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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 49,XXXXY syndrome is a rare sex chromosome anomaly with an approximate incidence of 1 in 85,000 male live births. The diagnosis is usually ascertained postnatally by the association of mental retardation, variable growth deficiency, Down syndrome-like facial dysmorphy, hypogenitalism and other malformations, especially involving the heart and skeleton. Prenatal diagnosis of the pentasomy 49,XXXXY is generally fortuitous and sonographic features have rarely been described in the literature. We report here on two cases of 49,XXXXY syndrome diagnosed prenatally because of sonographic abnormalities. In the first, amniocentesis was performed at 26 weeks' gestation for polyhydramnios, unilateral clubfoot and micropenis. In the second, a karyotype was carried out on chorionic villi at 13 weeks' gestation for cystic hygroma. These observations and the six previously reported cases demonstrate that cystic hygroma in first or second trimester of pregnancy may be associated with sex chromosome aneuploidy other than Turner syndrome. Moreover, they emphasize the importance of detailed sonographic examination in the second trimester, as small penis and abnormal posturing of the lower extremities are very suggestive of the 49,XXXXY syndrome.
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PMID:Prenatal sonographic diagnosis of the 49,XXXXY syndrome. 1247 28

We report an 11-year-old girl with Turner syndrome with 45, X/46, X, mar (X) who had mental retardation. EEG showed remarkable provocation of paroxysmal activity by photic stimulation. Diffuse irregular poly-spike and wave bursts were elicited by photic stimuli, without accompanying by clinical seizure.
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PMID:[Photosensitivity in electroencephalogram of a child with 45, X/46, X, mar (X) Turner Syndrome]. 1275 57

Turner syndrome females (45,X) do not have mental retardation (MR), whereas some mosaic ring X Turner syndrome females, with 45,X/46,X,r(X), have severe MR. The MR is believed to be caused by a failure of X chromosome inactivation (XCI) of the small ring X chromosome, which leads to functional X disomy (FXD), To explore this hypothesis, we examined the proportion of FXD cells in the peripheral blood of four ring X Turner syndrome females with various levels of MR, using two newly developed XCI assays based on DNA methylation of X-linked genes. As a result, the two patients with extremely severe MR showed complete FXD patterns, whereas the remaining two patients with relatively milder MR showed partial FXD patterns. These results indicate that the proportion of FXD cells may be associated with the severity of MR in mosaic ring X Turner syndrome females, although this association should be confirmed by examining brain cells during development. One of the cases with severe MR and a complete FXD pattern neither lacked the XIST gene nor had uniparental X isodisomy, and we discuss the mechanism of the failure of XCI in this case.
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PMID:The proportion of cells with functional X disomy is associated with the severity of mental retardation in mosaic ring X Turner syndrome females. 1290 May 75

We studied a new series of 21 individuals mosaic for a ring X chromosome [r(X)]. Of nine individuals with mental retardation, only one had a r(X) that lacked XIST (X-inactive-specific transcript) and was not subject to X inactivation, which would explain the abnormal phenotype; the remaining eight cases had XIST on their r(X). The majority of cases (five of seven) with mental retardation had an apparently early replicating r(X); but the androgen receptor gene (AR) was methylated on one allele in five of six informative cases, including two cases with an early replicating r(X). These conflicting results on two indicators of X inactivation suggest a potential dissociation between late replication and DNA methylation in these r(X) chromosomes, which may fail to become completely silenced. Of the twelve subjects who were not mentally retarded, all had XIST present on their r(X) and most (8/10) showed a late replicating r(X), together with AR methylation in all five informative cases, indicating r(X) inactivation. Thus, the unusual phenotypic features and mental retardation associated with the presence of a r(X) cannot be explained solely on the basis of presence or absence of XIST. The r(X) in cases with mental retardation were consistently smaller than those in individuals with normal intelligence, perhaps indicating inability for small rings to undergo structural changes associated with complete X inactivation or lethality in cases with a large non-inactivated r(X). Of the Turner syndrome features present in the r(X) cases, only edema was present in a lesser frequency than in 45,X individuals. Our cases generally had a less severe phenotype than those previously reported, suggesting that reported incidences of abnormalities may be influenced by ascertainment bias, with mental retardation potentially unrelated to the presence of the r(X) in some cases.
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PMID:Phenotype and X inactivation in 45,X/46,X,r(X) cases. 1521 49

Rearranged X chromosome in Turner syndrome (TS) are generally well tolerated but in cases of ring X chromosomes and of X/autosome translocations the incidence of mental retardation and other congenital abnormalities can be significantly higher. These abnormal phenotypes can be ascribed to failed or partial X inactivation. Here, we report a 10-year-old female who was referred for a cytogenetic analysis because she developed an alopecia universalis. The patient, of normal intelligence, had been found to have traits of TS, especially short stature. A first cytogenetic analysis showed a no mosaic 45,X karyotype. Since, the risk of developing gonadoblastoma in TS patients with mosaicism for a Y derivative chromosome and because association of alopecia universalis and TS is uncommon, fluorescence in situ hybridization (FISH) was performed to search for a second cell population. Our patient was found to have a mosaic 45,X/46,X,+r. FISH analysis using sex chromosome probes permitted us to identify the very small marker as a ring X chromosome, detected in 90% of cells. The ring appeared to be formed almost totally of alphoid sequences with breakpoints in the juxtacentromeric region. The r(X) does not include the XIST locus and may, therefore, not be subject to X-inactivation. Unexpectedly mild phenotype in our patient and its association with alopecia universalis will be discussed.
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PMID:Turner syndrome female with a small ring X chromosome lacking the XIST, an unexpectedly mild phenotype and an atypical association with alopecia universalis. 1533 77

