Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026827 (hypotonia)
 5,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Distal Xq disomy in males results in characteristic phenotypes that typically include mental retardation, microcephaly, prominent hypotonia and hypogonadism. The 8-year-old male patient reported here presented with mental retardation, prominent ears, abnormally wide and unstable gait and flat occiput. He did not have microcephaly or hypogonadism. Subtelomeric multi-fluorescence in-situ hybridization analysis identified a duplicated terminal portion of chromosome Xq/Yq located distally on Yp. Further analysis of the duplicated region using additional FISH probes, specific for the distal Xq and Yp chromosomal regions, and array comparative genomic hybridization analysis using the 244 K oligo-array of Agilent, showed that it spans approximately 2.15 Mb of the terminal Xq region and includes MECP2 but not L1CAM gene. This is the smallest well-characterized terminal Xq duplication reported to date. Genes proximal to MECP2 that are not duplicated in our patient are likely responsible for additional clinical manifestations including characteristic facial dysmorphic features, microcephaly, hypogonadism and more severe hypotonia, as noted in patients with larger distal Xq duplications. Our patient's features are similar to previously reported MECP2 gene duplication cases, thus suggesting minor or no contribution of duplicated genes distal of MECP2 to the reported phenotype.
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PMID:De-novo 2.15 Mb terminal Xq duplication involving MECP2 but not L1CAM gene in a male patient with mental retardation. 1909 26

Distal Xq duplications refer to chromosomal disorders resulting from involvement of the long arm of the X chromosome (Xq). Clinical manifestations widely vary depending on the gender of the patient and on the gene content of the duplicated segment. Prevalence of Xq duplications remains unknown. About 40 cases of Xq28 functional disomy due to cytogenetically visible rearrangements, and about 50 cases of cryptic duplications encompassing the MECP2 gene have been reported. The most frequently reported distal duplications involve the Xq28 segment and yield a recognisable phenotype including distinctive facial features (premature closure of the fontanels or ridged metopic suture, broad face with full cheeks, epicanthal folds, large ears, small and open mouth, ear anomalies, pointed nose, abnormal palate and facial hypotonia), major axial hypotonia, severe developmental delay, severe feeding difficulties, abnormal genitalia and proneness to infections. Xq duplications may be caused either by an intrachromosomal duplication or an unbalanced X/Y or X/autosome translocation. In XY males, structural X disomy always results in functional disomy. In females, failure of X chromosome dosage compensation could result from a variety of mechanisms, including an unfavourable pattern of inactivation, a breakpoint separating an X segment from the X-inactivation centre in cis, or a small ring chromosome. The MECP2 gene in Xq28 is the most important dosage-sensitive gene responsible for the abnormal phenotype in duplications of distal Xq. Diagnosis is based on clinical features and is confirmed by CGH array techniques. Differential diagnoses include Prader-Willi syndrome and Alpha thalassaemia-mental retardation, X linked (ATR-X). The recurrence risk is significant if a structural rearrangement is present in one of the parent, the most frequent situation being that of an intrachromosomal duplication inherited from the mother. Prenatal diagnosis is performed by cytogenetic testing including FISH and/or DNA quantification methods. Management is multi-specialist and only symptomatic, with special attention to prevention of malnutrition and recurrent infections. Educational and rehabilitation support should be offered to all patients.
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PMID:Distal Xq duplication and functional Xq disomy. 1923 94

The Forkhead box G1 (FOXG1) is a transcription factor that is critical for forebrain development, where it promotes progenitor proliferation and suppresses premature neurogenesis. Recently, the FOXG1 gene was implicated in the molecular aetiology of the congenital variant of Rett syndrome. So far, 15 FOXG1 molecular alterations, including only eight point mutations, have been reported. We screened the FOXG1 gene in a cohort of 206 MECP2 and CDKL5 mutation negative patients (136 females and 70 males) with severe encephalopathy and microcephaly. The screening was negative in all males, but two de novo mutations (c.1248C>G, p.Y416X and c.460_461dupG, p.E154GfsX300) were identified in two unrelated girls. Both patients showed neurological symptoms from the neonatal period with poor reactivity, hypotonia, and severe microcephaly. During the first year of life, both patients had feeding difficulties and made slow developmental progress. At 5 years old, the girls were significantly neurologically impaired with gross hypotonia, no language, convergent strabismus, and no voluntary hand use. Moreover, they presented a combination of jerky movements, hand-mouthing, and hand-washing stereotypies. Hence, FOXG1 mutation patients demonstrate severe encephalopathy compatible with the congenital variant, as well as additional features such as absent eye contact, inconsolable crying during the perinatal period, and delayed myelination with thin to hypoplastic corpus callosum. Although the overall frequency of mutations in FOXG1 in females with severe mental retardation and microcephaly appears to be low (1.5%), our findings suggest the requirement to investigate both point mutations and gene dosage in the FOXG1 gene in patients with severe encephalopathy with microcephaly and some Rett-like features.
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PMID:Revisiting the phenotype associated with FOXG1 mutations: two novel cases of congenital Rett variant. 1980 73

