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PubMed2004

Microcephaly associated with abnormal gyral pattern.

Primary microcephaly is a heterogeneous group of cerebral malformations either with a relatively well-preserved or an abnormal gyral pattern. We describe the MRI findings and clinical features of 14 children with the combination of microcephaly and an abnormal gyral pattern. All children except one were Arabs and nine out of the 14 patients were born to consanguineous parents. Seven patients showed features of a simplified gyral pattern with relatively preserved posterior fossa structures. Two boys had a cortical malformation in the agyria-pachygyria spectrum; one of these two patients showed agenesis of the corpus callosum and severe cerebellar hypoplasia as well. The microcephaly was associated with polymicrogyria and leukoencephalopathy in two patients, with cortical dysplasia and hypogenesis of the corpus callosum in one patient, with agyria-pachygyria with callosal and pontocerebellar dysplasia in one patient, and a simplified gyral pattern with severe cerebellar hypoplasia in one case. One patient died in the neonatal period and three in infancy. All patients, who survived the neonatal period, had developmental delay, intellectual disability, and neurological deficits, and nine suffered from epilepsy.

Cerebral Cortex↗

PubMed1986

[Prenatal ultrasonic diagnosis of severe congenital microcephaly].

Antenatal ultrasound diagnosis of isolated microcephaly is difficult. Over and above this, other malformations must be safely excluded. Infants with congenital microcephaly are mentally and motorially severely retarded. Basing on two case reports with four microcephalic foetuses, the antenatal problems of sonographic diagnosis are explained. In all cases there was an isolated microcephaly without other malformations. Sonographic examination enabled early detection of three microcephalic foetuses between the 15th and 32nd week of gestation, and pregnancy could be terminated prematurely. Spontaneous delivery occurred in one pregnant woman at term; sonography had not been employed in this case.

Adult↗

PubMed2005

BRIT1/MCPH1 is a DNA damage responsive protein that regulates the Brca1-Chk1 pathway, implicating checkpoint dysfunction in microcephaly.

BRIT1 [BRCT-repeat inhibitor of hTERT expression], a repressor of human telomerase function, is implicated in cellular immortalization. Here, we find that BRIT1 acts as a regulator of both the intra-S and G2/M checkpoints. When BRIT1 expression is depleted, cells lose the ionizing radiation (IR)-induced cell cycle arrest and become IR sensitive. BRIT1 is a chromatin-associated protein that forms irradiation-induced nuclear foci that colocalize with gamma-H2AX foci. BRIT1 is also required for the expression of both BRCA1 and the checkpoint kinase Chk1 and phosphorylation of Nbs1. Thus, the checkpoint defects in the absence of BRIT1 are likely to result from its regulation of Nbs1, BRCA1, and Chk1. BRIT1 is identical to the recently discovered MCPH1 gene, found mutant in patients with primary microcephaly. The ataxia telangiectasia mutated-Rad3 related (ATR)-Chk1 pathway is defective in Seckel syndrome, another microcephaly disorder. We propose that the microcephaly observed in patients with MCPH1 deficiencies is due to disruption of the ATR-BRCA1-Chk1 signaling pathway that is also disrupted in Seckel syndrome patients.

BRCA1 Protein↗

PubMed1998

Primary autosomal recessive microcephaly (MCPH1) maps to chromosome 8p22-pter.

Primary (or "true") microcephaly is inherited as an autosomal recessive trait and is thought to be genetically heterogeneous. Using autozygosity mapping, we have identified a genetic locus (MCPH1) for primary microcephaly, at chromosome 8p22-pter, in two consanguineous families of Pakistani origin. Our results indicate that the gene lies within a 13-cM region between the markers D8S1824 and D8S1825 (maximum multipoint LOD score of 8.1 at D8S277). In addition, we have demonstrated the genetic heterogeneity of this condition by analyzing a total of nine consanguineous families with primary microcephaly.

Chromosome Mapping↗

PubMed2005

Autosomal recessive primary microcephaly (MCPH): a review of clinical, molecular, and evolutionary findings.

Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental disorder. It is characterized by two principal features, microcephaly present at birth and nonprogressive mental retardation. The microcephaly is the consequence of a small but architecturally normal brain, and it is the cerebral cortex that shows the greatest size reduction. There are at least seven MCPH loci, and four of the genes have been identified: MCPH1, encoding Microcephalin; MCPH3, encoding CDK5RAP2; MCPH5, encoding ASPM; and MCPH6, encoding CENPJ. These findings are starting to have an impact on the clinical management of families affected with MCPH. Present data suggest that MCPH is the consequence of deficient neurogenesis within the neurogenic epithelium. Evolutionary interest in MCPH has been sparked by the suggestion that changes in the MCPH genes might also be responsible for the increase in brain size during human evolution. Indeed, evolutionary analyses of Microcephalin and ASPM reveal evidence for positive selection during human and great ape evolution. So an understanding of this rare genetic disorder may offer us significant insights into neurogenic mitosis and the evolution of the most striking differences between us and our closest living relatives: brain size and cognitive ability.

