Additional mitochondrial DNA mutations may explain extra-ocular involvement in LHON.
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Biomedical subjects
Publications and source records attributed to I F de Coo.
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BACKGROUND: Porencephaly (cystic cavities of the brain) is caused by perinatal vascular accidents from various causes. Several familial cases have been described and autosomal dominant inheritance linked to chromosome 13q has been suggested. COL4A1 is an essential component in basal membrane stability. Mouse mutants bearing an in-frame deletion of exon 40 of Col4a1 either die from haemorrhage in the perinatal period or have porencephaly in survivors. A report of inherited mutations in COL4A1 in two families has shown that familial porencephaly may have the same cause in humans. OBJECTIVE: To describe three novel COL4A1 mutations. RESULTS: The three mutations occurred in three unrelated Dutch families. There were two missense mutations of glycine residues predicted to result in abnormal collagen IV assembly, and one mutation predicted to abolish the traditional COL4A1 start codon. The last mutation was also present in an asymptomatic obligate carrier with white matter abnormalities on brain magnetic resonance imaging. CONCLUSIONS: This observation confirms COL4A1 as a major locus for genetic predisposition to perinatal cerebral haemorrhage and porencephaly and suggests variable expression of COL4A1 mutations.
Williams syndrome (WS) is a developmental disorder characterized by distinct facial features, congenital heart disease, mental retardation and a gregarious personality. The majority of people with this disorder have a submicroscopic deletion of genes in chromosome band 7q11.23. This deletion can be detected using fluorescence in situ hybridization (FISH). Although the condition is usually sporadic a few familial cases with autosomal dominant inheritance have been described. A clinical scoring system has been developed by Selicorni with which a diagnosis of 'Williams syndrome' can be made; in all patients in whom the diagnosis was made in this way FISH results were positive.
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BACKGROUND: Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive dysmyelinating disorder of the CNS. Duplications or point mutations in exons of the proteolipid protein (PLP) gene are found in most patients. OBJECTIVE: To describe five patients with PMD who have mutations in noncoding regions of the PLP gene. METHODS: Quantitative multiplex PCR and Southern blot analyses were used to detect duplication of the PLP gene, and DNA sequence analysis, including exon-intron borders, was used to detect mutation of the PLP gene. RESULTS: Duplication of the PLP gene was ruled out, and mutations were identified in noncoding regions of five patients in four families with PMD. In two brothers with a severe form of PMD, a G to T transversion at IVS6+3 was detected. This mutation resulted in skipping of exon 6 in the PLP mRNA of cultured fibroblasts. A patient who developed nystagmus at 16 months and progressive spastic ataxia at 18 months was found to have a 19-base pair (bp) deletion of a G-rich region near the 5' end of intron 3 of the PLP gene. A patient with a T to C transition at IVS3+2 and a patient with an A to G transition at IVS3+4 have the classic form of PMD. These, like the 19-bp deletion, are in intron 3, which is involved in PLP/DM20 alternative splice site selection. CONCLUSIONS: Mutations in introns of the PLP gene, even at positions that are not 100% conserved at splice sites, are an important cause of PMD.
We studied a patient with the diagnosis of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) for mitochondrial DNA mutations in muscle. Established MELAS mutations were excluded. Mitochondrial DNA was further analyzed for mutations in the 22 tRNA genes by single-strand conformation polymorphism (SSCP) analysis; a tRNA(Val) mutation (G1642A) was found. The structure of the altered tRNA, the heteroplasmy, and the absence of the mutation in the mother and in 100 control subjects suggests that the tRNA(Val) mutation is associated with the MELAS syndrome.
