Despite undisputable benefits, midtrimester prenatal surgery is not a cure for myelomeningocele (MMC): residual intracranial and motor deficits leading to lifelong handicap question the timing of ...prenatal surgery. Indeed, the timing and intensity of intrauterine spinal cord injury remains ill defined.
We aimed to describe the natural history of neuronal loss in MMC in utero based on postmortem pathology.
Pathology findings were analyzed in 186 cases of myelomeningocele with lesion level between S1 and T1. Using a case-control, cross-sectional design, we investigated the timewise progression and topographic extension of neuronal loss between 13 and 39 weeks. Motor neurons were counted on histology at several spinal levels in 54 isolated MMC meeting quality criteria for cell counting. These were expressed as observed-to-expected ratios, after matching for gestational age and spinal level with 41 controls.
Chiari II malformation increased from 30.7% to 91.6% after 16 weeks. The exposed spinal cord displayed early, severe, and progressive neuronal loss: the observed-to-expected count dropped from 17% to ≤2% after 16 weeks. Neuronal loss extended beyond the lesion to the upper levels: in cases <16 weeks, the observed-to-expected motor neuron count was 60% in the adjacent spinal cord, decreasing at a rate of 16% per week. Progressive loss was also found in the upper thoracic cord, but in much smaller proportions. The observed-over-expected ratio of motor neurons was not correlated with the level of myelomeningocele.
Significant neuronal loss is present ≤16 weeks in the exposed cord and progressively extends cranially. Earlier prenatal repair (<16 weeks) could prevent Chiari II malformation in 69.3% of cases, rescue the 17% remaining motor neurons in the exposed cord, and prevent the extension to the upper spinal cord.
Ultrasound examination performed on a 36-year-old woman at 33 weeks of gestation showed the presence of isolated and bilateral ventriculomegaly in the fetus. Array-based comparative genomic ...hybridization (array-CGH) performed on uncultured amniocytes at 35 weeks of gestation revealed a 17q21.31 microdeletion. After genetic counseling, the pregnancy was terminated at 37 weeks of gestation. At autopsy, the fetus displayed facial dysmorphic features and triventricular ventriculomegaly. To our knowledge, this is the first case of a 17q21.31 microdeletion detected prenatally. Our report suggests that array-CGH should be performed when severe ventriculomegaly is observed in prenatal ultrasound examination.
We describe two fetal cases of microphthalmia/anophthalmia, pulmonary agenesis, and diaphragmatic defect. This rare association is known as Matthew-Wood syndrome (MWS; MIM 601186) or by the acronym ..."PMD" (Pulmonary agenesis, Microphthalmia, Diaphragmatic defect). Fewer than ten pre- and perinatal diagnoses of Matthew-Wood syndrome have been described to date. The cause is unknown, and the mode of transmission remains unclear. Most cases have been reported as isolated and sporadic, although recurrence among sibs has been observed once. Our two cases both occurred in consanguineous families, further supporting autosomal recessive transmission. In addition, in one family at least one of the elder sibs presented an evocatively similar phenotype. The spatiotemporal expression pattern of the FGF10 and FGFR2 genes in human embryos and the reported phenotypes of knockout mice for these genes spurred us to examine their coding sequences in our two cases of MWS. While in our patients, no causative sequence variations were identified in FGF10 or FGFR2, this cognate ligand-receptor pair and its downstream effectors remain functional candidates for MWS and similar associations of congenital ocular, diaphragmatic and pulmonary malformations.
Birth defects of the brain result from malformation and dis- ruptions. They remain an important cause of childhood morbidity and mortality. Effective treatments are scarce and prevention strategies ...limited. As aetiological screening is costly and uncertain, genetic counselling remains empirical in most cases.
A pathological study of the malformed brain is the best approach to establish the diagnosis of a brain malformation. It relies on a thorough description of the brain, including its size, external pattern and/or internal configuration. When evaluating a malformed brain two major factors should be considered: (1) malformations result from an arrest of the development at a given time, interfering with subsequent stages of development, leading to a sequence of malforma- tions where the 'primary event' should be distinguished from 'secondary changes'; (2) there is no obvious causal relation- ship when the final morphology of the central nervous system is considered. For example, mutations in different genes involved in a signalling pathway may result in a similar pattern of malformations. In addition, signalling pathways may be a possible target of toxic agents, mimicking malformations caused by genetic factors.
A precise diagnosis will allow rational aetiological screening, with direct benefit for the family, which may serve other families. In addition, it helps to establish a quality assurance process for medical practice, collect solid epidemiological data and conduct research studies. Because of discrepancies observed between human diseases and animal models, research on human material is mandatory. This requires collection of organs, tissues and cells within a legal and ethical framework.