Animals↗

PubMed1996

The microcephaly-lymphoedema syndrome: report of an additional family.

Fourteen patients from six families have been reported in which microcephaly occurs in conjunction with lymphoedema, with no evidence of mental retardation or serious neurological disabilities. Chorioretinal dysplasia was noted in a small number of affected individuals. Inheritance was either autosomal dominant or X-linked and the question has been raised whether all these cases represent one entity or separate syndromes. We report the 7th family with two affected sibs of different sex. Developmental testing revealed normal to borderline intelligence associated with Attention Deficit Hyperactivity Disorder. The suggested mode of inheritance in this family is autosomal recessive. X-linked dominant inheritance cannot be ruled out, however, since the male was more severely involved than the female. We concur with previous authors that the association of microcephaly and lymphoedema is a distinct genetic syndrome and we propose to name this entity the 'microcephaly-lymphoedema syndrome'.

Female↗

PubMed1987

Microcephaly: a review of genetic implications in its causation.

Microcephaly is a clinical sign rather than a nosological entity. It may even represent the extreme of normal variation. In pathological cases, it is always caused by an interruption of the neurobiologic processes of induction and cellular migration, or by a catastrophic insult to the central nervous system. The prime cause of this may be environmental or genetic. There is strong evidence for genetic heterogeneity, even among cases of 'true' or 'primary' microcephaly. Various taxonomies for the classification of microcephaly are discussed, taking into account environmental causation and various genetic mechanisms.

Environment↗

PubMed1986

Asymmetric crying facies with microcephaly and mental retardation. An autosomal dominant syndrome with variable expressivity.

An infant boy with asymmetric crying facies, microcephaly, developmental retardation and failure to thrive is reported. His two siblings died in the newborn period because of complex congenital heart defects. The mother and the maternal grandmother have asymmetric crying facies, microcephaly and normal intelligence. A maternal aunt has severe physical and mental retardation, facial asymmetry, microcephaly, and cleft palate. This family allows an expansion of the spectrum of malformations associated with asymmetric crying facies and suggests autosomal dominant inheritance with variable expressivity.

Abnormalities, Multiple↗

PubMed1995

Familial microcephaly with severe neurological deficits: a description of five affected siblings.

Autosomal recessive microcephaly is usually characterized by normal developmental milestones and minor neurological deficits. In this report, we describe five siblings in one family with marked microcephaly, intractable seizures, quadriplegia and profound mental retardation. The recurrence risk of microcephaly when associated with devastating neurological deficits, as exemplified by this family, may be high and in such cases, the role of appropriate genetic counseling is of utmost importance.

Child↗

PubMed2003

Evidence for a second gene for primary microcephaly at MCPH5 on chromosome 1.

Primary microcephaly has been mapped to five loci on different chromosomes. We present here the fine mapping of one of the loci, MCPH5, to a region of only 0.58 Mb located at the 1q31.3-1q32.1 junction. A genome scan was performed on five families from the Netherlands and Jordania, with 14 patients affected by microcephaly. A maximum LOD score of 4.78 was found for marker D1S1660 at the MCPH5 locus. Haplotype analysis suggests that the gene causing microcephaly is located between markers D1S3469 and D1S1660, which excludes the previously reported ASPM gene.

Animals↗

PubMed1996

Maternal hyperphenylalaninaemia as a cause of microcephaly and mental retardation.

We attempted to evaluate the role of maternal hyperphenylalaninaemia (HPA) as an isolated cause of mental retardation and microcephaly in children. This transversal study observed the plasma phenylalanine from mothers of 161 children with mental retardation and/or microcephaly of unknown origin. In this sample, we found two women with previously undiagnosed HPA, a frequency (2/161) higher than expected for our general population (1:12 500) (p < 0.001). We concluded that the plasma phenylalanine levels should be determined during preconceptional evaluation of every woman of reproductive age that already has had a child affected either by mental retardation or microcephaly of unknown cause. It is particularly significant where women currently having their pregnancies have not been screened for phenylketonuria as newborns, as happens in most developing countries.

Adult↗

PubMed1995

Severe microcephaly with normal intellectual development: the Nijmegen breakage syndrome.

A brother and sister are described with severe microcephaly of prenatal onset, normal intellectual and motor development, chromosomal breakage and cellular immunodeficiency, which is characteristic of the autosomal recessive condition, Nijmegen breakage syndrome. The proband was a girl who presented at 15 months, with normal developmental milestones and an extremely small head circumference of 36 cm. Twenty per cent of her lymphocytes showed spontaneous translocations involving chromosome 7p13, 7q35, 14q11, and 14q32. The lymphocytes also showed excessive x ray induced chromosome damage. She had T cell lymphopenia, but normal immunoglobulins, and a normal alpha fetoprotein. A brother was born shortly after her diagnosis was made. He also had extreme microcephaly of 28 cm, with similar spontaneous and x ray induced chromosomal breakage, and T cell lymphopenia. Neither child has clinical evidence of immunodeficiency. To test the hypothesis that Nijmegen breakage syndrome and ataxia telangiectasia are allelic disorders, haplotype analysis was carried out in the family using DNA markers spanning the AT locus on chromosome 11q22. The affected boy had a different haplotype from his affected sister. Thus in this family, the Nijmegen breakage syndrome is not allelic to the ataxia telangiectasia locus on chromosome 11q, and the two conditions are genetically distinct. The normal intellect in these children raises questions about normal brain development in the presence of severe microcephaly.

