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Query: UMLS:C0917816 (mental retardation)
 15,867 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Malformations of the cerebral cortex are being recognized more frequently as a cause of epilepsy, developmental delay, neurological deficits, and mental retardation. Nonetheless, a standard nomenclature and classification system of these malformations, based upon state-of-the art knowledge derived from genetics, embryology, imaging, and pathology, has not been devised. In this manuscript, we propose such a classification system. Moreover, we have constructed the system such that both the framework and the classifications themselves are flexible and can be adapted as our knowledge of the embryology, genetics, imaging, and pathology of these disorders advances. We believe that the use of this classification system will help both clinicians and researchers to understand and think about these disorders and their causes better. In turn, we hope that this improved understanding will lead to further refinements in classification, to advances in our knowledge and, ultimately, to improvements in therapy.
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PMID:A classification scheme for malformations of cortical development. 873 19

Deletions of the short arm of chromosome 6 are relatively rare, only 16 cases having been described in the literature so far. Here we present a detailed investigation by fluorescence in situ hybridisation of two further cases with different but overlapping interstitial deletions involving 6p22, 6p23 and 6p24. The main features involved are craniofacial malformations, heart and kidney defects, mental retardation/developmental delay, hypotonia and hydrocephalus. By using 36 yeast artificial chromosome and cosmid clones from a contig covering 6p22.3-6p25 and other probes with defined cytogenetic locations within 6p21-6p22 we have precisely localised the breakpoints involved in each of the cases, estimated the sizes of the deleted regions and defined the region that is hemizygously deleted in both cases.
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PMID:A detailed investigation of two cases exhibiting characteristics of the 6p deletion syndrome. 879 22

The expression of X-linked genes in females heterozygous for X-linked defects can be modulated by epigenetic control mechanisms that constitute the X chromosome inactivation pathway. At least four different effects have been found to influence, in females, the phenotypic expression of genes responsible for X-linked mental retardation (XLMR). First, non-random X inactivation, due either to stochastic or genetic factors, can result in tissues in which one cell type (for example, that in which the X chromosome carrying a mutant XLMR gene is active) dominates, instead of the normal mosaic cell population expected as a result of random X inactivation. Second, skewed inactivation of the normal X in individuals carrying a deletion of part of the X chromosome has been documented in a number of mentally retarded females. Third, functional disomy of X-linked genes that are expressed inappropriately due to the absence of X inactivation has been found in mentally retarded females with structurally abnormal X chromosomes that do not contain the X inactivation center. And fourth, dose-dependent overexpression of X-linked genes that normally "escape" X inactivation may account for the mental and developmental delay associated with increasing numbers of otherwise inactive X chromosomes in individuals with X chromosome aneuploidy.
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PMID:X chromosome inactivation and X-linked mental retardation. 882 43

Williams syndrome (WS) is characterized by distinct facial changes, growth deficiency, mental retardation, and congenital heart defect (particularly supravalvular aortic stenosis), associated at times with infantile hypercalcemia. Molecular genetic studies have indicated that hemizygosity at the elastin locus (7q11.23) causes WS. The purpose of this study was to confirm that this regional deletion, involving the elastin locus, is the cause of WS in Japan, and to clarify the correlation between the phenotype and the elastin locus. Thirty-two patients with WS and thirty of their relatives were examined by fluorescent in situ hybridization (FISH), using the WS chromosome region (WSCR) probe. All patients had cardiovascular disease (100%), 30 had typical WS facial changes (94%), 31 had mental retardation or developmental delay (97%), 16 were small-for-date at birth (50%), 14 had short stature (44%), and 13 had dental anomalies (41%). No relatives showed any manifestation of WS. Hemizygosity for a region of 7q11.23, involving the elastin locus, was found in all WS patients, but was not found in the 30 relatives.
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PMID:Molecular cytogenetic diagnosis of Williams syndrome. 886 24

Complex chromosome rearrangements (CCR) are rare structural rearrangements. Currently six cases of prenatally diagnosed balanced de novo CCR have been described. We present two new cases of prenatally ascertained balanced de novo CCR. In the first case, an amniocentesis revealed a balanced de novo three-way CCR involving chromosomes 5, 6, and 11 with a pericentric inversion of chromosome 5 [four breaks]. In the second case, a balanced de novo rearrangement was identified by amniocentesis which involved a reciprocal translocation between chromosomes 3 and 8 and a CCR involving chromosomes 6, 7, and 18 [six breaks]. The use of whole chromosome painting helped elucidate the nature of these rearrangements. A review of the postnatally ascertained cases suggests that most patients have congenital anomalies, minor anomalies, and/or developmental delay/mental retardation. In addition, there appears to be a relationship between the number of chromosome breaks and the extent of phenotypic effects. The paucity of information regarding prenatally diagnosed CCR and the bias of ascertainment of postnatal CCR cases poses a problem in counseling families.
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PMID:Prenatally diagnosed de novo apparently balanced complex chromosome rearrangements: two new cases and review of the literature. 886 25

