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Govender KC, Pillay S. Palmoplantar keratoderma, pseudo-ainhum and knuckle pads in an African patient: A case report. SAGE Open Med Case Rep 2023; 11:2050313X231204197. [PMID: 37846342 PMCID: PMC10576918 DOI: 10.1177/2050313x231204197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 09/12/2023] [Indexed: 10/18/2023] Open
Abstract
Hereditary palmoplantar keratoderma is a rare heterogenous group of genodermatoses characterised by hyperkeratosis of the palms and soles. Genetic alterations affecting proteins of the keratin cytoskeleton, cornified cell envelope, desmosomes and gap junction proteins have been implicated in the pathogenesis of inherited palmoplantar keratoderma. Reports of palmoplantar keratoderma in the African population are scarce. Herein, we report a case of a 29-year-old HIV-infected African female, who presented to a tertiary hospital with complaints of a painful left fourth toe, secondary to a constriction band. Her background history is significant for prior constriction bands involving her toes, some of which progressed to auto-amputations and childhood-onset thickening of the palmoplantar skin. Examination revealed diffuse transgrediens palmoplantar keratoderma with associated clinical findings of pseudo-ainhum and knuckle pads. A systemic workup was non-contributory. Next-generation sequencing genetic testing detected two variants of undetermined significance in gap junction protein beta 4, a connexin-encoding gene, and in the rhomboid 5 homolog 2 gene. Her phenotype remains discordant with our genetic findings. Her clinical features are instead consistent with overlapping phenotypes of gap junction protein beta 2-related connexin disorders: Vohwinkel syndrome and Bart-Pumphrey syndrome. Our case underlines the genetic heterogeneity of palmoplantar keratoderma and the diagnostic challenges it presents. Our patient required surgical amputation of the affected toe and is receiving ongoing dermatological management. Early recognition, appropriate referral and management are required to avert the debilitating consequences of mutilating keratoderma and improve the quality of life.
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Affiliation(s)
| | - Somasundram Pillay
- Department of Internal Medicine, King Edward VIII Hospital, Durban, South Africa
- University of Kwa-Zulu Natal, School of Clinical Medicine, Durban, South Africa
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2
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Alsabbagh MM. Keratitis-ichthyosis-deafness syndrome: A comprehensive review of cutaneous and systemic manifestations. Pediatr Dermatol 2023; 40:19-27. [PMID: 36444857 DOI: 10.1111/pde.15201] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 11/05/2022] [Indexed: 11/30/2022]
Abstract
Keratitis-ichthyosis-deafness syndrome is a rare genetic disease presenting with cutaneous, ocular, and otic defects. This comprehensive review provides insight into the clinical presentations, highlighting the cutaneous manifestations including histopathology and treatment options.
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Affiliation(s)
- Manahel Mahmood Alsabbagh
- Department of Molecular Medicine, Princess Al-Jawhara Center for Molecular Medicine and Inherited Disorders, Arabian Gulf University, Manama, Kingdom of Bahrain
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3
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Adadey SM, Wonkam-Tingang E, Aboagye ET, Quaye O, Awandare GA, Wonkam A. Hearing loss in Africa: current genetic profile. Hum Genet 2021; 141:505-517. [PMID: 34609590 PMCID: PMC9034983 DOI: 10.1007/s00439-021-02376-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/21/2021] [Indexed: 01/03/2023]
Abstract
Hearing impairment (HI) is highly heterogeneous with over 123 associated genes reported to date, mostly from studies among Europeans and Asians. Here, we performed a systematic review of literature on the genetic profile of HI in Africa. The study protocol was registered on PROSPERO, International Prospective Register of Systematic Reviews with the registration number “CRD42021240852”. Literature search was conducted on PubMed, Scopus, Africa-Wide Information, and Web of Science databases. A total of 89 full-text records was selected and retrieved for data extraction and analyses. We found reports from only 17/54 (31.5%) African countries. The majority (61/89; 68.5%) of articles were from North Africa, with few reports found from sub-Saharan Africa. The most common method used in these publications was targeted gene sequencing (n = 66/111; 59.5%), and only 13.5% (n = 15/111) used whole-exome sequencing. More than half of the studies were performed in families segregating HI (n = 51/89). GJB2 was the most investigated gene, with GJB2: p.(R143W) founder variant only reported in Ghana, while GJB2: c.35delG was common in North African countries. Variants in MYO15A were the second frequently reported in both North and Central Africa, followed by ATP6V1B1 only reported from North Africa. Usher syndrome was the main syndromic HI molecularly investigated, with variants in five genes reported: USH2A, USH1G, USH1C, MYO7A, and PCDH15. MYO7A: p.(P1780S) founder variant was reported as the common Usher syndrome variant among Black South Africans. This review provides the most comprehensive data on HI gene variants in the largely under-investigated African populations. Future exomes studies particularly in multiplex families will likely provide opportunities for the discovery of the next sets of novel HI genes, and well as unreported variants in known genes to further our understanding of HI pathobiology, globally.
