To the Editor—I read the article by Hon et al1 with interest. Although the seasonality of respiratory syncytial virus (RSV) is mostly year-round in tropical and subtropical regions, this should not be a barrier to universal maternal RSV vaccination.2 This approach could work well in Hong Kong, as unlike the monoclonals, the RSV vaccine’s effects are designed to be longer-lasting, and all pregnant women are eligible. In contrast to its much more restricted predecessor, palivizumab, nirsevimab has fewer limitations and can be given to all newborns, providing protection against RSV for up to 5 months after a single dose. Due to its more limited duration of protection, the recommendation is for it to be administered just before the onset of the RSV season (eg, during September/October to March in the Northern Hemisphere).2 3 Nirsevimab can still be given to particularly vulnerable babies following maternal vaccination, especially when vaccination occurs within 14 days of delivery since the maternal vaccine response can take up to 2 weeks to develop.3 In addition, the United States Centers for Disease Control and Prevention recommends that non-vulnerable babies above 8 months of age should not receive nirsevimab, and it is not recommended for any baby over 20 months.3 Nonetheless, the optimal scheduling, combination and effectiveness of these two interventions (RSV vaccines vs monoclonals) clearly require further experience. In the meantime, recommendations from different countries can be confusing, and the local teams in Hong Kong may find it useful to wait a little longer before developing their own local guidelines. Therefore, I agree with the authors that no new practice recommendations should be made at this time regarding RSV vaccines or the long-acting monoclonal nirsevimab.

The author solely contributed to the letter and critical revision of the letter for important intellectual content. The author had full access to the data, contributed to the study, approved the final version for publication, and takes responsibility for its accuracy and integrity.

The author has disclosed no conflicts of interest.

This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Hon KL, Cheung EW, Li AM, et al. Practice recommendations for respiratory syncytial virus prophylaxis among children in Hong Kong. Hong Kong Med J 2025;31:48-57. Crossref

2. Benzaken TR, Watson C, Drysdale SB. Prevention of respiratory syncytial virus disease by immunisation. Arch Dis Child Educ Pract Ed 2024:edpract-2024-326964. Crossref

3. United States Centers for Disease Control and Prevention. RSV Immunization Guidance for Infants and Young Children. 30 Aug 2024. Available from: https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/infants-young-children.html. Accessed 25 Feb 2025.

To the Editor—Chen et al’s article1 in the Hong Kong Medical Journal, “Enhancing human papillomavirus vaccine acceptance in Hong Kong: a call for action and public education,” underscores the pressing need to enhance human papillomavirus (HPV) vaccine acceptance. We propose a multifaceted strategy to bolster parental support for HPV vaccination among schoolchildren in Hong Kong. First, we suggest the creation of accessible, scientifically backed educational material that clearly outlines the benefits and safety profile of HPV vaccines, addressing common misconceptions and knowledge gaps.2 These materials should be easily understood by parents with varying levels of health literacy. Second, employing Fischhoff’s risk perception framework can provide a structured approach to communicate the risks associated with HPV and the protective benefits of vaccination, both vital in reducing vaccine hesitancy.3 4 This framework can help parents make more informed decisions regarding their children’s health. Third, advocating for policy reforms that underscore the importance of HPV vaccines for both genders is essential. These reforms should emphasise the broader implications of HPV-related cancers and the role of vaccination in cancer prevention.5 This approach can help eliminate gender biases and ensure that all children receive the protection they need. Strengthening the communication skills of healthcare providers is another critical area. Training programmes can equip providers with the tools to effectively discuss the necessity and safety of HPV vaccines, thereby alleviating parental concerns and fostering trust.6 Lastly, fostering cross-sectoral collaborations to integrate HPV vaccine education into school health programmes can significantly enhance community health literacy and awareness.7 By leveraging schools as platforms for health education, we can reach a wider audience and instil the importance of HPV vaccination from a young age. These strategic initiatives, underpinned by scientific evidence and community engagement, are essential steps towards significantly increasing HPV vaccine acceptance and compliance in Hong Kong.

Concept or design: J Ke.
Critical revision of the manuscript for important intellectual content: D Zhu.

Both authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

Both authors have disclosed no conflicts of interest.

This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Chen Z, Chan JY, Chan PK. Enhancing human papillomavirus vaccine acceptance in Hong Kong: a call for action and public education. Hong Kong Med J 2024;30:352-4. Crossref

2. Chu JK, Sing CW, Li Y, Wong PH, So EY, Wong IC. Factors affecting human papillomavirus vaccine acceptance among parents of Primary 4 to 6 boys and girls in Hong Kong. Hong Kong Med J 2024;30:386-99. Crossref

3. Thomas RK. Contemporary approaches to health communication. In: Health Communication. New York [NY]: Springer; 2006: 133-47.

