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Open AccessArticle

Cascade Testing for Fragile X Syndrome in a Rural Setting in Cameroon (Sub-Saharan Africa)

1
Division of Human Genetics, Department of Pathology & Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town 7700, South Africa
2
Department of Paediatrics, Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaounde, Cameroon
3
National Health Laboratory Service, Groote Schuur Hospital, Cape Town 7925, South Africa
4
Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town 7700, South Africa
*
Author to whom correspondence should be addressed.
Genes 2020, 11(2), 136; https://doi.org/10.3390/genes11020136
Received: 26 December 2019 / Revised: 13 January 2020 / Accepted: 22 January 2020 / Published: 28 January 2020
(This article belongs to the Special Issue Genetics of Intellectual Disability)
Fragile X Syndrome (FXS), an X-linked dominant monogenic condition, is the main genetic cause of intellectual disability (ID) and autism spectrum disorder (ASD). FXS is associated with an expansion of CGG repeat sequence in the Fragile X Mental Retardation gene 1 (FMR1) on chromosome X. Following a neuropediatric assessment of two male siblings who presented with signs of FXS that was confirmed with molecular testing, we provided cascade counselling and testing to the extended family. A total of 46 individuals were tested for FXS; among them, 58.70% (n = 27) were females. The mean age was 9.4 (±5) years for children and 45.9 (±15.9) years for adults. Pedigree analysis suggested that the founder of these families was likely a normal transmitting male. Four out of 19 males with clinical ID were confirmed to have a full mutation for FXS, while 14/27 females had a pathologic CGG expansion (>56 CGG repeats) on one of their X chromosomes. Two women with premature menopause were confirmed of being carriers of premutation (91 and 101 CGG repeats). We also identified maternal alleles (91 and 126 CGG repeats) which expanded to a full mutation in their offspring (>200 CGG repeats). This study is a rare report on FXS from Africa and illustrates the case scenario of implementing genetic medicine for a neurogenetic condition in a rural setting.
Keywords: fragile X syndrome; genetic counselling; full mutation; premutation; Cameroon; Africa fragile X syndrome; genetic counselling; full mutation; premutation; Cameroon; Africa
MDPI and ACS Style

Kengne Kamga, K.; Nguefack, S.; Minka, K.; Wonkam Tingang, E.; Esterhuizen, A.; Nchangwi Munung, S.; De Vries, J.; Wonkam, A. Cascade Testing for Fragile X Syndrome in a Rural Setting in Cameroon (Sub-Saharan Africa). Genes 2020, 11, 136.

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