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)

A male infant, born from consanguineous parents, suffered from birth with a progressive neuromuscular disorder characterized by psychomotor delay, hypotonia, muscle weakness and wasting, deep-tendon areflexia and spastic posture. High levels of lactic acid in blood and cerebrospinal fluid suggested a mitochondrial respiratory chain defect. Muscle biopsy revealed ragged-red and cytochrome c oxidase-negative fibres, lipid accumulation and dystrophic changes. Multiple defects of respiratory complexes were detected in muscle homogenate, but cultured fibroblasts, myoblasts and myotubes were normal. Southern blot analysis showed markedly reduced levels of mitochondrial DNA (mtDNA) in muscle, while lymphocytes, fibroblasts and muscle precursor cells were normal. Neither depletion of mtDNA nor abnormalities of the respiratory complexes were observed in innervated muscle fibres cultured for as long as 4 months. No mutations were observed in two candidate nuclear genes, mtTFA and mtSSB, retro-transcribed, amplified and sequenced from the proband's mRNA. Sequence analysis of the mtDNA D-loop and of the origin of replication of the mtDNA light strand failed to identify potentially pathogenic mutations of these replicative elements in the proband's muscle mtDNA. Our findings indicate that mtDNA depletion is due to a nuclear encoded gene and suggest that the abnormality underlying defective mtDNA propagation must occur after muscle differentiation in vivo.
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PMID:Early-onset encephalomyopathy associated with tissue-specific mitochondrial DNA depletion: a morphological, biochemical and molecular-genetic study. 855 15

An infant with feeding difficulties, hypotonia, lactic acidemia, and severe hypoketotic hypoglycemia died at the age of 7 months of liver disease. Electron microscopy revealed abnormal mitochondria. Biochemical studies of mitochondrial enzymes in liver showed a decreased activity of complexes I, III, and IV. Mitochondrial DNA (mtDNA) content was reduced in liver 7% of the mean value in control subjects) and in muscle (50%). In kidney, brain, and heart, the mtDNA content was normal. The liver-specific mtDNA depletion syndrome in this patient manifested itself with features of both a respiratory chain defect and a mitochondrial fatty acid oxidation defect. Syndromes involving depletion of mtDNA can be diagnosed only when the activity of the respiratory chain enzymes and the content of mtDNA are investigated in the most affected tissues.
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PMID:Depletion of mitochondrial DNA in the liver of a patient with lactic acidemia and hypoketotic hypoglycemia. 862 28

Routine chromosomal analysis using GTG-banding alone showed a mosaic terminal deletion of 6q in a 14-week-old boy with developmental retardation, facial anomalies, agenesis of corpus callosum, cleft palate, hypotonia, short neck and pterygium colli, and minor anomalies of hands and feet. Discrepancies between the clinical findings on our patient and those described in the literature on patients having terminal deletions led to a more precise analysis of the karyotype. Reverse painting was performed on normal G-banded metaphases for exact determination of the breakpoints and on metaphases of the patient for evaluation of mosaicism. A DNA library that was obtained by microdissection of three deleted chromosomes 6 was used as a painting probe. Subsequent DNA amplification was performed with the help of topoisomerase-pretreated degenerate oligonucleotide primers. Unexpectedly, the hybridization pattern on normal metaphase chromosomes revealed an interstitial deletion with breakpoints at 6q25.1 and 6q27 instead of a terminal deletion. Hybridization on metaphases of the patient showed one deleted chromosome 6 in all metaphases analyzed at a higher resolution rather than mosaicism as previously assumed [karyotype, 46,XY,del(6)(q25.1 --> q27)]. We assume that in the single cases of 6q- described in the literature the deletions are misclassified. This might be due to difficulties in distinguishing between interstitial and terminal deletions at 6q and in precisely defining chromosomal breakpoints after GTG-banding alone.
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PMID:Interstitial deletion of chromosome 6q: precise definition of the breakpoints by microdissection, DNA amplification, and reverse painting. 864 83