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Affiliation(s)
- Samuel Mawuli Adadey
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana.,Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, 7925, South Africa
| | - Edmond Wonkam-Tingang
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, 7925, South Africa
| | - Elvis Twumasi Aboagye
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana
| | - Osbourne Quaye
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana
| | - Gordon A Awandare
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, 7925, South Africa.
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4
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Cammarata-Scalisi F, Willoughby CE, Cárdenas Tadich A, Labrador N, Herrera A, Callea M. Clinical, etiopathogenic, and therapeutic aspects of KID syndrome. Dermatol Ther 2020; 33:e13507. [PMID: 32367610 DOI: 10.1111/dth.13507] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/20/2020] [Accepted: 04/28/2020] [Indexed: 11/26/2022]
Abstract
Keratitis-ichthyosis-deafness (KID syndrome) is a syndromes ichthyoses that is clinically and genetically heterogeneous requiring early and long-term multidisciplinary monitoring of affected individuals. A review of the clinical, etiopathogenic and therapeutic aspects is presented of this rare congenital ectodermal disorder.
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Affiliation(s)
| | | | | | | | - Adriana Herrera
- Ophthalmology Unit, University of Los Andes, Mérida, Venezuela
| | - Michele Callea
- Unit of Dentistry, Bambino Gesù Children' Hospital, IRCCS, Rome, Italy
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5
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Abstract
The incidence of hearing impairment (HI) is higher in low- and middle-income countries when compared to high-income countries. There is therefore a necessity to estimate the burden of this condition in developing world. The aim of our study was to use a systematic approach to provide summarized data on the prevalence, etiologies, clinical patterns and genetics of HI in Cameroon. We searched PubMed, Scopus, African Journals Online, AFROLIB and African Index Medicus to identify relevant studies on HI in Cameroon, published from inception to 31 October, 2019, with no language restrictions. Reference lists of included studies were also scrutinized, and data were summarized narratively. This study is registered with PROSPERO, number CRD42019142788. We screened 333 records, of which 17 studies were finally included in the review. The prevalence of HI in Cameroon ranges from 0.9% to 3.6% in population-based studies and increases with age. Environmental factors contribute to 52.6% to 62.2% of HI cases, with meningitis, impacted wax and age-related disorder being the most common ones. Hereditary HI comprises 0.8% to 14.8% of all cases. In 32.6% to 37% of HI cases, the origin remains unknown. Non-syndromic hearing impairment (NSHI) is the most frequent clinical entity and accounts for 86.1% to 92.5% of cases of HI of genetic origin. Waardenburg and Usher syndromes account for 50% to 57.14% and 8.9% to 42.9% of genetic syndromic cases, respectively. No pathogenic mutation was described in GJB6 gene, and the prevalence of pathogenic mutations in GJB2 gene ranged from 0% to 0.5%. The prevalence of pathogenic mutations in other known NSHI genes was <10% in Cameroonian probands. Environmental factors are the leading etiology of HI in Cameroon, and mutations in most important HI genes are infrequent in Cameroon. Whole genome sequencing therefore appears as the most effective way to identify variants associated with HI in Cameroon and sub-Saharan Africa in general.
