Mitochondrial diseases in Hong Kong: prevalence, clinical characteristics and genetic landscape.

OBJECTIVE: To determine the prevalence of mitochondrial diseases (MD) in Hong Kong (HK) and to evaluate the clinical characteristics and genetic landscape of MD patients in the region. METHODS: This study retrospectively reviewed the phenotypic and molecular characteristics of MD patients from participating public hospitals in HK between January 1985 to October 2020. Molecularly and/or enzymatically confirmed MD cases of any age were recruited via the Clinical Analysis and Reporting System (CDARS) using relevant keywords and/or International Classification of Disease (ICD) codes under the HK Hospital Authority or through the personal recollection of treating clinicians among the investigators. RESULTS: A total of 119 MD patients were recruited and analyzed in the study. The point prevalence of MD in HK was 1.02 in 100,000 people (95% confidence interval 0.81-1.28 in 100,000). 110 patients had molecularly proven MD and the other nine were diagnosed by OXPHOS enzymology analysis or mitochondrial DNA depletion analysis with unknown molecular basis. Pathogenic variants in the mitochondrial genome (72 patients) were more prevalent than those in the nuclear genome (38 patients) in our cohort. The most commonly involved organ system at disease onset was the neurological system, in which developmental delay, seizures or epilepsy, and stroke-like episodes were the most frequently reported presentations. The mortality rate in our cohort was 37%. CONCLUSION: This study is a territory-wide overview of the clinical and genetic characteristics of MD patients in a Chinese population, providing the first available prevalence rate of MD in Hong Kong. The findings of this study aim to facilitate future in-depth evaluation of MD and lay the foundation to establish a local MD registry.

Guillain-Barré syndrome in children - High occurrence of Miller Fisher syndrome in East Asian region.

BACKGROUND: Guillain-Barré syndrome (GBS) is a rare acquired immune-mediated polyneuropathy. Updated population-based data concerning paediatric GBS is needed. METHODS: Paediatric patients aged below 18 years diagnosed with GBS between 2009 and 2018 in all 11 paediatric departments in Hong Kong were identified from the Hong Kong Hospital Authority Clinical Data Analysis and Reporting System. The collected data from medical health records were reviewed by paediatric neurologist from each department. Estimated incidence of paediatric GBS was calculated. We also compared our findings with other paediatric GBS studies in Asia. RESULTS: 63 subjects of paediatric GBS were identified, giving an estimated annual incidence of 0.62 per 100,000 population. Half of the subjects had acute inflammatory demyelinating polyneuropathy (AIDP) (n = 31; 49.2%), one quarter had Miller Fisher Syndrome (MFS) (n = 16; 25.4%), one-fifth had axonal types of GBS (n = 12; 19.0%), and four were unclassified. Paediatric subjects with axonal subtypes of GBS compared to the other 2 subtypes, had significantly higher intensive care unit (ICU) admission rates (p = 0.001) and longest length of stay (p = 0.009). With immunomodulating therapy, complete recovery was highest in those with MFS (100%), followed by AIDP (87.1%) and axonal GBS (75%). Our study also confirms a higher MFS rate for paediatric GBS in East Asia region and our study has the highest MFS rate (25.4%). CONCLUSION: Our population-based 10-year paediatric GBS study provides updated evidence on estimated incidence, healthcare burden and motor outcome of each subtype of paediatric GBS and confirmed a higher occurrence of paediatric MFS in East Asia.

Exome sequencing in paediatric patients with movement disorders.

BACKGROUND: Movement disorders are a group of heterogeneous neurological diseases including hyperkinetic disorders with unwanted excess movements and hypokinetic disorders with reduction in the degree of movements. The objective of our study is to investigate the genetic etiology of a cohort of paediatric patients with movement disorders by whole exome sequencing and to review the potential treatment implications after a genetic diagnosis. RESULTS: We studied a cohort of 31 patients who have paediatric-onset movement disorders with unrevealing etiologies. Whole exome sequencing was performed and rare variants were interrogated for pathogenicity. Genetic diagnoses have been confirmed in 10 patients with disease-causing variants in CTNNB1, SPAST, ATP1A3, PURA, SLC2A1, KMT2B, ACTB, GNAO1 and SPG11. 80% (8/10) of patients with genetic diagnosis have potential treatment implications and treatments have been offered to them. One patient with KMT2B dystonia showed clinical improvement with decrease in dystonia after receiving globus pallidus interna deep brain stimulation. CONCLUSIONS: A diagnostic yield of 32% (10/31) was reported in our cohort and this allows a better prediction of prognosis and contributes to a more effective clinical management. The study highlights the potential of implementing precision medicine in the patients.

Delineation of molecular findings by whole-exome sequencing for suspected cases of paediatric-onset mitochondrial diseases in the Southern Chinese population.

