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)

X-linked lissencephaly with absent corpus callosum and ambiguous genitalia is a newly recognized syndrome responsible for a severe neurological disorder of neonatal onset in boys. Based on the observations of 3 new cases, we confirm the phenotype in affected boys, describe additional MRI findings, report the neuropathological data, and show that carrier females may exhibit neurological and magnetic resonance imaging abnormalities. In affected boys, consistent clinical features of X-linked lissencephaly with absent corpus callosum and ambiguous genitalia are intractable epilepsy of neonatal onset, severe hypotonia, poor responsiveness, genital abnormalities, and early death. On magnetic resonance imaging, a gyration defect consisting of anterior pachygyria and posterior agyria with a moderately thickened brain cortex, dysplastic basal ganglia and complete agenesis of the corpus callosum are consistently found. Neuropathological examination of the brain shows a trilayered cortex containing exclusively pyramidal neurons, a neuronal migration defect, a disorganization of the basal ganglia, and gliotic and spongy white matter. Finally, females related to affected boys may have mental retardation and epilepsy, and they often display agenesis of the corpus callosum. These findings expand the phenotype of X-linked lissencephaly with absent corpus callosum and ambiguous genitalia, may help in the detection of carrier females in affected families, and give arguments for a semidominant X-linked mode of inheritance.
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PMID:X-linked lissencephaly with absent corpus callosum and ambiguous genitalia (XLAG): clinical, magnetic resonance imaging, and neuropathological findings. 1189 29

Coffin-Lowry syndrome (CLS) is an X-linked disorder associated with mental retardation, distinctive facies and hands, hypotonia, and skeletal abnormalities. The syndrome results from mutations in the RSK2 gene located in Xp22.2. Although the syndrome has been elucidated clinically, few, if any, studies have focused on the cognitive deficits of the affected males or carrier females. The subjects of the present study were selected from two African-American families who have the same missense mutation (C340T) in RSK2. The subjects included six affected males, seven carrier females, three normal males and three non-carrier (normal) females. Normal family members served as contrast/comparison cohorts to control for socio-economic, sociocultural and genetic variables which would impinge on intellectual abilities. Analysis of cognitive function, as measured by the Stanford-Binet Intelligence Scale, 4th edn, demonstrated a distinct hierarchy of abilities from normal to carrier to affected patients. The mean composite IQs of the cohorts were 90.8, 65.0 and 43.2 for normal, carrier and affected individuals, respectively. These findings lend support to the clinical concept of negative intellectual effects in carriers of certain X-linked mental retardation conditions. X-inactivation studies showed that carrier females had mild to significant skewing. Normal females in the family did not demonstrate skewing. The correlation coefficient between IQ and X-inactivation status among carriers was not significant.
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PMID:Cognitive function in Coffin-Lowry syndrome. 1203 Aug 96

Congenital adrenal hypoplasia (CAH) normally occurs in the neonatal period, with patients presenting with more or less severe salt-wasting syndrome. X-linked CAH has been associated with mutations in the DAX-1 gene, and boys have also been shown to have hypogonadotrophic hypogonadism. Recently, in three unrelated boys, CAH was associated with intrauterine growth retardation (IUGR), metaphyseal dysplasia and genital abnormalities, defining a new association called IMAGe. We now report four additional patients with this association, including the first living female. The four patients belong to two unrelated families (one brother and one sister from each family). These patients have the main clinical characteristics of IMAGe association: IUGR, facial dysmorphy (frontal bossing, broad nasal bridge, low-set ears), short limbs due to metaphyseal dysplasia, and adrenal insufficiency. As these patients are older than the initial three patients, we can also describe additional features: short adult height, normal puberty in boys as well as in the living girl. The boys have hypospadias associated with micropenis. The living girl came to clinical attention at the age of 5 years as a result of a familial survey, and careful questioning revealed that she had been suffering from mild adrenal insufficiency since early childhood. At least one boy has congenital hypotonia due to muscular dystrophy. In conclusion, these four new cases display familial transmission, strongly suggesting Mendelian autosomal recessive inheritance. Adrenal insufficiency may be mild. Hypotonia, described in all the patients, might be related to paucisymptomatic muscular dystrophy, as this condition is clearly heterogeneous varying with regard to severity, associated manifestations and outcome. If this symptom is part of the syndrome, which we cannot assume, it could help to localize the candidate gene.
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PMID:IMAGe association: additional clinical features and evidence for recessive autosomal inheritance. 1206 32