4. Fischhoff B, Bostrom A, Quadrel MJ. Risk perception and communication. Annu Rev Public Health 1993;14:183-203. Crossref

5. Drolet M, Bénard É, Pérez N, Brisson M; HPV Vaccination Impact Study Group. Population-level impact and herd effects following the introduction of human papillomavirus vaccination programmes: updated systematic review and meta-analysis. Lancet 2019;394:497-509. Crossref

6. Gilkey MB, Calo WA, Moss JL, Shah PD, Marciniak MW, Brewer NT. Provider communication and HPV vaccination: the impact of recommendation quality. Vaccine 2016;34:1187-92. Crossref

7. Rolland Y, de Souto Barreto P, Abellan Van Kan G, et al. Vitamin D supplementation in older adults: searching for specific guidelines in nursing homes. J Nutr Health Aging 2013;17:402-12. Crossref

To the Editor—We write in response to an article that highlighted the experience of two Cantopop artists whose son was diagnosed with a rare disease.1 Because of its complexity, immediate discussion is warranted of the critical aspects of managing rare diseases in Hong Kong.

Rare disease, which impacts about 300 million individuals globally, encompasses a number of medical conditions across different specialties.2 Neurological disorders and metabolic causes account for 40% and 10% of rare diseases, respectively, with tuberous sclerosis and spinocerebellar ataxia being examples in Hong Kong.3 In general, there is a lack of awareness about rare diseases among healthcare professionals and the public, with consequent delayed diagnosis and treatment.3 Families who cope with diseases often encounter emotional and psychological problems that are compounded by a lack of specialised psychosocial support and palliative care access.4 Moreover, the financial strain of managing diseases is substantial; drug costs for rare diseases are reportedly up to 13.8 times higher than those of more common ailments.3 It is crucial to provide comprehensive care for rare disease patients and their families.

The healthcare system for rare diseases in Hong Kong is not as advanced or well equipped as comparable centres in the US2 and Mainland China.5 It faces challenges at different levels. Key issues include insufficient patient support, absence of a specific registry, limited availability of genetic testing, and a high financial burden for patients. To bridge these gaps, Hong Kong could learn from the well-established networks and care models of the US,2 as well as the central registry in Mainland China,5 and adopt supportive policies and financial assistance programmes. As a starting point, the Hong Kong Genome Institute (https://hkgp.org/en/) provides a strong platform from which to promote public awareness of rare diseases in Hong Kong. In addition, with the newly established Genetics and Genomics (Medicine) Fellowship of the Hong Kong Academy of Medicine,6 genetic testing and counselling that target rare disease could be streamlined.

All authors contributed to the letter and critical revision of the letter for important intellectual content. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

The authors have disclosed no conflicts of interest.

This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Cheng L. Hong Kong star couple Stephanie Ho, Fred Cheng share story of son’s Angelman syndrome diagnosis to raise public awareness. South China Morning Post. 2024 Jun 2: Health & Environment. Available from: https://www.scmp.com/news/hong-kong/health-environment/article/3265045/hong-kong-star-couple-stephanie-ho-fred-cheng-share-story-sons-angelman-syndrome-diagnosis-raise. Accessed 17 Feb 2025.

2. Baynam G, Hartman AL, Letinturier MC, et al. Global health for rare diseases through primary care. Lancet Glob Health 2024;12:e1192-9. Crossref

3. Chung CC, Ng NY, Ng YN, et al. Socio-economic costs of rare diseases and the risk of financial hardship: a cross-sectional study. Lancet Reg Health West Pac 2023;34:100711. Crossref

4. Chan KY, Yap DY, Singh Harry Gill H. Rethinking palliative care in psychiatry. JAMA Psychiatry 2023;80:1089-90. Crossref

5. Guo J, Liu P, Chen L, et al. National Rare Diseases Registry System (NRDRS): China’s first nation-wide rare diseases demographic analyses. Orphanet J Rare Dis 2021;16:515. Crossref

6. Hong Kong Academy of Medicine. Specialty descriptions. 2024 Feb 6. Available from: https://www.hkam.org.hk/sites/default/files/PDFs/2024/SPECRE25%20(Specialty%20descriptions%20-20240206).pdf?v=1736316996530. Accessed 6 Feb 2025.

To the Editor—Ketamine analogues are new psychoactive substances that share the arylcyclohexylamine backbone of ketamine and produce dissociative effects through antagonistic activity at the N-methyl-D-aspartate receptor.1 Ketamine and its analogues have plagued Hong Kong over the last two decades. Our laboratory has identified outbreaks of multiple ketamine analogues in Hong Kong, including 2-oxo-phenylcyclohexylethylamine in 2017,2 2-fluorodeschloroketamine (2F-DCK) and deschloroketamine in 2019,3 and tiletamine in 2019 to 2022 (according to data on file in the Hospital Authority Toxicology Reference Laboratory).