We describe a 23-year-old woman with growth and mental retardation, hypoplasia of the nails and distal phalanges, particularly of the fifth fingers and toes, hirsutism, and a "coarse" face with large mouth and large tongue, and bushy eyebrows. Follow-up from birth to adulthood showed that developmental delay and hypoplasia of nails and distal phalanges are permanent signs. Sparse scalp hair, hypotonia, and feeding difficulties were present in early infancy. Later, growth retardation, hirsutism, and a "coarse" face with midface hypoplasia, broad nose, and large mouth became more impressive. Differential diagnosis includes a number of conditions, particularly Coffin-Siris syndrome, which is the most likely but not completely convincing diagnosis. Therefore, this woman might represent a variant of Coffin-Siris syndrome or a new entity.
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PMID:Variant of Coffin-Siris syndrome or previously undescribed syndrome? 887 Sep 24

To study the pathogenesis of central nervous system abnormalities in Down syndrome (DS), we have analyzed a new genetic model of DS, the partial trisomy 16 (Ts65Dn) mouse. Ts65Dn mice have an extra copy of the distal aspect of mouse chromosome 16, a segment homologous to human chromosome 21 that contains much of the genetic material responsible for the DS phenotype. Ts65Dn mice show developmental delay during the postnatal period as well as abnormal behaviors in both young and adult animals that may be analogous to mental retardation. Though the Ts65Dn brain is normal on gross examination, there is age-related degeneration of septohippocampal cholinergic neurons and astrocytic hypertrophy, markers of the Alzheimer disease pathology that is present in elderly DS individuals. These findings suggest that Ts65Dn mice may be used to study certain developmental and degenerative abnormalities in the DS brain.
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PMID:Developmental abnormalities and age-related neurodegeneration in a mouse model of Down syndrome. 891 91

Toriello-Carey syndrome is characterized by agenesis of the corpus callosum, telecanthus, short palpebral fissures, Robin sequence, abnormal ears, cardiac anomalies, and hypotonia. We describe two patients with Toriello-Carey syndrome and call attention to an unbalanced sex ratio. The first patient, a male, was born at term by Cesarean section and manifests micrognathia, cleft soft palate, hypoplastic right ear, anotia on the left side, cerebellar vermis hypoplasia, hydrocephalus, agenesis of the corpus callosum, and hypoplastic left heart. He died 2 days after birth. The second patient is the male sib of a patient reported previously [Am J Med Genet 42: 374-376; 1992]. He had large fontanelles, telecanthus, a short nose, small and malformed ears, micrognathia, a large ventricular septal defect, and pulmonary stenosis. At age 8 months he has growth retardation and developmental delay. A sister is unaffected. Review documented eight other patients with Toriello-Carey syndrome, six of whom were male. The two female patients are less severely affected and are still alive. Of the other male patients, all are deceased except one who is still alive at age 5 years; he has severe growth retardation (-3 SD), mental retardation (DQ44), severe speech delay, and characteristic anomalies. The predominance of affected males and the milder phenotype in the female patients suggests an X-linked gene or sex influenced gene.
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PMID:Toriello-Carey syndrome: evidence for X-linked inheritance. 1056 85

A full-term female neonate presented with facial port-wine stain, cutaneous telangiectasia, left facial hemihypertrophy, and left hemimegalencephaly at birth and subsequently developed hypertrophic change of left limb. She fit the diagnostic criteria of Klippel-Trenaunay-Weber syndrome. However, it was an unusual variant of this syndrome because the patient had left facial hemihypertrophy, left hemimegalencephaly and ipsilateral ventriculomegaly. Although patients with hemimegalencephaly are commonly thought to be associated with neurological defects, such as developmental delay, mental retardation and intractable seizure, she had normal neurological development and no seizure was detectable until two years of age.
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PMID:Klippel-Trenaunay-Weber syndrome with hemimegalencephaly: report of one case. 893 15

We report on a case of de novo direct duplication for the distal part of chromosome 3p: 46,XY,dir dup (3) (p25-->pter). At the age of 4 years and 7 months, the boy presented with moderate growth and mental retardation, muscular hypotonia, hypoplasia of the left kidney, a short neck, and a square-shaped face characterized by a broad and flat nasal bridge, slight epicanthus, and full cheeks. So far, only a few cases with such a small distal 3p duplication have been described, and none of them has a de novo direct duplication for this region. In our patient, dysmorphic signs are less impressive, and developmental delay is relatively moderate.
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PMID:De novo direct duplication 3 (p25-->pter): a previously undescribed chromosomal aberration. 893 69


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