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in the MECP2 gene, with apparent lethality in male embryos. However, recent studies indicate that mutations in the MECP2 gene can cause congenital encephalopathy, an Angelman-like phenotype and even nonspecific mental retardation in males. We report on a 10-year-old boy with moderate mental retardation, hypotonia, obesity and gynaecomastia and a de novo 2-bp deletion in the MECP2 gene that resulted in a frameshift and premature stop codon. As some of the clinical features were suggestive of the Prader-Willi syndrome, it might be worthwhile screening for MECP2 mutations in patients with an atypical Prader-Willi phenotype but without the characteristic abnormalities on chromosome 15q. This report contributes to the phenotypic knowledge of male patients with MECP2 mutations. Moreover, this is the first reported male case of a de novo MECP2 mutation.
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PMID:De novo MECP2 frameshift mutation in a boy with moderate mental retardation, obesity and gynaecomastia. 1208 20

Mutations in the XNP gene have been reported in alpha thalassemia/mental retardation (MR) syndrome (ATR-X) and other severe X-linked MR conditions with facial dysmorphisms. In this report, we describe a missense mutation in exon 18 in a family with borderline to moderate MR. Like other disorders associated with an XNP mutation, skewed X-inactivation was found in all carrier females in this family. Only retrospective examination revealed childhood facial hypotonia and HbH inclusions in some of the affected males. These results expand the spectrum of clinical phenotypes known to be due to mutations in the XNP gene, and indicate that XNP mutation analysis should not be restricted to patients with severe MR and characteristic facial features.
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PMID:Expanding phenotype of XNP mutations: mild to moderate mental retardation. 1211 32

FG syndrome (OMIM 305450) is an X-linked condition comprising mental retardation, congenital hypotonia, constipation or anal malformations, and a distinctive appearance with disproportionately large head, tall and broad forehead, cowlicks and telecanthus. In a first linkage analysis carried out on 10 families, we demonstrated heterogeneity and assigned one gene [FGS1] to region Xq12-q21.31 [Briault et al., 1997: Am J Med Genet 73:87-90] corroborated by Graham et al. [1998: Am J Med Genet 80:145-156]. Heterogeneity was supported by the study of one family with apparent FG syndrome co-segregating with an inversion of X chromosome [inv(X)(q11q28)] ([FGS2], OMIM 300321) [Briault et al., 1999: Am J Med Genet 86:112-114 and Briault et al., 2000: Am J Med Genet 95:178-181]. We present the results of a new linkage analysis carried out on two families with FG syndrome. The two earlier known loci for FG syndrome, FGS1 and FGS2 (Xq11 or Xq28) were excluded by multipoint analysis of both families. Linkage was found, however, with locus DXS1060 suggesting that a third FG locus might be located at Xp22.3. In this region, two potential candidate genes, VCX-A and PRKX, were excluded by sequence analysis of the coding region in patients of the two reported FG families. The search for new candidate genes is in progress.
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PMID:FG syndrome: linkage analysis in two families supporting a new gene localization at Xp22.3 [FGS3]. 1223 12