We report identification of a new ketamine analogue, fluoro-2-oxo-phenylcyclohexylethylamine, also known as fluorexetamine (FXE). Recreational use of FXE was first reported in 2018.4 Our laboratory has detected increasing use of FXE in Hong Kong since mid-2023, with FXE now identified in urine samples of 14 patients. Detection of FXE can be difficult since it does not cross-react with bedside ketamine immunoassay and shares common metabolites with 2F-DCK. This may lead to misidentification of FXE metabolites as 2F-DCK metabolites on routine toxicology testing. Clinically, FXE appears to possess similar toxicity to ketamine and 2F-DCK and co-ingestion with other recreational drugs is common, often complicating the clinical presentation.

Effective prevention of the emergence of new psychoactive substances can be achieved through prompt communication and accurate toxicology testing. This approach has been successful in halting the upward trajectory of various ketamine analogues. When encountering patients with clinical features of ketamine abuse but negative immunoassay or urine toxicology results, clinicians are encouraged to submit urine specimens to our laboratory for further testing.

Concept or design: All authors.
Acquisition of data: All authors.
Analysis or interpretation of data: All authors.
Drafting of the manuscript: TM Han, YK Chong.
Critical revision of the manuscript for important intellectual content: All authors.

All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

All authors have disclosed no conflicts of interest.

This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Morris H, Wallach J. From PCP to MXE: a comprehensive review of the non-medical use of dissociative drugs. Drug Test Anal 2014;6:614-32. Crossref

2. Chong YK, Tang MH, Chan CL, Li YK, Ching CK, Mak TW. 2-oxo-PCE: ketamine analogue on the streets. Hong Kong Med J 2017;23:665-6. Crossref

3. Li C, Lai CK, Tang MH, Chan CC, Chong YK, Mak TW. Ketamine analogues multiplying in Hong Kong. Hong Kong Med J 2019;25:169. Crossref

4. National Drug Early Warning System. Alert from the NDEWS Web Monitoring Team: online mentions of fluorexetamine. 2022. Available from: https://ndews.org/wordpress/files/2023/04/8.12.22.pdf. Accessed 12 Jul 2024.

To the Editor—Chan et al1 drew our attention to the fact that tuberculosis can be a great mimicker of other conditions when it affects the knee. Conversely the knee may be a site where problems may mimic other disorders. Knee injuries are among the most common disabling conditions that arise from sporting and other accidents or falls. The presence of septic arthritis may overlap or complicate a traumatic knee condition. Septic arthritis by itself may affect the knee, as well as autoimmune-related arthritis. Yet uncommonly, gout and other crystal arthritis may have a similar clinical and radiological presentation.2 Only when urate or calcium pyrophosphate are identified can the diagnosis be confirmed. The title ‘great mimicker’ was originally applied to syphilis, a disease that declined considerably in the last century but that is recently exhibiting a resurgence due to uncontrolled sexually transmitted diseases.3 Syphilis targets virtually every organ and the knee is no exception. In North America, another spirochete infection, Lyme disease, is known to infect people bitten by ticks or in contact with wild animals, and prominent among its symptoms is arthritis, including that of the knee.4 In Hong Kong, we do not have Lyme disease but we should maintain a high index of suspicion in individuals who have visited North America and who present with fever, fatigue and joint pain. The risk is not confined to recent exposures since the disease may be quiescent for months or even years before a flare-up.

The author solely contributed to the concept or design, acquisition of data, analysis or interpretation of data, drafting of the letter, and critical revision of the letter for important intellectual content. The author had full access to the data, contributed to the study, approved the final version for publication, and takes responsibility for its accuracy and integrity.

The author has disclosed no conflict of interest.

This letter received no specific grant from any funding agency in the public, commercial, or not-for profit sectors.

1. Chan HM, Fu H, Chiu KY. Tuberculosis of the knee as a great mimicker of inflammatory arthritis: a case report. Hong Kong Med J 2023;29:548-50. Crossref

2. Yun SY, Choo HJ, Jeong HW, Lee SJ. Comparison of MR findings between patients with septic arthritis and acute gouty arthritis of the knee. J Korean Soc Radiol 2022;83:1071-80. Crossref

3. Peeling RW, Hook EW 3rd. The pathogenesis of syphilis: the great mimicker, revisited. J Pathol 2006;208:224-32. Crossref

4. Arvikar SL, Steere AC. Diagnosis and treatment of Lyme arthritis. Infect Dis Clin North Am 2015;29:269-80. Crossref