A survey was performed of magnetic resonance imaging (MRI) findings in 21 patients with congenital muscular dystrophy (CMD) with cerebral abnormalities to evaluate the contribution of MRI to the classification of CMD patients. In 5 patients with Walker-Warburg syndrome (WWS), MRI showed hydrocephalus due to aqueduct stenosis, generalized cerebral cortical agyric or pachygyric polymicrogyria, diffuse cerebral hemispheric white matter abnormalities, and malformations of posterior fossa structures. In 4 patients with muscle-eye-brain disease, MRI showed cortical dysplasia, but less severe than in WWS. The cerebral white matter either was normal or contained multiple focal abnormalities. Malformations of posterior fossa structures were present. Eight patients, classified as having classic merosin-deficient CMD (MD-CMD), had diffuse cerebral hemispheric white matter abnormalities, no other abnormalities. One patient with MD-CMD had only a few, focal white matter abnormalities. Three CMD patients had occipital agyria, otherwise normal gyration, multifocal or more diffuse cerebral white matter changes, and variable hypoplasia of pons and vermis. Two of the 3 patients had negative muscle merosin staining. The conclusion of the study is that MRI is an important adjunct in the classification of CMD patients. CMD with occipital agyria can be regarded as a newly recognized, separate CMD subtype.
Six children are presented with an isolated complex III deficiency in muscle tissue. More specifically, oxidation rates and ATP+CrP production rates from both pyruvate and succinate as substrates and/or the activity of decylubiquinol:cytochrome c oxidoreductase were all markedly reduced. Complex III deficiency was also present in liver of two patients tested, but could not be demonstrated in cultured fibroblasts of four patients tested. Mitochondrial DNA, extracted from muscle, was analyzed; no deletions or common point mutations were found. Four patients presented with a multi-organ disorder. Among these patients three presented at neonatal age with neurological signs and lactate elevation in blood and CSF, of whom two had severe neonatal Fanconi syndrome. One child, aged seven years, had encephalomyopathy, ophthalmoplegia, retinopathy and Wolff-Parkinson-White syndrome. The remaining two patients exhibited myopathy only, within the first year of life. Thus, like in other respiratory chain disorders, patients with complex III deficiency may present at any age and show variable symptoms and outcome, ranging from neonatal death to failure to thrive only. Apparently there are no clinical findings which are specific for complex III deficiency.
A mother and her son are reported who suffer from Leber's hereditary optic neuropathy (LHON) with the 11778 mtDNA mutation. In both subjects additional clinical and paraclinical evidence of a cerebral demyelinating disease was found. This combination has been reported incidentally in females, rarely in males. Magnetic resonance imaging and proton spectroscopy findings are reported. These findings are compatible with multiple sclerosis.
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Primary antiphospholipid syndrome or PAPS is characterised by antiphospholipid antibodies and arterial and/or venous thromboses. Numerous other clinical features have been shown to be related to this syndrome. Chorea is a well known but rare phenomenon in systemic lupus erythematosus; it has been shown to be strongly related to the presence of antiphospholipid antibodies. We describe two patients with chorea that appeared to be caused by the PAPS.
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Two brothers with 'pure' spastic paraplegia are presented. Inheritance of their condition probably was autosomal recessive. Clinical onset was in the first decade. Peripheral nerve conduction, visual and brain stem auditory evoked potentials were normal. Somatosensory evoked potentials suggested involvement of the cuneate tract. The relevance of neurophysiological evaluation in familial spastic paraplegia is discussed.
In this study we present a patient with Canavan disease or Van Bogaert and Bertrand type of spongiform leukodystrophy, proven by brain biopsy. We performed morphological studies and biochemical assays on fresh homogenates of the grey and white matter. Quantitative neuromorphological analysis of the cortex showed normal values except for poor dendritic arborization of the inner layers. No signs of neuronal damage were observed. The Na-K-ATPase activity was increased. Pyruvate and ketone bodies oxidation rates and the activity of cytochrome-c oxidase were normal. We conclude that there is neither a primary neuronal damage nor a primary mitochondrial dysfunction in the oxidative processes despite the abnormal morphology of mitochondria in this disease.