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Results for “X-Linked Intellectual Disability”

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At least 415 records · Page 23Linked to original sources
PubMed1984

Fragile-X syndrome ascertained by the presence of macro-orchidism in a 5-month-old infant.

The fragile-X syndrome, an X-linked form of mental retardation, is estimated to affect one in every 1,000 to 2,000 live-born male infants. Most commonly, fragile-X syndrome has been detected only after patients clearly demonstrate developmental delay, and frequently detection occurs only if the family history is consistent with X-linked mental retardation. Macro-orchidism is a finding commonly associated with the fragile-X syndrome. It has been suggested that the sparsity of reports of macro-orchidism among prepubertal boys with the fragile-X syndrome might be due to lack of careful measurement of the tests rather than to initiation of the enlargement at puberty. A 5-month-old infant with fragile-X syndrome, ascertained through testicular enlargement noted by actual measurement of testicular size as part of his physical examination, is reported.

Adult↗
PubMed1983

[X chromosome-linked mental retardation with fragile X chromosome and macro-orchidism].

Description of the first Swiss family with the new syndrome of X-linked mental retardation. The three brothers described are the first of all males traced back for four generations to be affected. In two of the brothers macroorchidism and the fragile X-chromosome were demonstrated, while the third brother died before diagnosis. As expected, the fragile X was not demonstrable in the 75-year-old mother of the three brothers.

Adolescent↗
PubMed1982

[X-linked mental retardation, macro-orchism, and X chromosome fragile site. Presentation of 6 cases in 2 families].

Six males, four adults and two children, with very important mental deficiency and speech disturbances, belonging to two families are presented. The six patients show the clinical peculiarities of the "X-linked mental retardation, macroorchidism, and the Xq27 fragile site", but the chromosomal alteration only was presented in five cases. Patient who did not have the chromosomal defect presented the same IQ than his brothers, but he had a less severe macroorchidism, a better speech and more normal clinical features. One of the patients shows a shorter arm which linkage with the syndrome is discussed.

Adolescent↗
PubMed1982

Fragile X chromosome and X-linked mental retardation.

A family is described in which three normal females transmitted to seven males X-linked mental retardation associated with macro-orchidism and a fragile site on the long arm of the X chromosome -- fra(X)(q27). The affected males also had minor clinical features in common: a large forehead, long face, large ears, a long upper lip and large extremities.

Adolescent↗
PubMed1982

[Fragile X chromosome and X-linked mental retardation (author's transl)].

In males affected by a special form of X-linked mental retardation a characteristic chromosomal abnormality can be demonstrated, - i.e. a fragile site on the long arm of the X chromosome, fra(X) (q27 or 28) (marker-X chromosome). Male carriers are physically normal, but in most cases show macroorchidism. The demonstration of the marker-X chromosome requires special cell culture conditions, above all a folic acid-deficient medium. The frequency of cells with fragile X chromosome varies interindividually, ranging from 2 to 50%. In female heterozygous carriers the number of cells with fra(X) decreases with age and cannot be demonstrated in some cases. Distribution and frequency of X-linked mental retardation with marker-X chromosome and macro-orchidism are discussed, as well as possibilities of prenatal diagnosis of this disorder.

Adolescent↗
PubMed1982

Fragile X-linked mental retardation of macro-orchidism.

A fragile site near the end of the long arm (q) of the X chromosome appears to be directly related to the gene responsible for the mental retardation found among males and some females who possess this variant X chromosome. Macro-orchidism is present in most males studied. Other mild phenotypic similarities may exist. The expression of the fragile X (fra[X]) chromosome is dependent on the concentration of folic acid and thymidine in the culture medium, which partly explains why fra(X) was not noted earlier and connected promptly with X-linked mental retardation. Whereas prenatal diagnosis is now possible, genetic counseling is complicated by recent reports of "intellectually normal" fra(X) males. Further studies are needed to form solid conclusions about intellectual deficits, learning behavior or personality characteristics of fra(X) persons.

Female↗
PubMed1981

Fragile X syndrome: search for phenotypic manifestations at loci for hypoxanthine phosphoribosyltransferase and glucose-6-phosphate dehydrogenase.

The subjects of this study were individuals with the form of X-linked mental retardation that is associated with the presence of a cytologically variant X chromosome having a secondary constriction or "fragile site" at Xq 27-28 (Fra X). Studies were carried out to test the hypothesis that deletions or modifications at neighboring loci occur as a consequence of events at the fragile site. Skin fibroblasts and peripheral blood lymphocytes from affected males were analyzed with respect to the expression of two X-lined enzymes: glucose-6-phosphate dehydrogenase (G6PD) and hypoxanthine phosphoribosyltransferase (HPRT); loci for these enzymes are known to be located in the region of the fragile site. Although the number of cells resistant to thioguanine (HPRT-deficient) obtained from some cultures from one Fra X male and blood cells of another was greater than expected, the frequency of these cells was not increased in cultures from other Fra X males. Furthermore, our results indicate that the G6PD activity and electrophoretic mobility in Fra X males is similar to that in normal cells, thus providing no evidence for the loss of the long-arm telomere in the fragile X syndrome.

