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

Feingold syndrome type 1: a rare cause of fetal microcephaly (prenatal diagnosis)

We report a case of fetal microcephaly found during the second trimester ultrasound and confirmed by further ultrasound scans and fetal MRI. The array comparative genomic hybridisation analysis of the fetus and the male parent showed a 1.5 Mb deletion overlapping the Feingold syndrome region, an autosomal dominant syndrome that can cause microcephaly, facial/hand abnormalities, mild neurodevelopmental delay and others. This case illustrates the need for a detailed investigation by a multidisciplinary team to provide prenatal counselling regarding a postnatal outcome to the parents and orient their decision towards the continuation or termination of pregnancy.

Loss of function of PCDH12 underlies recessive microcephaly mimicking intrauterine infection

OBJECTIVE

To identify the genetic basis of a recessive syndrome characterized by prenatal hyperechogenic brain foci, congenital microcephaly, hypothalamic midbrain dysplasia, epilepsy, and profound global developmental disability.

METHODS

Identification of the responsible gene by whole exome sequencing and homozygosity mapping.

RESULTS

Ten patients from 4 consanguineous Palestinian families manifested in utero with hyperechogenic brain foci, microcephaly, and intrauterine growth retardation. Postnatally, patients had progressive severe microcephaly, neonatal seizures, and virtually no developmental milestones. Brain imaging revealed dysplastic elongated masses in the midbrain-hypothalamus-optic tract area. Whole exome sequencing of one affected child revealed only PCDH12 c.2515C>T, p.R839X, to be homozygous in the proband and to cosegregate with the condition in her family. The allele frequency of PCDH12 p.R839X is <0.00001 worldwide. Genotyping PCDH12 p.R839X in 3 other families with affected children yielded perfect cosegregation with the phenotype (probability by chance is 2.0 × 10(-12)). Homozygosity mapping revealed that PCDH12 p.R839X lies in the largest homozygous region (11.7 MB) shared by all affected patients. The mutation reduces transcript expression by 84% (p < 2.4 × 10(-13)). PCDH12 is a vascular endothelial protocadherin that promotes cellular adhesion. Endothelial adhesion disruptions due to mutations in OCLN or JAM3 also cause congenital microcephaly, intracranial calcifications, and profound psychomotor disability.

CONCLUSIONS

Loss of function of PCDH12 leads to recessive congenital microcephaly with profound developmental disability. The phenotype resembles Aicardi-Goutières syndrome and in utero infections. In cases with similar manifestations but no evidence of infection, our results suggest consideration of an additional, albeit rare, cause of congenital microcephaly.

Methodologic issues in epidemiologic studies of congenital microcephaly

In this methodological paper, we explore a number of issues that pose problems for those who seek the antecedents of congenital microcephaly. We pay particular attention to three concerns: Who is a case? How should cases be classified? To whom should cases be compared?

Anthropometric craniofacial pattern profiles in microcephaly

Craniofacial measurements were taken in 60 cases presenting with microcephaly. The cases were classified etiologically and morphologically and the latter was further subclassified. Craniofacial pattern profiles, cranial capacity, and the pattern variability index were calculated and compared with normal Hungarian controls of the same age and sex. In addition, correlation analysis between cranial capacity and IQ was done. Our results show significant similarity of the craniofacial pattern profiles between isolated microcephaly (IMC) and multiple microcephaly (MMC), and between primary microcephaly (PMC) and secondary microcephaly (SMC). The pattern variability index of the microcephalic cases was 4.77. There was no correlation between cranial capacity and IQ in the microcephalic patients.

Molecular basis of autosomal recessive diseases among the Palestinian Arabs

In the review of the literature, 71 different autosomal recessive diseases have been delineated that are relatively frequent among Palestinian Arabs. Among those, in 40 the mutation(s) responsible for the diseases are known. Fourteen of these disorders were caused by a single mutation, while the other 26 were due to multiple mutations. Most of the mutations were found in homozygosity among the affected patients. It is probable that the high frequency of most of the genetic diseases among the Palestinian Arabs is due to a founder effect as the result of the high consanguinity rates in this population. However, in some cases the high frequency was demonstrated to be secondary to the presence of multiple mutations, either allelic or in different genes in a small geographic region. This phenomenon remains unexplained but may be secondary to a selective advantage to the carriers, either specific to the region or to the population.

Characterization of seizures in the flathead rat: a new genetic model of epilepsy in early postnatal development

PURPOSE

Disorders in normal central nervous system (CNS) development are often associated with epilepsy. This report characterizes seizures in a novel genetic model of developmental epilepsy, the Flathead (FH) rat.

METHODS

Animals (n = 76) ages P0-22 were monitored for clinical and electrographic seizure activity. The effects of various AEDs on seizure frequency and duration also were assessed: phenobarbital (PB; 40 mg/kg), valproate (VPA; 400 mg/kg), or ethosuximide (ESM; 600 mg/kg).

RESULTS

FHs display episodes of behavior characterized by whole-body tremor, strub tail, alternating forelimb clonus, and complete tonus. EEG recordings from neocortex reveal that FH seizures are bilateral and begin around P7. Seizures occur at a frequency of approximately six per hour from P7 to P18 and the average duration of seizures increases through development. PB, VPA, and ESM failed to prevent seizures; however, PB significantly increased the interval of seizures but had no effects on the duration of seizures, whereas VPA decreased the duration of seizures and not the interval.

CONCLUSIONS

Seizures in FH rats occur at a constant and high frequency through a defined period in early postnatal development, and these seizures are not completely blocked by high doses of PB, VPA, or ESM. Because FH is a single-locus mutant displaying a highly regular pattern of seizure activity, it is an ideal model for examining the process of epileptogenesis in the developing brain, evaluating new AED therapies, and determining the identity of a gene essential to the normal development of cortical excitability.

Autosomal recessive microcephaly with neonatal myoclonic seizures: clinical and MRI findings

We describe an infant who was born to a consanguineous couple of Palestinian origin. The patient had severe microcephaly, myoclonic seizures, hypsarrythmia, spasticity, hypertonicity, and profound mental retardation. A similar case was reported in another unrelated Palestinian family, suggesting that this condition may be endemic. The condition resembles early onset myoclonic seizures and spasticity described by Tolmie et al.: Am J Med Genet 27:583-594 [1987]. To the best of our knowledge, only four pairs of sibs have been described with this syndrome; however, to date no magnetic resonance imaging (MRI) findings were reported for this condition. We present the clinical and radiological findings in the patients, including the first report of MRI findings.

3-Phosphoglycerate dehydrogenase deficiency: an inborn error of serine biosynthesis

Serine concentrations were markedly decreased in the cerebrospinal fluid of two brothers with congenital microcephaly, profound psychomotor retardation, hypertonia, epilepsy, growth retardation, and hypogonadism. The youngest boy also had congenital bilateral cataract. Magnetic resonance imaging of the brain showed evidence of dysmyelination. Plasma serine as well as plasma and cerebrospinal fluid glycine concentrations were also decreased but to a lesser extent. Treatment with oral serine in the youngest patient significantly increased cerebrospinal fluid serine and abolished the convulsions. In fibroblasts of both patients, a decreased activity was demonstrated of 3-phosphoglycerate dehydrogenase, the first step of serine biosynthesis (22% and 13% of the mean control value). This is an unusual disorder as the great majority of aminoacidopathies are catabolic defects. It is a severe but potentially treatable inborn error of metabolism that has not been previously reported in man.