Although epilepsy and mental retardation are commonly observed in individuals with chromosomal aberrations, the identification of EEG/epileptic profiles in those with specific chromosome anomalies remains difficult. A few syndromes seem to show peculiar clinical and EEG associations. The authors report an electroclinical investigation on a group of patients carrying X chromosome anomalies: 16 patients with Turner's syndrome, 17 with Klinefelter's syndrome, 1 with an X-autosomal rearrangement, 2 with Xq isochromosome [Xq(i)], and 7 with triple X syndrome. Epilepsy and/or EEG anomalies were found in three of the patients with Klinefelter's syndrome, in one patient with an X-autosomal rearrangement, and in five of those with triple X syndrome. No epilepsy or EEG anomalies were detected in the other patients. Epilepsy may be associated with Klinefelter's syndrome. In addition, the authors found that an electroclinical pattern, represented by paroxysmal activity in the posterior regions (temporo-parieto-occipital areas) with complex partial seizures and easily controlled by antiepileptic drugs, may be present in patients with triple X syndrome. In contrast, gross X-autosomal rearrangements are associated with polymorphic EEG/epileptic findings. Although further studies are needed to validate these observations, they clearly confirm the strict relationship between X chromosome anomalies and epilepsy.
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PMID:Electroencephalographic and epileptic patterns in X chromosome anomalies. 1550 14

Turner syndrome is a complex and common genetic disorder that affects women and is associated with a wide variety of anatomic and physiological disorders. These abnormalities, especially those relating to the airway and cardiovascular system, pose a challenge to the anesthesiologist. We report a case of Turner syndrome associated with mental retardation and difficult airway, followed by a discussion of the perioperative management and review of the relevant literature. We also provide a concise tabular summary of the many problems associated with Turner syndrome and give guidelines for a systematic perioperative approach.
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PMID:Anesthetic management of Turner syndrome: a systematic approach. 1580 30

The X chromosome plays an important role in brain development and function, as evidenced by its disproportionately high content of genes whose mutations cause mental retardation. These X-linked brain genes may play a role in sexual differentiation if they are expressed at a higher level in XX females than in XY males, due to incomplete X inactivation in females. The expression of several X escapee genes is indeed higher in brain tissues from females when compared to males. In mouse, some of the sex differences are only found in adult brains but not in other tissues. Determining the brain expression pattern of these X escapee genes is important for a better understanding of their role in the neurological phenotypes of XO Turner syndrome.
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PMID:Sex differences in brain expression of X- and Y-linked genes. 1696 77

Turner's syndrome (TS) is a chromosomal disorder that results from the loss of the entire or a part of the X-chromosome and occurs in 1/2,500 female births. According to the majority of specific reports, intelligence in TS is generally found to be normal and the prevalence of mental retardation does not seem to be increased in TS except for those patients with a small ring X-chromosome. We evaluated 33 girls with TS with chronological age from 6-18 years. Intellectual assessment included the WISC III and the WAIS-R scales. Our results showed: 1) mean full scale intelligence quotient (FSIQ) was significantly lower than expected based on normative data (p < 0.0005); 2) no correlation was present between height and general intellectual ability; 3) mean performance intelligence quotient (PIQ) was significantly lower than both mean verbal intelligence quotient (VIQ) and FSIQ (p < 0.0025 and p < 0.01, respectively), and most patients had a VIQ-PIQ discrepancy; 4) the frequency of mental retardation in our study group was significantly higher than that observed in the general population (15.1% vs 2.3%, p < 0.025); 5) a significant association was found between karyotype and VIQ, and the best score was achieved in the subgroup of patients with structural abnormalities of the X-chromosome. In the light of these findings we conclude that the clinical picture in TS may encompass a slightly reduced FSIQ, VIQ and especially an inadequate PIQ, but this neurocognitive profile is not significantly affected by statural impairment. Since these neurocognitive defects can be responsible for misdiagnosed school difficulties, we suggest that girls with TS should receive specialized educational support and multidisciplinary care.
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PMID:Neurocognitive profile in Turner's syndrome is not affected by growth impairment. 1766 92

Marker or ring X chromosomes are frequently seen in Ullrich-Turner Syndrome with 46,X,r(X) karyotype, but only 8 children were reported with an extra marker X chromosome in at least some of their cell lines, we describe a 5 years old male patient who is mosaic (17%) for a cell line with an extra ring shaped marker X chromosome in addition to a normal 46,XY cell line. He had mild motor mental retardation, a dysmorphic face, dysplastic ears, high arched palate, cryptorchidism and brachydactyly. G-banding showed 46,XY[83]/47,XY,+r?[17] karyotype. NOR banding revealed no satellite region but its centromere was intact in C-banding. By fluorescent in situ hybridization (FISH) technique, dual X/Y alpha-satellite probes were used to detect the origin of ring shaped marker chromosome and 17% of his cells had two X chromosome signals due to marker X; hybridization with X chromosome inactivation center (XIST) specific probe revealed the absence of the locus on the ring chromosome. In this report, clinical features of our patient are compared with previously reported cases and the cytogenetic and molecular cytogenetic techniques used to detect origin of marker chromosome are discussed.
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PMID:A boy with small supernumerary marker chromosome X identified by FISH. 1828 20


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