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6
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Wonkam Tingang E, Noubiap JJ, F. Fokouo JV, Oluwole OG, Nguefack S, Chimusa ER, Wonkam A. Hearing Impairment Overview in Africa: the Case of Cameroon. Genes (Basel) 2020; 11:genes11020233. [PMID: 32098311 PMCID: PMC7073999 DOI: 10.3390/genes11020233] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 02/15/2020] [Accepted: 02/19/2020] [Indexed: 01/27/2023] Open
Abstract
The incidence of hearing impairment (HI) is higher in low- and middle-income countries when compared to high-income countries. There is therefore a necessity to estimate the burden of this condition in developing world. The aim of our study was to use a systematic approach to provide summarized data on the prevalence, etiologies, clinical patterns and genetics of HI in Cameroon. We searched PubMed, Scopus, African Journals Online, AFROLIB and African Index Medicus to identify relevant studies on HI in Cameroon, published from inception to 31 October, 2019, with no language restrictions. Reference lists of included studies were also scrutinized, and data were summarized narratively. This study is registered with PROSPERO, number CRD42019142788. We screened 333 records, of which 17 studies were finally included in the review. The prevalence of HI in Cameroon ranges from 0.9% to 3.6% in population-based studies and increases with age. Environmental factors contribute to 52.6% to 62.2% of HI cases, with meningitis, impacted wax and age-related disorder being the most common ones. Hereditary HI comprises 0.8% to 14.8% of all cases. In 32.6% to 37% of HI cases, the origin remains unknown. Non-syndromic hearing impairment (NSHI) is the most frequent clinical entity and accounts for 86.1% to 92.5% of cases of HI of genetic origin. Waardenburg and Usher syndromes account for 50% to 57.14% and 8.9% to 42.9% of genetic syndromic cases, respectively. No pathogenic mutation was described in GJB6 gene, and the prevalence of pathogenic mutations in GJB2 gene ranged from 0% to 0.5%. The prevalence of pathogenic mutations in other known NSHI genes was <10% in Cameroonian probands. Environmental factors are the leading etiology of HI in Cameroon, and mutations in most important HI genes are infrequent in Cameroon. Whole genome sequencing therefore appears as the most effective way to identify variants associated with HI in Cameroon and sub-Saharan Africa in general.
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Affiliation(s)
- Edmond Wonkam Tingang
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
| | - Jean Jacques Noubiap
- Centre for Heart Rhythm Disorders, South Australian Health and Medical Research Institute (SAHMRI), University of Adelaide and Royal Adelaide Hospital, Adelaide 5000, Australia;
| | | | - Oluwafemi Gabriel Oluwole
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
| | - Séraphin Nguefack
- Department of Paediatrics, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé 1364, Cameroon;
- Paediatrics unit, Gynaeco-Obstetric and Paediatric Hospital, Yaoundé 4362, Cameroon
| | - Emile R. Chimusa
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
| | - Ambroise Wonkam
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
- Department of Medicine, University of Cape Town, Cape Town 7925, South Africa
- Correspondence: ; Tel.: +27-21-4066-307
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7
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Dalamón VK, Buonfiglio P, Larralde M, Craig P, Lotersztein V, Choate K, Pallares N, Diamante V, Elgoyhen AB. Connexin 26 (GJB2) mutation in an Argentinean patient with keratitis-ichthyosis-deafness (KID) syndrome: a case report. BMC MEDICAL GENETICS 2016; 17:37. [PMID: 27141831 PMCID: PMC4855445 DOI: 10.1186/s12881-016-0298-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 04/22/2016] [Indexed: 11/20/2022]
Abstract
Background Keratitis-Ichthyosis-Deafness (KID) syndrome is a rare condition characterized by pre-lingual sensorineural deafness with skin hyperkeratinization. The primary cause of the disease is a loss-of-function mutation in the GJB2 gene. Mutations in Argentinean patients have not been described. Case presentation We studied a 2 year-old boy with bilateral congenital sensorineural deafness with dry skin over the entire body, hypotrichosis of the scalp, thin and light-blond hair. Analysis of the GJB2 gene nucleotide sequence revealed the substitution of guanine-148 by adenine predicted to result in an Asp50Asn amino acid substitution. Conclusion This is the first KID report in a patient from Argentina. This de novo mutation proved to be the cause of keratitis-ichthyosis-deafness syndrome (KID-syndrome) in the patient, and has implications in medical genetic practice.