BACKGROUND: Mitochondrial diseases (MDs) are a group of clinically and genetically heterogeneous disorders characterized by defects in oxidative phosphorylation. Since clinical phenotypes of MDs may be non-specific, genetic diagnosis is crucial for guiding disease management. In the current study, whole-exome sequencing (WES) was performed for our paediatric-onset MD cohort of a Southern Chinese origin, with the aim of identifying key disease-causing variants in the Chinese patients with MDs. METHODS: We recruited Chinese patients who had paediatric-onset MDs and a minimum mitochondrial disease criteria (MDC) score of 3. Patients with positive target gene or mitochondrial DNA sequencing results were excluded. WES was performed, variants with population frequency ≤ 1% were analysed for pathogenicity on the basis of the American College of Medical Genetics and Genomics guidelines. RESULTS: Sixty-six patients with pre-biopsy MDC scores of 3-8 were recruited. The overall diagnostic yield was 35% (23/66). Eleven patients (17%) were found to have mutations in MD-related genes, with COQ4 having the highest mutation rate owing to the Chinese-specific founder mutation (4/66, 6%). Twelve patients (12/66, 18%) had mutations in non-MD-related genes: ATP1A3 (n = 3, two were siblings), ALDH5A1, ARX, FA2H, KCNT1, LDHD, NEFL, NKX2-2, TBCK, and WAC. CONCLUSIONS: We confirmed that the COQ4:c.370G>A, p.(Gly124Ser) variant, was a founder mutation among the Southern Chinese population. Screening for this mutation should therefore be considered while diagnosing Chinese patients suspected to have MDs. Furthermore, WES has proven to be useful in detecting variants in patients suspected to have MDs because it helps to obtain an unbiased and precise genetic diagnosis for these diseases, which are genetically heterogeneous.

Presentation and Outcome of Acute Necrotizing Encephalopathy of Childhood: A 10-Year Single-Center Retrospective Study From Hong Kong.

Acute necrotizing encephalopathy (ANE) is a rare disease in childhood. We reviewed the 10-year data from a local pediatric department, reported the clinical characteristics, laboratory tests, neuroimaging findings, and outcome of the acute necrotizing encephalopathy cases and identified the potential factors affecting the outcome. Eight episodes of acute necrotizing encephalopathy among 7 patients were recorded, in which all of them had an initial presentation of fever and seizure. We identified that acute necrotizing encephalopathy patients with a severe score of Glasgow Coma Scale (GCS) on presentation, brainstem involvement in magnetic resonance imaging (MRI) of the brain, and higher MR imaging scores were associated with worse outcome. Association of outcome with acute necrotizing encephalopathy severity score, platelet count, and serum alanine aminotransferase level did not reach a statistically significant level. These results highlight the importance of combined clinical, laboratory, and neuroimaging findings in determining the prognostic outcome of acute necrotizing encephalopathy patients.

Prevalence and Characteristics of Chinese Patients With Duchenne and Becker Muscular Dystrophy: A Territory Wide Collaborative Study in Hong Kong.

The aim of this collaborative study on Duchenne muscular dystrophy and Becker muscular dystrophy is to determine the prevalence and to develop data on such patients as a prelude to the development of registry in Hong Kong. Information on clinical and molecular findings, and patient care, was systematically collected in 2011 and 2012 from all Pediatric Neurology Units in Hong Kong. Ninety patients with dystrophinopathy were identified, and 83% has Duchenne muscular dystrophy. The overall prevalence of dystrophinopathy in Hong Kong in 2010 is 1.03 per 10 000 males aged 0 to 24 years. Among the Duchenne group, we observed a higher percentage (40.6%) of point mutations with a lower percentage (45.3%) of exon deletions in our patients when compared with overseas studies. Although we observed similar percentage of Duchenne group received scoliosis surgery, ventilation support, and cardiac treatment when compared with other countries, the percentage (25%) of steroid use is lower.

Norovirus as cause of benign convulsion associated with gastro-enteritis.

AIM: Rotavirus and norovirus gastro-enteritis (GE) are common in children. Complications, except severe dehydration, are rare. Rotavirus was known to cause seizures and even GE encephalopathy, but these complications are less described in norovirus infection. The objective of this study is to compare the demographic features, clinical manifestations including the incidence of afebrile seizure, and the outcomes in children with rotavirus and norovirus infections. METHODS: This is a retrospective review of children between age 1 month and 6 years admitted to the paediatric department of a regional hospital in Hong Kong with rotavirus and norovirus infections over a period of 3 years from 1 June 2006 to 31 May 2009. Their demographic data, clinical features, laboratory results and outcomes were compared and analysed. RESULTS: Two hundred and thirty-two children with rotavirus and 173 children with norovirus GE were admitted within the study period. Afebrile seizure commonly occurred in norovirus infection (8.67% vs. 1.29%, P < 0.001). Children with rotavirus infection had higher temperature and more diarrhoea episodes, while more blood-stained stool was noted in the norovirus group. Rotavirus-infected patients stayed longer in hospital. All of them had full recovery without any complication. Among the 18 patients who developed afebrile convulsions, 17 of them had neuroimaging performed, which was normal. Fourteen of them had electroencephalogram (EEG) performed, demonstrating normal or non-specific findings. None of them developed subsequent seizure attack after the GE episode. CONCLUSIONS: Norovirus is more commonly associated with benign convulsion in GE than rotavirus. We need to identify the presence of virus, in particular norovirus, in children with GE and afebrile generalised tonic-clonic seizure. Further neuro-investigations may not be necessary once the aetiology is established. Prognosis is excellent in this group of children and prophylactic anticonvulsant is not needed.