Abstract
Introduction: Fragile X syndrome (FXS) is the commonest inherited cause of intellectual disability. Children with FXS usually present clinically with developmental, learning and behavioural disorders. Physical characteristics of FXS are well documented and are considered a primary guide to recognition. Genetic screening for FXS targets the detection of cytosine-guanine-guanine (CGG) triplet repeats in the FMR1 gene on the X chromosome. Objective: Aim was to estimate the frequency, clinically and genetically, in children referred to a specialist child mental health clinic for preschool and school based learning difficulties. Design and method: A total population of children referred to a specialist mental health service for learning difficulties during a specified period was screened clinically and genetically for FXS. Clinical diagnosis was based on known physical characteristics. They were further assessed on cognitive functions, learning and behaviour. Optimised and validated conventional polymerase chain reaction (PCR) amplification was used for genetic screening where deoxyribonucleic acid (DNA) for the assay was obtained from buccal cells. Results: The total sample studied was 286 children, 4-12 years of age. Based on morphological features, 5.9% received the diagnosis of FXS and one child was genetically positive. Of the rest, 2 more children were genetically positive but clinically negative. Overall frequency of FXS in the study sample was 1.05%. Similar proportions of children earned additional diagnoses of autism and attention deficit and hyperactivity disorder (ADHD) in the two groups but differed in their cognitive functions. Conclusions: The overall frequency of FXS in the study sample was 1.05%.
Highlights
Fragile X syndrome (FXS) is the commonest inherited cause of intellectual disability
Optimised and validated conventional polymerase chain reaction (PCR) amplification was used for genetic screening where deoxyribonucleic acid (DNA) for the assay was obtained from buccal cells
5.9% received the diagnosis of FXS and one child was genetically positive
Summary
Fragile X syndrome (FXS) is the commonest inherited cause of intellectual disability. Children with FXS usually present clinically with developmental, learning and behavioural disorders. Fragile X syndrome (FXS) is an X-linked dominant disorder and is considered the commonest inherited cause of intellectual disability[1]. Children with FXS usually present clinically with developmental delay, learning disability and behaviour problems[1,2]. Physical characteristics of FXS are well documented These include a long and narrow face, large bat-like ears, a prominent jaw and forehead, unusually flexible fingers, flat feet and enlarged testicles in males (macroorchidism) after puberty[3]. The intellectual levels in FXS fall into a wide spectrum, ranging from severe disability to mild or borderline[1,2]. Males are said to be more severely affected[1,2]
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