Adult↗
PubMed1981

A marker X chromosome associated with nonspecific male mental retardation. The first South African cases.

This report describes the first cases of X-linked mental retardation with a marker X chromosome seen in South Africa, and forms part of an ongoing study. The marker was found in 11 affected males and 1 carrier female in 4 families investigated. The demonstration of the marker X chromosome characterized by a fragile site at the long arm (fra(X) (q27) in association with nonspecific X-linked mental retardation heralds a new era in cytogenetics. The attention of human geneticists everywhere is focused on various aspects of this fascinating phenomenon. It has now become possible to diagnose an apparently common familial cytogenetic condition with a high risk of recurrence and to identify female carriers; perhaps in time we will be able to provide prenatal diagnosis. Because of the familial involvement through X-linked inheritance the syndrome is believed to be more common than trisomy 21. The nature of the association of mental retardation with the marker X chromosome is unknown, but it could be related to close linkage with abnormal gene(s) or due to faulty transcription of the genes beyond the fragile site.

Adult↗
PubMed1995

Fragile X mental retardation syndrome: DNA diagnosis and carrier detection in New Zealand families.

AIMS: To establish a DNA-based test for the diagnosis and carrier detection of fragile X syndrome, and to investigate the nature of the mutation and patterns of inheritance in New Zealand families. METHODS: A probe for the FRAXA region was generated by polymerase chain reaction, cloned in a plasmid vector, and its structure was confirmed by DNA sequencing. This probe was used in a Southern blot assay to detect full mutations or premutations associated with fragile X syndrome in DNA from peripheral blood samples submitted to our laboratory for routine testing. RESULTS: We tested 379 individuals from throughout New Zealand. Full mutations were found in 29 males, leading to a fragile X diagnosis, or confirmation of an earlier cytogenetic diagnosis. Premutations were detected in 45 females and 11 males, all of whom are asymptomatic carriers of the disease. CONCLUSIONS: The DNA test is rapid and accurate, in contrast to the cytogenetic test. It allows unequivocal detection of carriers, enabling effective counselling, prenatal testing, and more generalised screening of at-risk populations. Our discovery of one large pedigree with many carriers and no prior history of X-linked mental retardation demonstrates that the DNA test is appropriate even in apparently sporadic cases of mental retardation.

Blotting, Southern↗
PubMed1994

Genetic analysis of a kindred with X-linked mental handicap and retinitis pigmentosa.

A kindred is described in which X-linked nonspecific mental handicap segregates together with retinitis pigmentosa. Carrier females are mentally normal but may show signs of the X-linked retinitis pigmentosa carrier state and become symptomatic in their later years. Analysis of polymorphic DNA markers at nine loci on the short arm of the X chromosome shows that no crossing-over occurs between the disease and Xp11 markers DXS255, TIMP, DXS426, MAOA, and DXS228. The 90% confidence limits show that the locus is in the Xp21-q21 region. Haplotype analysis is consistent with the causal gene being located proximal to the Xp21 loci DXS538 and 5'-dystrophin on the short arm of the X chromosome. The posterior probability of linkage to the RP2 region of the X chromosome short arm (Xp11.4-p11.23) is .727, suggesting the possibility of a contiguous-gene-deletion syndrome. No cytogenetic abnormality has been identified.

Adolescent↗
PubMed1994

Segregation of FRAXE in a large family: clinical, psychometric, cytogenetic, and molecular data.

During an ongoing study on X-linked mental retardation, we ascertained a large family in which mild mental retardation was cosegregating with a fragile site at Xq27-28. Clinical, psychometric, cytogenetic, and molecular studies were performed. Apart from mild mental retardation, affected males and females did not show a specific clinical phenotype. Psychometric assessment of four representative affected individuals revealed low academic achievements, with verbal and performance IQs of 61-75 and 70-82, respectively. Cytogenetically the fragile site was always present in affected males and was not always present in affected females. With FISH the fragile site was located within the FRAXE region. The expanded GCC repeat of FRAXE was seen in affected males and females either as a discrete band or as a broad smear. No expansion was seen in unaffected males, whereas three unaffected females did have an enlarged GCC repeat. Maternal transmission of FRAXE may lead to expansion or contraction of the GCC repeat length, whereas in all cases of paternal transmission contraction was seen. In striking contrast to the situation in fragile X syndrome, affected males may have affected daughters. In addition, there appears to be no premutation of the FRAXE GCC repeat, since in the family studied here all males lacking the normal allele were found to be affected.

Adolescent↗