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Affiliation(s)
- Viviana Karina Dalamón
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor Torres"-(INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490. (1428) Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
| | - Paula Buonfiglio
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor Torres"-(INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490. (1428) Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Margarita Larralde
- Servicio de Dermatología Pediátrica, Hospital Ramos Mejía, Ciudad Autonoma de Buenos Aires, Argentina.,Departamento de Dermatología, Hospital Alemán, Ciudad Autonoma de Buenos Aires, Argentina
| | - Patricio Craig
- Departamento de Química Biológica e Instituto de Química y Fisicoquímica Biológicas, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autonoma de Buenos Aires, Argentina
| | - Vanesa Lotersztein
- Servicio de Genética, Hospital de Clínicas "José de San Martín", Ciudad Autonoma de Buenos Aires, Argentina
| | - Keith Choate
- Dermatology Yale University School of Medicine, New Haven, USA
| | - Norma Pallares
- Instituto Superior de Implantes Cocleares "Dr. Vicente Diamante", Ciudad Autonoma de Buenos Aires, Argentina
| | - Vicente Diamante
- Instituto Superior de Implantes Cocleares "Dr. Vicente Diamante", Ciudad Autonoma de Buenos Aires, Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor Torres"-(INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490. (1428) Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.,Departamento de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina
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8
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Kombaté K, Saka B, Landoh DE, Mouhari-Toure A, Akakpo S, Belei E, Gnassingbé W, Djibril MA, Tchangaï-Walla K, Pitché P. [Keratitis-Ichthyosis-Deafness syndrome (KID) in a Togolese child born from a consanguineous marriage]. Pan Afr Med J 2015; 21:266. [PMID: 26664520 PMCID: PMC4646290 DOI: 10.11604/pamj.2015.21.266.6857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Accepted: 06/15/2015] [Indexed: 11/05/2022] Open
Abstract
Le syndrome KID est une affection génétique rare associant kératite, ichtyose et surdité. Nous rapportons un cas dont la surdité s'est compliquée de mutisme chez un enfant togolais issu d'un mariage consanguin.Il s'agissait d'une fillette de 9 ans admise en dermatologie pour une peau sèche et une kératodermie palmoplantaire évoluant depuis l'enfance, une surdité sévère et un mutisme total évoluant depuis la naissance. Il n'y avait pas d'histoire familiale connue de syndrome KID. Les parents de cet enfant sont des cousins germains. A l'examen, on notait une kératodermie palmoplantaire typique en cuir grossier, une peau sèche ichtyosiforme finement squameuse avec un aspect pachydermique aux genoux et un aspect arlequin aux jambes. L'examen ophtalmologique avait noté une blépharo-conjonctivite, une xérophtalmie, une photophobie et une absence de sourcils. L'examen ORL avait objectivé une hypotrophie des pavillons des oreilles, une surdité sévère et un mutisme total. La particularité de cette observation réside dans la sévérité de l'atteinte auditive qui s'est compliquée de mutisme. Notre enfant étant née de parents consanguins sains, sans histoire familiale de KID, nous pensons que le mode de transmission est probablement sporadique. Une étude moléculaire du cas index et de ses parents, non réalisée à cause de notre plateau technique limité aurait pu le confirmer.