Localised duplications, involving the MECP2 locus, at Xq28 have been associated with a syndrome comprising X-linked mental retardation, hypotonia and recurrent infections in males. We now present neuroradiological evidence that progressive cerebellar degenerative changes may also be a consistent feature of this syndrome, emerging in the second decade of life. We report seven affected males, from three different families who, in addition to the previously described clinical findings, have a reduction in the volume of the white matter and mild dilatation of the lateral ventricles. Three of the older patients show a consistent cerebellar degenerative phenotype. Furthermore, we describe the first female affected with the disorder. The female was mildly affected and shows X-inactivation in the ratio of 70:30, demonstrating that X-inactivation cannot be exclusively relied upon to spare the female carriers from symptoms. In conclusion, there is a radiological phenotype associated with Xq28 duplication which clearly demonstrates progressive degenerative cerebellar disease as part of the syndrome.
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PMID:Progressive cerebellar degenerative changes in the severe mental retardation syndrome caused by duplication of MECP2 and adjacent loci on Xq28. 2017 1

In this review, we detail the history, molecular diagnosis, epidemiology, and clinical features of the MECP2 duplication syndrome, including considerations for the care of patients with this X-linked neurodevelopmental disorder. MECP2 duplication syndrome is 100% penetrant in affected males and is associated with infantile hypotonia, severe to profound mental retardation, autism or autistic features, poor speech development, recurrent infections, epilepsy, progressive spasticity, and, in some cases, developmental regression. Most of the reported cases are inherited, however, de novo cases have been documented. While carrier females have been reported to be unaffected, more recent research demonstrates that despite normal intelligence, female carriers display a range of neuropsychiatric phenotypes that pre-date the birth of an affected son. Given what we know of the syndrome to date, we propose that genetic testing is warranted in cases of males with infantile hypotonia and in cases of boys with mental retardation and autistic features with or without recurrent infections, progressive spasticity, epilepsy, or developmental regression. We discuss recommendations for clinical management and surveillance as well as the need for further clinical, genotype-phenotype, and molecular studies to assist the patients and their families who are affected by this syndrome.
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PMID:The MECP2 duplication syndrome. 2042 14

The etiology of mental retardation remains elusive in the majority of cases. Microdeletions within chromosomal bands 5q14.3q15 were recently identified as a recurrent cause of severe mental retardation, epilepsy, muscular hypotonia, and variable minor anomalies. By molecular karyotyping we identified two novel 2.4- and 1.5-Mb microdeletions of this region in patients with a similar phenotype. Both deletions contained the MEF2C gene, which is located proximally to the previously defined smallest region of overlap. Nevertheless, due to its known role in neurogenesis, we considered MEF2C as a phenocritical candidate gene for the 5q14.3q15 microdeletion phenotype. We therefore performed mutational analysis in 362 patients with severe mental retardation and found two truncating and two missense de novo mutations in MEF2C, establishing defects in this transcription factor as a novel relatively frequent autosomal dominant cause of severe mental retardation accounting for as much as 1.1% of patients. In these patients we found diminished MECP2 and CDKL5 expression in vivo, and transcriptional reporter assays indicated that MEF2C mutations diminish synergistic transactivation of E-box promoters including that of MECP2 and CDKL5. We therefore conclude that the phenotypic overlap of patients with MEF2C mutations and atypical Rett syndrome is due to the involvement of a common pathway.
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PMID:Mutations in MEF2C from the 5q14.3q15 microdeletion syndrome region are a frequent cause of severe mental retardation and diminish MECP2 and CDKL5 expression. 2051 42

