10 supply (redox homeostasis, ferroptosis and sulfide oxidation). The CoQ10 biosynthesis pathway consists of several enzymes, which are encoded by the nuclear DNA. The majority of these enzymes are responsible for modifications of the CoQ-head group (benzoquinone ring). Only three enzymes (PDSS1, PDSS2 and COQ2) are required for assembly and attachment of the polyisoprenoid side chain. The head-modifying enzymes may assemble into resolvable domains, representing COQ complexes. During the last two decades, numerous inborn errors in CoQ10 biosynthesis enzymes have been identified. Thus far, 11 disease genes are known (PDSS1, PDSS2, COQ2, COQ4, COQ5, COQ6, COQ7, COQ8A, COQ8B, COQ9 and HPDL). Disease onset is highly variable and ranges from the neonatal period to late adulthood. CoQ10 deficiency exerts detrimental effects on the nervous system. Potential consequences are neuronal death, neuroinflammation and cerebral gliosis. Clinical features include encephalopathy, regression, movement disorders, epilepsy and intellectual disability. Brain magnetic resonance imaging (MRI) is the most important tool for diagnostic evaluation of neurological damage in individuals with CoQ10 deficiency. However, due to the rarity of the different gene defects, information on disease manifestations within the central nervous system is scarce. This review aims to provide an overview of brain MRI patterns observed in primary CoQ10 biosynthesis disorders and to highlight disease-specific findings.

Recurrent de novo missense variants in GNB2 can cause syndromic intellectual disability.

PURPOSE: Binding proteins (G-proteins) mediate signalling pathways involved in diverse cellular functions and comprise Gα and Gßγ units. Human diseases have been reported for all five Gß proteins. A de novo missense variant in GNB2 was recently reported in one individual with developmental delay/intellectual disability (DD/ID) and dysmorphism. We aim to confirm GNB2 as a neurodevelopmental disease gene, and elucidate the GNB2-associated neurodevelopmental phenotype in a patient cohort. METHODS: We discovered a GNB2 variant in the index case via exome sequencing and sought individuals with GNB2 variants via international data-sharing initiatives. In silico modelling of the variants was assessed, along with multiple lines of evidence in keeping with American College of Medical Genetics and Genomics guidelines for interpretation of sequence variants. RESULTS: We identified 12 unrelated individuals with five de novo missense variants in GNB2, four of which are recurrent: p.(Ala73Thr), p.(Gly77Arg), p.(Lys89Glu) and p.(Lys89Thr). All individuals have DD/ID with variable dysmorphism and extraneurologic features. The variants are located at the universally conserved shared interface with the Gα subunit, which modelling suggests weaken this interaction. CONCLUSION: Missense variants in GNB2 cause a congenital neurodevelopmental disorder with variable syndromic features, broadening the spectrum of multisystem phenotypes associated with variants in genes encoding G-proteins.

Impact of COVID-19 pandemic on patients with rare disease in Hong Kong.

The COVID-19 pandemic has had significant health, social, and economic consequences internationally. While the pandemic has direct implications on infected patients and families, there is a need to examine the pandemic's effect on patients with non-COVID-19-related diseases. This study examines the impact of the COVID-19 pandemic on 272 rare disease patients with 89 distinct rare diseases in Hong Kong using a cross-sectional online survey between April 10 and April 29, 2020 from the patient and caregiver perspective. The pandemic has impacted patient's health status in 46%, service use patterns in 71%, mental health in 79%, daily living in 82%, social life in 92%, and financial status in 81% of patients. Patient's health status, medical and rehabilitation, and mental health were more impacted by the COVID-19 pandemic in the group of patients with any level of dependency according to the Barthel Index for Activities of Daily Living compared with that in the group of patients who are fully independent (p < 0.0001; p < 0.0001; p = 0.0420). This study is the first study to examine the impact of COVID-19 pandemic on the rare disease population in Hong Kong, and demonstrates the pandemic's effect on service and resource utilization, and patient's physical and mental well-being.

Megaconial congenital muscular dystrophy: Same novel homozygous mutation in CHKB gene in two unrelated Chinese patients.

Megaconial congenital muscular dystrophy (CMD) is a rare form of congenital muscular dystrophy attributed to an autosomal recessive CHKB mutation. We report two unrelated Chinese girls with Megaconial CMD who harbored the same novel homozygous CHKB mutation but exhibited different phenotypes. Patient 1, who is now 8 years old, has autism, intellectual disabilities, mild girdle weakness, and characteristic muscle biopsy with COX-negative fibers. Patient 2, now 12 years old, has limited intelligence and marked weakness, with scoliosis, hip subluxation and early loss of ambulation. Both exhibited mildly elevated creatine kinase levels, have relative sparing of adductor longus and extensor digitorum longus on MRI leg muscles, and a c.598del (p.Gln200Argfs*11) homozygous CHKB loss-of-function mutation. Their parents are heterozygous carriers. This is the first report of Megaconial CMD in Chinese patients demonstrating the pathogenicity of the identified homozygous CHKB variant. A case review of all previously reported patients of different ethnicities is also included.

