Orphanet Journal of Rare Diseases | Challenges and opportunities of genetic testing and counseling for mucopolysaccharidosis type II in Kenya

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This study systematically analyzed the genotype-phenotype correlations of mucopolysaccharidosis type II (MPS II) in the Kenyan population for the first time, revealing diagnostic delays and sociocultural barriers in low-income countries, and providing important references for future development of newborn screening and genetic services in African populations.

 

Literature Overview
This article, titled 'Challenges and opportunities with providing genetic testing and counseling for mucopolysaccharidosis type II in Kenya', published in the Orphanet Journal of Rare Diseases, reviews and summarizes the challenges and opportunities associated with providing genetic testing and counseling for mucopolysaccharidosis type II (MPS II) in Kenya. The article points out that low-income countries like Kenya face significant resource gaps in the diagnosis and management of genetic disorders, leading patients to miss the golden window for early intervention. It also reveals that sociocultural factors affect the acceptance of genetic testing, such as stigmatization of mothers whose children are affected. Additionally, it emphasizes the necessity of establishing localized, low-cost genetic screening platforms.

Background Knowledge
Mucopolysaccharidosis type II (MPS II) is an X-linked recessive disorder caused by mutations in the IDS gene, leading to deficiency of the iduronate-2-sulfatase (I2S) enzyme and subsequent accumulation of glycosaminoglycans (GAGs) in tissues. The disease is categorized into neuronopathic and non-neuronopathic forms, with the former being more severe and rapidly progressive. Globally, over 600 IDS gene mutations have been reported, and certain correlations exist between mutation types and disease severity. In high-income countries, early diagnosis and enzyme replacement therapy (ERT) interventions can be achieved through newborn screening, enzyme activity testing, and gene sequencing, significantly improving patient prognosis. However, in low-income countries such as Kenya, most patients are diagnosed at an advanced stage or even abandon treatment due to misdiagnosis or social stigma, owing to the lack of professional genetic counselors, genetic testing resources, and public awareness of genetics. Furthermore, cultural taboos prevent some families from discussing the medical history of deceased members, which hinders pedigree analysis and risk assessment. Therefore, this study focuses on the genetic mutation characteristics of Kenyan MPS II patients, exploring the applicability of genetic testing in African populations and sociocultural barriers, aiming to provide empirical support for the future establishment of newborn screening and development of genetic service guidelines.

 

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Research Methods and Experiments
The research team recruited 60 participants from 13 families at the endocrinology clinic of Kenyatta National Hospital in Nairobi, Kenya. The participants included 25 male individuals suspected of having MPS II and 35 female relatives. After obtaining informed consent and providing genetic counseling, blood samples were collected via dried blood spots (DBS) and sent to overseas laboratories for targeted gene sequencing (CentoMetabolic panel) and enzyme activity analysis. Researchers performed genotype and phenotype classification and correlation analysis, assessed the proportion of female carriers, and analyzed male mortality within the pedigrees.

Key Findings and Perspectives

• Among the 25 male participants, 17 were found to carry pathogenic or likely pathogenic variants, with 11 presenting severe phenotypes and 6 mild phenotypes. Severe phenotypes were mostly associated with frameshift, nonsense, or splice mutations, while mild phenotypes were typically missense mutations.
• Among the 35 female relatives, 18 carriers were identified, all from the patients' mothers or sisters. No de novo mutations were found, further supporting the X-linked recessive inheritance pattern.
• The study revealed that the average age of diagnosis for MPS II in Kenya is relatively high (8.8 years), and many families have a history of male deaths, indicating significant underdiagnosis and delayed diagnosis in this population.
• Some pathogenic variants (e.g., c.1327C > T) showed inconsistent phenotypes compared to literature, suggesting that genotype-phenotype correlations may vary due to population-specific genetic backgrounds.
• Extended genetic testing found that some patients also carry other pathogenic variants (e.g., in G6PD, APOB, BTD), indicating the potential value of multi-disease genetic screening in resource-limited settings.
• Sociocultural factors significantly influence the acceptance of genetic information, including stigmatization of mothers, distrust of genetic test results, and legal restrictions on pregnancy termination. Therefore, a localized and culturally sensitive genetic counseling model is needed.

Significance and Future Directions
This study is the first systematic analysis of genotype and phenotype characteristics of MPS II in the Kenyan population, providing foundational data for genetic research of the disease in African populations. Researchers emphasize the need to establish newborn screening and carrier testing systems in Kenya to enable early intervention and family planning. The study also calls for the development of genetic testing panels suitable for African populations to avoid misdiagnosis due to missing race-specific variants. Future efforts should include training local genetic counselors, improving primary care physicians' ability to recognize and refer genetic disorders, and exploring low-cost, high-throughput genetic testing solutions.

 

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Conclusion
This article systematically analyzed the genetic mutation profiles and phenotypic manifestations of MPS II patients in Kenya, revealing medical, social, and cultural challenges in implementing genetic testing and counseling in low-income countries. The study found that the genotype-phenotype correlations in Kenyan patients are generally consistent with those in other global populations, but some variants show population-specific phenotypic differences, suggesting the need for genetic testing tools tailored for African populations. Additionally, the study highlights the importance of carrier testing for mothers in family planning and points out that even in regions without access to advanced therapies, early diagnosis can significantly improve patient management. The study urges policymakers to promote newborn screening, establish local genetic counseling systems, and develop low-cost genetic testing platforms to enable early detection and intervention of rare diseases in Africa.

 

Lucy N Wainaina Mungai, Charles Njeru, Allan Njoroge, Beatrice Odongkara, and Danny E Miller. Challenges and opportunities with providing genetic testing and counseling for mucopolysaccharidosis type II in Kenya. Orphanet Journal of Rare Diseases.