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Fragile X syndrome in Japanese patients with infantile autism
T Matsuishi1, Y Shiotsuki, N Niikawa
1Department of Pediatrics, Kurume University School of Medicine, Japan.
Insights
Fragile X syndrome was found in 2.6% of male children with infantile autism in this study. This genetic condition, fragile X chromosome, was detected using specific cell culture methods.
Area of Science:
- Genetics
- Developmental Neuroscience
- Clinical Cytogenetics
Background:
- Infantile autism is a complex neurodevelopmental disorder.
- The fragile X [fra(X)] syndrome is a known genetic cause of intellectual disability and autism spectrum disorder.
- Cytogenetic investigation is crucial for identifying underlying genetic factors in autism.
Purpose of the Study:
- To investigate the prevalence of fragile X [fra(X)] syndrome in a cohort of patients diagnosed with infantile autism according to DSM III criteria.
- To evaluate the sensitivity of different cell culture methods for detecting the fragile X chromosome.
Main Methods:
- Cytogenetic analysis of peripheral blood lymphocytes from 47 autistic patients (39 males, 8 females).
- Screening for fra(X) chromosome using lymphocyte cultures deficient in folic acid.
- Confirmation of fra(X) chromosome presence using a secondary culture method with 5-fluoro-2'-deoxyuridine.
Main Results:
- The fragile X chromosome was detected in 2 out of 39 male patients (2.6%), who were siblings.
- No fra(X) chromosome was found in the 8 female patients.
- Variable frequencies of fra(X) expression were observed in the affected siblings and their mother.
Conclusions:
- Fragile X syndrome is present in a subset of male patients with infantile autism.
- The 5-fluoro-2'-deoxyuridine method demonstrated higher sensitivity for fra(X) chromosome detection, particularly in suspected carriers.
- Cytogenetic screening for fragile X syndrome is recommended in male children diagnosed with autism.
Abstract:
Forty-seven patients (39 boys and 8 girls) with infantile autism whose clinical symptoms had matched the diagnostic criteria of DSM III were studied cytogenetically for the occurrence of fragile X [fra(X)] syndrome. The existence of fra(X) chromosome in these patients was screened first by culturing peripheral blood lymphocytes in a medium in which folic acid was absent; the fra(X) chromosome then was confirmed by reculturing in another medium to which 5-fluoro-2'-deoxyuridine was added for the last 24 hours of culture. Fra(X) chromosome was found in 2 of 39 male patients, but in none of the female patients; the 2 patients are siblings. Thus, fra(X) syndrome occurs in 2.6% (1/38) in this study population of male autistic children. The frequencies of fra(X) expression in the older brother with mild mental retardation, in the more severely retarded younger brother, and in their mother were 3-5%, 17-20%, and 9-3%, respectively. Of the two methods used in the present study, the method employing 5-fluoro-2'-deoxyuridine tended to be more sensitive to fra(X) chromosome detection, especially for a suspected carrier.