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Affiliation(s)
- Koussak Kombaté
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Bayaki Saka
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Dadja Essoya Landoh
- Ministère de la Santé, Division de l'Epidémiologie, Lomé, Togo,Corresponding author: Dadja Essoya Landoh, Ministère de la Santé, Division de l'Epidémiologie, Lomé, Togo
| | - Abass Mouhari-Toure
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Séfako Akakpo
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Eric Belei
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Wanguena Gnassingbé
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Mohaman Awalou Djibril
- Service de Médecine Interne, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Kissem Tchangaï-Walla
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
| | - Palokinam Pitché
- Service de Dermatologie-Vénéréologie, CHU Lomé, Faculté des Sciences de la Santé, Université de Lomé, Lomé, Togo
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9
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Yao F, Yue M, Zhang C, Zuo X, Zheng X, Zhang A, Wang Z, Liu S, Li H, Meng L, Zeng M, Fan X, Sun L, Zhang X. A genetic coding variant rs72474224 in GJB2 is associated with clinical features of psoriasis vulgaris in a Chinese Han population. ACTA ACUST UNITED AC 2015; 86:134-8. [PMID: 26104599 DOI: 10.1111/tan.12595] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/22/2015] [Accepted: 05/22/2015] [Indexed: 12/19/2022]
Abstract
Our recent targeted sequencing study identified a missense single-nucleotide polymorphism rs72474224 (c.324C>T) in GJB2. To investigate the correlation between rs72474224 (c.324C>T) and subphenotypes of psoriasis, genotype data for rs72474224 (c.324C>T, p.Val37Ile) was analyzed in 9946 cases and 9906 controls. The additive model provided the best fit for rs72474224 (P = 7.34 × 10(-9)). The genotypic and allelic frequency distributions were associated with plaque psoriasis in case-only (Pgenotype = 2.67 × 10(-3), Pallele = 6.22 × 10(-4)) and subphenotype-control (Pgenotype = 1.58 × 10(-11), Pallele = 8.16 × 10(-12)) analyses. No other significant difference was found in case-only analyses. Rs72474224 in GJB2 is preferentially associated with plaque psoriasis in Chinese population and might contribute to the complexity of psoriasis clinical features.
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Affiliation(s)
- F Yao
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China.,Department of Dermatology at Anqing Hospital, Anhui Medical University, Hefei, China
| | - M Yue
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - C Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zuo
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zheng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - A Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - Z Wang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - S Liu
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - H Li
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - L Meng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - M Zeng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Fan
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - L Sun
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
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10
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Lebeko K, Bosch J, Noubiap JJN, Dandara C, Wonkam A. Genetics of hearing loss in Africans: use of next generation sequencing is the best way forward. Pan Afr Med J 2015; 20:383. [PMID: 26185573 PMCID: PMC4499266 DOI: 10.11604/pamj.2015.20.383.5230] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 09/27/2014] [Indexed: 11/11/2022] Open
Abstract
Hearing loss is the most common communication disorder affecting about 1-7/1000 births worldwide. The most affected areas are developing countries due toextensively poor health care systems. Environmental causes contribute to 50-70% of cases, specifically meningitis in sub-Saharan Africa. The other 30-50% is attributed to genetic factors. Nonsyndromic hearing loss is the most common form of hearing loss accounting for up to 70% of cases. The most common mode of inheritance is autosomal recessive. The most prevalent mutations associated with autosomal recessive nonsyndromic hearing loss (ARNSHL) are found within connexin genes such as GJB2, mostly in people of European and Asian origin. For example, the c.35delG mutation ofGJB2 is found in 70% of ARNSHL patients of European descentand is rare in populations of otherethnicities. Other GJB2 mutations have been reported in various populations. The second most common mutations are found in theconnexin gene, GJB6, also with a high prevalencein patients of European descent. To date more than 60 genes have been associated with ARNSHL. We previously showed that mutations in GJB2, GJB6 and GJA1 are not significant causes of ARNSHL inpatients from African descents, i.e. Cameroonians and South AfricansIn order to resolve ARNSHL amongst sub-Saharan African patients, additional genes would need to be explored. Currently at least 60 genes are thought to play a role in ARNSHL thus the current approach using Sanger sequencing would not be appropriate as it would be expensive and time consuming. Next Generation sequencing (NGS) provides the best alternative approach. In this review, we reported on the success of using NGSas observed in various populations and advocate for the use of NGS to resolve cases of ARNSHL in sub-Saharan African populations.
