Screening For Fragile X Syndrome Among Neurobehavioural Patients From Kolkata, Eastern India.
Dr.Kanchan Mukhopadhyay,Manovikas Biomedical Research and Diagnostic Centre 482,Madudah,Plot I-24,Sec J,E.M.Bypass,Kolkata-700107,(India)Ph:91-33-4001-9179;Fax: 91-33-2442-8275,Email:firstname.lastname@example.org
Background: Fragile X syndrome (FXS), associated with abnormal functioning of the FMR1 gene, is a major cause for inherited mental retardation (MR). The symptoms which are commonly associated with FXS are also observed in patients suffering from various neuropsychiatric disorders like autism, epilepsy, seizure disorder etc. Thus, the diagnosis of FXS that is solely based on a patientâ€™s physical and behavioural characteristics is very difficult. To avoid a false positive diagnosis which is crucial for better management of the disorder, screening for FXS with easy diagnostic tools becomes extremely important.
Aims: In this study, screening for FXS was carried out among 157 various neurobehavioural patients attending the out patients department of Manovikas Kendra, Kolkata.
Methods and Material: To screen the level of functioning of the FMR1 gene, the percentage of leukocytes expressing the fragile X mental retardation protein (FMRP) was measured by an immunocytochemical method. CGG repeat size was analyzed by PCR amplification and FMR1 promoter methylation status was checked by methylation sensitive-PCR.
Results: Out of 157 patients recruited for this study, only four were confirmed as FXS (3.18% prevalence among neurobehavioural outpatients). 30 distinct alleles with 12-49 CGG repeats were detected, with the 27 and 28 repeats being most common. Premutation alleles were observed in 25 subjects. Molecular biology-based analyses confirmed 5 cases as FXS; four patients were detected with promoter methylation mosaicism and one with full methylation.
Conclusion: In the present investigation, FXS screening was performed on various neurobehavioural outpatients and four were confirmed with the disorder. The CGG repeat alleles that were most frequently observed in this study were different from those found in other studies, indicating a racial or ethnic variation.