X-linked myotubular myopathy (MTM1) is a severe congenital myopathy characterized by hypotonia, muscle weakness, and associated respiratory insufficiency. Perinatal death is common. The disease locus was shown to be linked to polymorphic markers in Xq28 and we have recently refined the MTM1 locus to a physical region of less than one megabase (Mb) at proximal Xq28. Two new microsatellite markers were developed and assigned in the MTM1 candidate region. We applied them and other DNA markers for prenatal diagnosis in two families. In one case, an affected fetus was predicted and a recombination event was observed with two more distal markers in the region. The second fetus was born unaffected as predicted. The new DNA markers and the precise location of the MTM1 gene provide an improvement for early prenatal diagnosis of the disease. We present suggestions for different combinations of linked and flanking DNA markers for maximal informativeness and accuracy.
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PMID:Prenatal diagnosis of X-linked myotubular myopathy: strategies using new and tightly linked DNA markers. 871 Jul 76

Two unpublished cases with partial tandem duplication of 12p and one previously published case were studied by fluorescence in situ hybridization using 11 cosmid DNA probes from 12p. We propose that the smallest duplications of 12(p13.2pter) and 12(p13.1p13.33) produce the "trisomy 12p syndrome" which is characterized by heavy birth weight, macrocephaly, muscular hypotonia, short neck, flat face, high forehead, prominent cheeks, large philtrum, short nose with anteverted nostrils, and broad everted lower lip. From a review of the published cases we conclude that gross malformations are lacking in "pure" trisomy 12p, and mental retardation is severe in complete and moderate in partial trisomy 12p. Polydactyly and accessory nipples were found only with almost complete trisomy 12p. Abnormalities of hair growth may be related to a gene at 12p. The sub-band 12p11.21 may be critical for acrocallosal syndrome. Macrocephaly may be due to a metabolic disorder.
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PMID:Clinical and molecular cytogenetic observations in three cases of "trisomy 12p syndrome". 872 17

Mitochondrial DNA depletion is a quantitative disorder of mtDNA, characterized by tissue-specific reductions in mtDNA copy number, that presents in infancy or early childhood. It is most likely transmitted as an autosomal recessive trait, although about half of the described cases are sporadic. To estimate its prevalence we measured relative mtDNA copy number (mtDNA: 18S rDNA ratio) by Southern blot analysis in muscle biopsy samples from all children with compatible histories referred between 1983 and 1994. Of the 304 biopsies evaluated, 54 met the study criteria. We found 6 patients (2 male, 4 female) with mtDNA depletion (relative mtDNA copy number 7.9-33.2% of control). Their clinical course and findings were heterogeneous, however all but one manifested weakness, hypotonia, and developmental delay. Clinical severity was not obviously related to the degree of mtDNA depletion. No patient had ragged-red fibers, although 2 had a lipid storage myopathy. Immunofluorescence with antibodies to double-stranded DNA, COX IV, and COX II demonstrated homogeneously reduced reactivity to all three antibodies compared with control. mtDNA depletion may be a relatively common neurogenetic disorder of infancy and early childhood and should be considered in children with unexplained weakness, hypotonia, or developmental delay.
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PMID:Mitochondrial DNA depletion: prevalence in a pediatric population referred for neurologic evaluation. 873 3

We describe an infant girl who presented at age 4 1/2 months with developmental delay, infantile spasms, hypotonia, and elevated lactate levels in the blood and cerebrospinal fluid. She had minor dysmorphic features. Muscle phosphorus magnetic resonance spectroscopy demonstrated reduced phosphocreatine and increased inorganic phosphate, suggesting a defect in oxidative energy metabolism. Pyruvate dehydrogenase activity in cultured fibroblasts was reduced (0.35 nmol/mg mitochondrial protein/min; controls 0.7-1.1 nmol/mg mitochondrial protein/min). Immunoblotting demonstrated a reduced amount of pyruvate dehydrogenase (PDH) E1 alpha immunoreactive protein with normal amounts of E2 protein. Single-strand conformational polymorphism analysis of E1 alpha cDNA prepared from fibroblasts disclosed an abnormal migration pattern, suggesting heterozygosity for a mutant allele. Dideoxy-fingerprinting of PCR-amplified genomic DNA was used to localize the mutation to exon 10. Direct sequencing demonstrated a novel 13-bp insertion mutation that would lead to premature termination of the protein product. This study further extends the allelic heterogeneity underlying PDH deficiency. The demonstration of bioenergetic abnormalities in muscle emphasizes that hypotonia in PDH deficiency may have combined peripheral and central etiologies. The results further suggest that the association of cerebral dysgenesis with lactic acidemia in females may be a useful clue to PDH deficiency.
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PMID:Association of cerebral dysgenesis and lactic acidemia with X-linked PDH E1 alpha subunit mutations in females. 877 Nov 69