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Affiliation(s)
- Kamogelo Lebeko
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Jason Bosch
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | | | - Collet Dandara
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa ; Institute for Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Common genes for non-syndromic deafness are uncommon in sub-Saharan Africa: a report from Nigeria. Int J Pediatr Otorhinolaryngol 2014; 78:1870-3. [PMID: 25218342 PMCID: PMC4208623 DOI: 10.1016/j.ijporl.2014.08.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 08/10/2014] [Accepted: 08/11/2014] [Indexed: 02/02/2023]
Abstract
INTRODUCTION Little is known about the molecular epidemiology of deafness in sub-Saharan Africa (SSA). Even in Nigeria, the most populous African nation, no genetic studies of deafness have been conducted. This pioneering work aims at investigating the frequencies of gene mutations relatively common in other parts of the world (i.e. those in GJB2, GJB6, and mitochondrial DNA) among subjects from Nigeria with hearing loss (HL) with no evidence of acquired pathology or syndromic findings. In addition, we review the literature on the genetics of deafness in SSA. METHOD We evaluated 81 unrelated deaf probands from the Yoruba tribe residing in Ibadan, a suburban city in Nigeria, for the aetiology of their deafness. Subjects underwent genetic testing if their history was negative for an environmental cause and physical examination did not find evidence of a syndrome. Both exons of GJB2 and mitochondrial DNA flanking the 1555A>G mutations were PCR-amplified followed by Sanger sequencing. GJB6 deletions were screened via quantitative PCR. RESULT We identified 44 probands who had nonsyndromic deafness with no environmental cause. The age at study time ranged between 8 months and 45 years (mean=24 years) and age at onset was congenital or prelingual (<age 2 years) in 37 (84%) probands and postlingual in 7 (16%) probands. Among these, 35 probands were the only affected members of their families (simplex cases), while there were at least two affected family members in nine cases (multiplex). Molecular analyses did not show a pathogenic variant in any one of the 44 probands studied. CONCLUSION GJB2, GJB6 and mitochondrial DNA 1555A>G mutations were not found among this initial cohort of the deaf in Nigeria. This makes imperative the search for other genes in the aetiology of HL in this population.
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Bosch J, Noubiap JJN, Dandara C, Makubalo N, Wright G, Entfellner JBD, Tiffin N, Wonkam A. Sequencing of GJB2 in Cameroonians and Black South Africans and comparison to 1000 Genomes Project Data Support Need to Revise Strategy for Discovery of Nonsyndromic Deafness Genes in Africans. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2014; 18:705-10. [PMID: 25162826 DOI: 10.1089/omi.2014.0063] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in the GJB2 gene, encoding connexin 26, could account for 50% of congenital, nonsyndromic, recessive deafness cases in some Caucasian/Asian populations. There is a scarcity of published data in sub-Saharan Africans. We Sanger sequenced the coding region of the GJB2 gene in 205 Cameroonian and Xhosa South Africans with congenital, nonsyndromic deafness; and performed bioinformatic analysis of variations in the GJB2 gene, incorporating data from the 1000 Genomes Project. Amongst Cameroonian patients, 26.1% were familial. The majority of patients (70%) suffered from sensorineural hearing loss. Ten GJB2 genetic variants were detected by sequencing. A previously reported pathogenic mutation, g.3741_3743delTTC (p.F142del), and a putative pathogenic mutation, g.3816G>A (p.V167M), were identified in single heterozygous samples. Amongst eight the remaining variants, two novel variants, g.3318-41G>A and g.3332G>A, were reported. There were no statistically significant differences in allele frequencies between cases and controls. Principal Components Analyses differentiated between Africans, Asians, and Europeans, but only explained 40% of the variation. The present study is the first to compare African GJB2 sequences with the data from the 1000 Genomes Project and have revealed the low variation between population groups. This finding has emphasized the hypothesis that the prevalence of mutations in GJB2 in nonsyndromic deafness amongst European and Asian populations is due to founder effects arising after these individuals migrated out of Africa, and not to a putative "protective" variant in the genomic structure of GJB2 in Africans. Our results confirm that mutations in GJB2 are not associated with nonsyndromic deafness in Africans.
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Affiliation(s)
- Jason Bosch
- 1 Division of Human Genetics, Faculty of Health Sciences, University of Cape Town , Cape Town, South Africa
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