Non-syndromic arthrogryposis multiplex congenita (AMC) is characterized by multiple congenital contractures resulting from reduced fetal mobility. Genetic mapping and whole exome sequencing (WES) ...were performed in 31 multiplex and/or consanguineous undiagnosed AMC families. Although this approach identified known AMC genes, we here report pathogenic mutations in two new genes. Homozygous frameshift mutations in CNTNAP1 were found in four unrelated families. Patients showed a marked reduction in motor nerve conduction velocity (<10 m/s) and transmission electron microscopy (TEM) of sciatic nerve in the index cases revealed severe abnormalities of both nodes of Ranvier width and myelinated axons. CNTNAP1 encodes CASPR, an essential component of node of Ranvier domains which underlies saltatory conduction of action potentials along the myelinated axons, an important process for neuronal function. A homozygous missense mutation in adenylate cyclase 6 gene (ADCY6) was found in another family characterized by a lack of myelin in the peripheral nervous system (PNS) as determined by TEM. Morpholino knockdown of the zebrafish orthologs led to severe and specific defects in peripheral myelin in spite of the presence of Schwann cells. ADCY6 encodes a protein that belongs to the adenylate cyclase family responsible for the synthesis of cAMP. Elevation of cAMP can mimic axonal contact in vitro and upregulates myelinating signals. Our data indicate an essential and so far unknown role of ADCY6 in PNS myelination likely through the cAMP pathway. Mutations of genes encoding proteins of Ranvier domains or involved in myelination of Schwann cells are responsible for novel and severe human axoglial diseases.
Megacystis‐microcolon‐intestinal‐hypoperistalsis syndrome (MMIHS) is a severe congenital visceral myopathy characterized by an abdominal distension due to a large non‐obstructed urinary bladder, a ...microcolon and intestinal hypo‐ or aperistalsis. Most of the patients described to date carry a sporadic heterozygous variant in ACTG2. More recently, recessive forms have been reported and mutations in MYH11, LMOD1, MYLK and MYL9 have been described at the molecular level. In the present report, we describe five patients carrying a recurrent heterozygous variant in ACTG2. Exome sequencing performed in four families allowed us to identify the genetic cause in three. In two families, we identified variants in MMIHS causal genes, respectively a nonsense homozygous variant in MYH11 and a previously described homozygous deletion in MYL9. Finally, we identified compound heterozygous variants in a novel candidate gene, PDCL3, c.143_144del;380G>A, p.(Tyr48Ter);(Cys127Tyr). After cDNA analysis, a complete absence of PDLC3 expression was observed in affected individuals, indicating that both mutated transcripts were unstable and prone to mediated mRNA decay. PDCL3 encodes a protein involved in the folding of actin, a key step in thin filament formation. Presumably, loss‐of‐function of this protein affects the contractility of smooth muscle tissues, making PDCL3 an excellent candidate gene for autosomal recessive forms of MMIHS.
Corpus callosum malformation (CCM) is the most frequent brain malformation observed at birth. Because CCM is a highly heterogeneous condition, the prognosis of fetuses diagnosed prenatally remains ...uncertain, making prenatal counseling difficult.
We evaluated retrospectively a total of 138 fetuses, 117 with CCM observed on prenatal imaging examination, and 21 after postmortem autopsy. On ultrasound and/or magnetic resonance imaging, CCM was either isolated (N = 40) or associated with other neurological (N = 57) or extra cerebral findings (N = 21/20, respectively).
Most fetuses (N = 132) remained without a diagnosis at the time of pregnancy termination. This emphasizes the need to establish a neuropathological classification and to perform a genomic screening using comparative genomic hybridization. A neuropathological examination performed on 138 cases revealed a spectrum of CCMs, classified as follows: agenesis of corpus callosum (55), CC hypoplasia (30), CC dysmorphism (24), and CCM associated with a malformation of cortical development (29). Of interest, after fetopathological examination, only 16/40 malformations were classified as isolated, highlighting the importance of the autopsy following termination of pregnancy. Among the 138 cases, the underlying etiology was found in 46 cases: diabetes (one case), cytomegalovirus infection (one case), 23 chromosome abnormalities, and 21 mendelian conditions.
In our series of 138 cases of CCM, prenatal and postmortem examinations identified a variety of genetic causes. However, no diagnosis could be established in 67% of cases. The classification based on the underlying neurodevelopmental defects paves the way for further genetic studies and genotype-phenotype correlations.
Introduction: Beckwith-Wiedemann syndrome (BWS) is the most common overgrowth syndrome. Clinical features are highly variable, including occasional posterior fossa malformations but no femoral ...shortening. Case report: We report two fetuses with BWS associated with short femurs and corpus callosum hypoplasia. Case 2 was growth restricted. BWS was confirmed by molecular studies showing a loss of methylation at ICR2 at 11p15 chromosomic region in case 1 and a gain of methylation at ICR1 and a loss of methylation at ICR2 locus in case 2. Conclusion: Although the phenotype and the genotype of BWS is now well-known, the presence of corpus callosum abnormalities and short femurs expand the phenotypic spectrum of the disorder.
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