Trinucleotide repeat expansion in the Machado-Joseph disease (MJD) gene has been found in 26 patients from 20 unrelated Japanese families. Expanded alleles had 68 to 84 repeats, whereas normal alleles had 14 to 37 repeats. The age of onset was inversely correlated with the repeat length. To evaluate in detail the relationship between the repeat length and clinical features, we subdivided the 26 patients into three groups on the basis of the repeat length (group 1, 78 repeats or more; group 2, 74 to 77 repeats; group 3, 73 repeats or less). Group 1 and group 2 had common features of spasticity, hyperreflexia, Babinski sign, bulging eyes, facial myokymia and extrapyramidal signs as well as cerebellar ataxia and ophthalmoplegia. It should be noted that group 1 showed more prominent pyramidal and extrapyramidal signs than group 2. In contrast, group 3 showed hypotonia, hyporeflexia and sensory disturbance in addition to cerebellar ataxia and ophthalmoplegia. These findings suggest that the repeat length plays an important role in phenotypic variation. DNA analysis for the MJD mutation was clearly useful for making an accurate diagnosis in patients without bulging eyes, facial myokymia, dystonia or marked spasticity.
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PMID:The relationship between trinucleotide repeat length and phenotypic variation in Machado-Joseph disease. 883 72

A girl carrying a de novo balanced 13-14 robertsonian translocation showed a clinical phenotype with severe hypotonia, hyperextensible joints, frontal bossing, asymmetric face, no mental retardation, severe scoliosis and motor delay. In situ hybridization analysis on chromosome spreads revealed the presence of the two centromeres in the rearranged chromosomes. Molecular analysis on genomic DNA showed the presence in the proposita of two chromosomes 14 of maternal origin and no chromosome 14 from the father indicating a maternal monocentric uniparental disomy for chromosome 14 (mUPD14). Our patient shows several similarities with other reported cases of mUPD14, suggesting imprinting of a region(s) of chromosome 14 and defining a possible mUPD14 Syndrome.
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PMID:Maternal uniparental disomy for chromosome 14. 887 27

X-linked recessive myotubular myopathy (XLMTM) is a severe neonatal neuro-muscular disease characterized by muscle weakness, hypotonia, and respiratory problems. The locus for the XLMTM gene (MTM1) has previously been mapped to Xq28 between the markers DXS304 and DXS497 by linkage analyses and by determining the breakpoints of deletion patients. We report linkage analysis data or 20 XLMTM families who were tested using the DNA markers DXS1113, DXS304, DXS455, DXS1684, DXS305 and DXS52 and present two families showing recombination between MTM1 and either DXS304, DXS334 or DXS305. We found each of the families to be informative for at least three markers. Based on these findings we excluded 30 women from being carriers, the carrier status of 17 obligate carrier mothers could be confirmed and eight mothers and sisters were identified as to be at high risk of carrying a MTM1 mutation. By combining recently published data with the results of our recombinant families, we suggest that the MTM1 locus maps between DXS334 and DXS497 narrowing the region of interest from 600 kb to an estimated < 500 kb interval. This additional refinement in the localization of MTM1 means a further step towards the isolation of the gene in the near future, and allows more reliable and efficient carrier detection and prenatal diagnosis.
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PMID:X-linked myotubular myopathy: refinement of the critical gene region. 888 57


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