Duplications of the Xq28 chromosome region resulting in functional disomy are associated with a distinct clinical phenotype characterized by infantile hypotonia, severe developmental delay, progressive neurological impairment, absent speech, and proneness to infections. Increased expression of the dosage-sensitive MECP2 gene is considered responsible for the severe neurological impairments observed in affected individuals. Although cytogenetically visible duplications of Xq28 are well documented in the published literature, recent advances using array comparative genomic hybridization (CGH) led to the detection of an increasing number of microduplications spanning MECP2. In rare cases, duplication results from intrachromosomal rearrangement between the X and Y chromosomes. We report six cases with sex chromosome rearrangements involving duplication of MECP2. Cases 1-4 are unbalanced rearrangements between X and Y, resulting in MECP2 duplication. The additional Xq material was translocated to Yp in three cases (cases 1-3), and to the heterochromatic region of Yq12 in one case (case 4). Cases 5 and 6 were identified by array CGH to have a loss in copy number at Xp and a gain in copy number at Xq28 involving the MECP2 gene. In both cases, fluorescent in situ hybridization (FISH) analysis revealed a recombinant X chromosome containing the duplicated material from Xq28 on Xp, resulting from a maternal pericentric inversion. These cases add to a growing number of MECP2 duplications that have been detected by array CGH, while demonstrating the value of confirmatory chromosome and FISH studies for the localization of the duplicated material and the identification of complex rearrangements.
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PMID:MECP2 duplications in six patients with complex sex chromosome rearrangements. 2111 12

Chromosome X-to-autosome translocations [t(X;A)] are rare rearrangements with an estimated occurrence of 1 to 3 per 10,000 live births. Occurrences of Xq duplications have been observed in male and female subjects in whom the X chromosome segment escapes inactivation and results in functional disomy. We report a case of X;6 translocation in a 7-year-old boy with severe mental retardation, hypotonia, and recurrent respiratory tract infections. High-resolution chromosome analyses (fluorescence in situ hybridization, multiplex ligation probe-dependent amplification, and whole-genome array) revealed a terminal duplication of chromosome X at q28-qter (approximately 3.246 Mb in size) involving gene MECP2 and a terminal deletion (approximately 1.89 Mb) with the breakpoint at 6q27. This is the second report of a boy with a cryptic unbalanced Xq-autosome translocation. This case increases our understanding of mental disability caused by terminal Xq duplication.
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PMID:Cryptic x; autosome translocation in a boy--delineation of the phenotype. 2131 Mar 40

Xq28 duplications including MECP2 are a well-known cause of severe mental retardation in males with seizures, muscular hypotonia, progressive spasticity, poor speech and recurrent infections that often lead to early death. Female carriers usually show a normal intellectual performance due to skewed X-inactivation (XCI). We report on two female patients with a de novo MECP2 duplication associated with moderate mental retardation. In both patients, the de novo duplication occurred on the paternal allele, and both patients show a random XCI, which can be assumed as the triggering factor for the phenotype. Furthermore, we describe the phenotype that might be restricted to unspecific mild-to -moderate mental retardation with neurological features in early adulthood.
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PMID:De novo MECP2 duplication in two females with random X-inactivation and moderate mental retardation. 2132 85

We describe two patients with severe developmental delay, hypotonia and breathing abnormalities initially diagnosed with the autosomal recessive Joubert syndrome (JBS) who at a later stage appeared to carry chromosomal abnormalities. One case was due to a 4.8 Mb terminal 1q44 deletion, and the other due to a 15.5 Mb duplication of Xq27.2-qter containing the MECP2 gene. Critical evaluation of the clinical data showed that, retrospectively, the cases did not fulfil the diagnostic criteria for JBS, and that the diagnosis of JBS was incorrectly made. We discuss the diagnostic pitfalls and recommend adhering strictly to the JBS diagnostic criteria in the case of a negative molecular diagnosis. Critical assessment of the MRI findings by a specialized neuroradiologist is imperative. As chromosomal abnormalities may give rise to symptoms resembling JBS, we recommend array-based screening for segmental aneuploidies as an initial genetic test in all cases with a JBS-like phenotype.
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PMID:Chromosomal abnormalities resembling Joubert syndrome: two cases illustrating the diagnostic pitfalls. 2152 49


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