A fatal case of COQ7-associated primary coenzyme Q10 deficiency.

BACKGROUND: Primary coenzyme Q10 (CoQ10) deficiencies are clinically and genetically heterogeneous group of disorders associated with defects of genes involved in the CoQ10 biosynthesis pathway. COQ7-associated CoQ10 deficiency is very rare and only two cases have been reported. METHODS AND RESULTS: We report a patient with encephalo-myo-nephro-cardiopathy, persistent lactic acidosis, and basal ganglia lesions resulting in early infantile death. Using whole exome sequencing, we identified compound heterozygous variants in the COQ7 gene consisting of a deletion insertion resulting in frameshift [c.599_600delinsTAATGCATC, p.(Lys200Ilefs*56)] and a missense substitution [c.319C>T, p.(Arg107Trp), NM_016138.4]. Skin fibroblast studies showed decreased combined complex II + III activity and reduction in CoQ10 level. CONCLUSION: This third patient presenting with lethal encephalo-myo-nephro-cardiopathy represents the severe end of this ultra-rare mitochondrial disease caused by biallelic COQ7 mutations. The response to CoQ10 supplement is poor and alternative treatment strategies should be developed for a more effective management of this disorder.

The different facets of "culture" in genetic counseling: A situated analysis of genetic counseling in Hong Kong.

In this article, we problematize the concept of "culture" in genetic counseling. With globalization and increased mobility of both genetic professionals and clients, there is an increased acknowledgement of the impact of "culture" on a counseling process. There is, however, little agreement on what "culture" is. The essentialist understanding that has long been dominant in the medical literature views culture as a set of shared beliefs, attitudes and practices among a group of people. Such an approach does not account for the individual differences and the dynamic nature of genetic counseling encounters. Following Zayts and Schnurr (2017), we use the distinction between two orders of culture: culture1 that refers to the static, generalized understanding of culture that is external to the specific context, and culture2 , an analytic concept that denotes dynamic enactments of culture, emerging in the interaction. We use empirical data from genetic counseling sessions to illustrate these different facets of culture and to consider how and why speakers draw on them. The clinical implications of the study include highlighting the importance of cultural awareness among counselors, including cultural self-awareness, and demonstrating how authentic interactional data could be used to enhance cultural training in genetic counseling.

Exome sequencing for paediatric-onset diseases: impact of the extensive involvement of medical geneticists in the diagnostic odyssey.

Currently, offering whole-exome sequencing (WES) via collaboration with an external laboratory is increasingly common. However, the receipt of a WES report can be merely the beginning of a continuing exploration process rather than the end of the diagnostic odyssey. The laboratory often does not have the information the physician has, and any discrepancies in variant interpretation must be addressed by a medical geneticist. In this study, we performed diagnostic WES of 104 patients with paediatric-onset genetic diseases. The post-exome review of WES reports by the clinical geneticist led to a more comprehensive assessment of variant pathogenicity in 16 cases. The overall diagnostic yield was 41% (n = 43). Among these 43 diagnoses, 51% (22/43) of the pathogenic variants were nucleotide changes that have not been previously reported. The time required for the post-exome review of the WES reports varied, and 26% (n = 27) of the reports required an extensive amount of time (>3 h) for the geneticist to review. In this predominantly Chinese cohort, we highlight the importance of discrepancies between global and ethnic-specific frequencies of a genetic variant that complicate variant interpretation and the significance of post-exome diagnostic modalities in genetic diagnosis using WES. The challenges faced by geneticists in interpreting WES reports are also discussed.

A simple blood test expedites the diagnosis of glucose transporter type 1 deficiency syndrome.

Glucose transporter type 1 (GLUT1) deficiency syndrome (GLUT1-DS) leads to a wide range of neurological symptoms. Ketogenic diets are very efficient to control epilepsy and movement disorders. We tested a novel simple and rapid blood test in 30 patients with GLUT1-DS with predominant movement disorders, 18 patients with movement disorders attributed to other genetic defects, and 346 healthy controls. We detected significantly reduced GLUT1 expression only on red blood cells from patients with GLUT1-DS (23 patients; 78%), including patients with inconclusive genetic analysis. This test opens perspectives for the screening of GLUT1-DS in children and adults with cognitive impairment, movement disorder, or epilepsy. Ann Neurol 2017;82:133-138.