BackgroundThe burden of rare diseases is important for healthcare planning but difficult to estimate. This has been facilitated by the development of ORPHAcodes, a comprehensive classification and coding system for rare diseases developed by the international consortium Orphanet, with cross-references to the 10th version of the International Classification of Diseases and Related Health Problems (ICD-10). A recent study in Western Australia made use of this cross-referencing to identify rare diseases-related admissions in health administrative datasets. Such methodology was adopted in Hong Kong, which has a population of 7 million comprising of 92% ethnic Chinese, with over 80% of admissions taking place in the public hospitals and available for review from the local public healthcare database.Main bodyOur objective was to identify the inpatient healthcare burden of rare diseases in Hong Kong. We extracted admission records of all patients coded with one or more of the 1084 ICD-10 codes cross referenced with 467 ORPHAcodes during the study period from 1st January 2005 to 31st December 2016. We further analysed rare disease-related inpatient healthcare cost using a subset of patients admitted during 1st April 2015 – 31st March 2016. A total number of 546,673 admissions were identified, representing 3.2% of total admissions during the study period. By the end of the study, 109,535 patients were alive, representing 1.5% of the overall population. Prevalence of rare diseases was found to be 1 in 67 in the Hong Kong population. The most common rare disease category in the paediatric age group was ‘rare developmental defect during embryogenesis’; whereas that amongst adults was ‘rare haematologic disease’. The aforementioned subset of patients accounted for 330,091 inpatient-days, placing the estimated total inpatient cost for rare disease population at HKD$1,594,339,530 i.e. 4.3% of total inpatient cost in 2015–2016.ConclusionCross referencing between ICD-10 and ORPHAcodes may be adopted in different healthcare datasets for international comparison. Despite differences in the prevalence of individual disease, the disparity between rare disease prevalence (1.5%) and associated inpatient cost (4.3%) in Hong Kong reflects the importance of rare diseases in healthcare policies.

BackgroundInfluenza is one of the most common causes of acute respiratory tract infections around the world. Influenza viruses can cause seasonal epidemics. There remains limited information on the impact of both seasonal influenza A and influenza B related hospitalisations from neurological complications in paediatric populations in Asia.ObjectivesTo examine both the clinical spectrum and healthcare burden of influenza-associated neurological complications (IANCs) within the paediatric population of Hong Kong.MethodsWe conducted a population-based retrospective study to identify all paediatric patients (<18 years) admitted to a public hospital in Hong Kong with a confirmed influenza A or B infection between 2014 and 2018 using the Clinical Data Analysis and Reporting System of the Hospital Authority. The clinical spectrum of the paediatric patients with IANCs was studied. The clinical burden of paediatric influenza patients with IANCs were compared to paediatric influenza patients without neurological complications.ResultsA total of 28,016 children admitted to the paediatric wards diagnosed to have influenza A or B infection were identified, accounting for 5.7% (28,016/489,955) of total paediatric admissions. 67.3% had influenza A and 32.7% had influenza B, and 8.9% had IANCs. The mean annual incidence of IANCs in children was 57 per 100,000 population. The spectrum of IANCs in our paediatric patients included febrile seizures (80.6%), myositis (11.4%), seizures with fever (5.4%), influenza-associated encephalitis/encephalopathy (IAE) (2.6%) and rarely Guillain–Barré syndrome (0.04%). Most paediatric patients with IANCs (85.5%) presented at a young age of <6 years. Paediatric patients with IANCs had significant longer hospital stays (p < 0.001), higher percentages of mechanical ventilation use (p < 0.05) and PICU admissions (p < 0.001), and higher mortality rates (p < 0.001) compared to those without neurological complications. Amongst those with IANCs, IAE was the sole cause of all seven reported mortalities.ConclusionsSeasonal influenza A & B is a common cause of hospitalisation for paediatric patients in Hong Kong. We found neurological complications from influenza A and B caused a significantly higher clinical burden compared to those without neurological complications. Children in younger age groups (<6 years old) are at highest risk and thus increasing vaccination coverage to this age group is recommended.

BackgroundArray comparative genomic hybridization (aCGH) is recommended as a first-tier genetic test for children with autism spectrum disorder (ASD). However, interpretation of results can often be challenging partly due to the fact that copy number variants (CNVs) in non-European ASD patients are not well studied. To address this literature gap, we report the CNV findings in a cohort of Chinese children with ASD.MethodsDNA samples were obtained from 258 Chinese ASD patients recruited from a child assessment center between January 2011 and August 2014. aCGH was performed using NimbleGen-CGX-135k or Agilent-CGX 60k oligonucleotide array. Results were classified based on existing guidelines and literature.ResultsTen pathogenic CNVs and one likely pathogenic CNV were found in nine patients, with an overall diagnostic yield of 3.5%. A 138 kb duplication involving 3′ exons of DPP10 (arr[GRCh37] 2q14.1(116534689_116672358)x3), reported to be associated with ASD, was identified in one patient (0.39%). The same CNV was reported as variant of uncertain significance (VUS) in DECIPHER database. Multiple individuals of typical development carrying a similar duplication were identified among our ancestry-matched control with a frequency of 6/653 (0.92%) as well as from literature and genomic databases.ConclusionsThe DPP10 duplication is likely a benign CNV polymorphism enriched in Southern Chinese with a population frequency of ~1%. This highlights the importance of using ancestry-matched controls in interpretation of aCGH findings.Electronic supplementary materialThe online version of this article (doi:10.1186/s13229-017-0136-x) contains supplementary material, which is available to authorized users.

De novo germline mutations in HRAS cause Costello syndrome, with >95% of the mutations causing Costello syndrome affecting amino acid position 12 (p.Gly12) or 13 (p.Gly13). We report on a patient with de novo missense mutation causing an amino acid change at codon 146 of HRAS, c.436G > C:p.Ala146Pro, who presented with subtle dysmorphic features, failure to thrive, global developmental delay, and hypertrophic obstructive cardiomyopathy. Mutations affecting codon 146 are observed in <1% of patients with Costello syndrome. From literature search, there were only two other patients reported with mutations involving the same location. We summarized and updated their findings, and discussed evidence to show that these patients with less obvious signs of Costello syndrome may not necessarily run a more benign clinical course.