Myotubularin is a ubiquitously expressed phosphatase that acts on phosphatidylinositol 3-monophosphate [PI(3)P], a lipid implicated in intracellular vesicle trafficking and autophagy. It is encoded by the MTM1 gene, which is mutated in X-linked myotubular myopathy (XLMTM), a muscular disorder characterized by generalized hypotonia and muscle weakness at birth leading to early death of most affected males. The disease was proposed to result from an arrest in myogenesis, as the skeletal muscle from patients contains hypotrophic fibers with centrally located nuclei that resemble fetal myotubes. To understand the physiopathological mechanism of XLMTM, we have generated mice lacking myotubularin by homologous recombination. These mice are viable, but their lifespan is severely reduced. They develop a generalized and progressive myopathy starting at around 4 weeks of age, with amyotrophy and accumulation of central nuclei in skeletal muscle fibers leading to death at 6-14 weeks. Contrary to expectations, we show that muscle differentiation in knockout mice occurs normally. We provide evidence that fibers with centralized myonuclei originate mainly from a structural maintenance defect affecting myotubularin-deficient muscle rather than a regenerative process. In addition, we demonstrate, through a conditional gene-targeting approach, that skeletal muscle is the primary target of murine XLMTM pathology. These mutant mice represent animal models for the human disease and will be a valuable tool for understanding the physiological role of myotubularin.
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PMID:The lipid phosphatase myotubularin is essential for skeletal muscle maintenance but not for myogenesis in mice. 1239 29

X-linked myotubular myopathy is a severe congenital myopathy in males, caused by mutations in the myotubularin (MTM1) gene on chromosome Xq28. In heterozygous carriers of MTM1 mutations, clinical symptoms are usually absent or only mild. We report a 6-year-old girl presenting at birth with marked hypotonia and associated feeding and respiratory difficulties. A muscle biopsy performed at 5 months suggested a diagnosis of myotubular myopathy. On examination at 6 years she had marked facial weakness with bilateral ptosis and external ophthalmoplegia, severe axial and proximal weakness and a mild scoliosis. Muscle magnetic resonance imaging showed a distinctive pattern of muscle involvement. Molecular genetic investigation of the MTM1 gene identified a heterozygous mutation in exon 12. X-inactivation studies in lymphocytes showed an extremely skewed pattern (97:3). This case emphasizes that investigation of the MTM1 gene and X-inactivation studies are indicated in isolated females with histopathological and clinical findings suggestive of myotubular myopathy.
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PMID:Early and severe presentation of X-linked myotubular myopathy in a girl with skewed X-inactivation. 1246 33

X-linked myotubular myopathy is a severe congenital myopathy that presents in the neonatal period with profound hypotonia and an inability to establish spontaneous respiration. Usually death occurs in infancy from respiratory failure. However, there is phenotypic variability; a number of affected boys have achieved respiratory independence and become ambulatory. Disease-causing mutations have been identified throughout the MTM1 gene on Xq28. MTM1 encodes the protein myotubularin, which is expressed ubiquitously. The main objectives of this study were to establish whether the nature or site of the mutation in the MTM1 gene could predict severity of the disease and to investigate whether early intensive clinical intervention facilitated survival until spontaneous improvement occurred. An association was demonstrated between the presence of a non-truncating mutation of the MTM1 gene and the mild phenotype. However, many non-truncating mutations were also seen in association with the severe phenotype and these were not confined to recognized functional domains of the protein. This suggests that the use of mutation analysis to predict prognosis in the early period following diagnosis is limited. Unexpectedly, over 50 patients surviving for more than 1 year were identified in this study. Further information obtained on 40 of these cases revealed that 50% were receiving 24-h ventilatory support, while 27% were ventilated at night only. The high survival rate for this disorder therefore reflects intensive medical intervention without which the majority of these boys would not survive.
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PMID:Genotype-phenotype correlations in X-linked myotubular myopathy. 1246 49

X-linked myotubular myopathy is a disorder characterized by severe neonatal hypotonia and respiratory insufficiency. The mutation of MTMI gene results in a defective production of myotubularin, which is responsible for the maturational arrest of muscle development. An identical mutation in the carrier mother and the diseased child establishes the inheritance. We report the disease in a neonate with a mutation on exon 6 of the MTMI gene. Surprisingly, the mother was healthy and did not carry this mutation, she is likely to have germline mosaicism.
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PMID:X-linked myotubular myopathy with probable germline mosaicism. 1248 75


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