Ataxia Telangiectasia↗

PubMed1982

Yq- in a child with livedo reticularis, snub nose, microcephaly, and profound mental retardation.

A child with terminal deletion of the long arm of the Y chromosome (Yq--) presented with marked livedo reticularis, snub nose, microcephaly, short stature, and other dysmorphic features. He was profoundly mentally retarded. Most of the patients with Yq- have been reported as having varying dysmorphic features, mental retardation, and short stature. This child, in addition to the above, has livedo reticularis and microcephaly. He was of normal birthweight and, therefore, does not come into the syndrome of microcephaly, snub nose, livedo reticularis, and low birthweight dwarfism. Further information on Yq- should be obtained to ascertain if consistent patterns of abnormalities exist.

Body Height↗

PubMed1994

Microcephaly and congenital nephrotic syndrome owing to diffuse mesangial sclerosis: an autosomal recessive syndrome.

Three sibs born to consanguineous parents had congenital nephrotic syndrome, microcephaly, and psychomotor retardation. Pathology of the kidneys showed diffuse mesangial sclerosis with deposits of IgG and C3 in the mesangium and glomerular basement membranes. All three children died before the age of 3 years. Of 19 published cases of children with the association of congenital nephrotic syndrome and microcephaly, only four had histological evidence of diffuse mesangial sclerosis, and two of their sibs probably had the same disease. The association of nephrotic syndrome owing to congenital diffuse mesangial sclerosis, microcephaly, and mental retardation appears to be a distinct syndrome with an autosomal recessive mode of inheritance.

Abnormalities, Multiple↗

PubMedDate not supplied

Prenatally diagnosed microcephaly: a review of etiologies.

OBJECTIVE: To determine the incidence and etiology of prenatally diagnosed microcephaly. METHODS: Retrospective review of 10 years at a tertiary obstetrical hospital. The study population consisted of 21 infants with confirmed prenatal and postnatal microcephaly. RESULTS: There were 8 different definite/probable etiologies identified (viral, monochorionic twinning, genetic syndrome, neural tube defect, abnormal karyotype, hypoxic insult, constitutional). CONCLUSIONS: Retrospective study indicates the commonest etiologies for prenatal microcephaly are in utero infection, monochorionic twin insult, rare genetic syndrome and chromosomal anomalies.

Adult↗

PubMed1980

Ocular abnormalities of true microcephaly.

'True' microcephaly is associated with extremely varied ocular abnormalities, the most frequent being squint and optic atrophy. Within the heterogeneous group of the microcephalies it seems we can isolate a syndrome consisting of microcephaly, mental retardation, chorioretinal dysplasia and sometimes microphthalmia and embryological remnants such as persistence of the primary vitreous or persistence of its minor forms. Genetic transmission of such anomalies is generally considered to be autosomal recessive. The cases we are reporting on suggest that in some cases dominant transmission can be incriminated.

Adult↗

PubMed1999

Microcephaly-lymphedema-chorioretinal dysplasia: a unique genetic syndrome with variable expression and possible characteristic facial appearance.

We report on a follow-up examination of a family with microcephaly and lymphedema. The finding of chorioretinal dysplasia with variable visual deficit in multiple relatives, which was not previously discovered, supports the concept of microcephaly, lymphedema, and chorioretinopathy as being a single autosomal dominant genetic entity with variable expression. We recommend that fundoscopic examination be performed in all patients with microcephaly with or without lymphedema.

Adolescent↗

PubMed1989

An interesting case of extreme microcephaly.

The collections of the Museum in the Department of Anatomy, Faculty of Medicine, J. E. Purkynĕ University in Brno, include a skull of about 25 to 30-year-old individual with extreme microcephaly that has been so far described rarely in the morphological literature. The skull capacity is 355 cm3, which is only 26.1% of the skull capacity in a "normal" individual. While the facial skeleton is reduced only by 10-15% if compared with the norm, the cerebral part is striking by its extraordinarily small dimensions (smaller by 30-40% in comparison with the norm), particularly in the area of the frontal bone squama. The size of the skull is characterized best by the values of the basic metric measurements: maximal length of the skull 122 mm (norm: 172 mm), maximal breadth of the skull 94 mm (norm: 140 mm), height of the skull 96 mm (norm: 130 mm), circumference of the skull through the glabella 351 mm (norm: 510 mm). Foramen occipitale magnum is shifted strikingly to the dorsal direction. The cause of the microcephaly described cannot be explained explicitly just on the basis of the findings in the skull. For finding the actual cause a number of other data should be known. Authors' hypothesis that the problem is primary microcephaly has been supported even by roentgenological finding.

Adult↗