[Neu-Laxova syndrome: Three case reports and a review of the literature]. / Syndrome de Neu-Laxova : rapport de trois cas et revue de la littérature.

INTRODUCTION: The Neu-Laxova syndrome (NLS) is a rare autosomal recessive and early lethal disorder. It is characterized by severe intra-uterine growth retardation, abnormal facial features, ichthyotic skin lesions and severe central nervous system malformations, especially microlissencephaly. Others characteristic features associated with fetal hypokinesia sequence, including arthrogryposis, subcutaneous edema and pulmonary hypoplasia, are frequently reported in NLS. PATIENTS AND METHODS: The clinicopathological characteristics of NLS are described in three cases with striking prenatal diagnostic findings and detailed post-mortem examinations. A review of the literature is undertaken with a focus on molecular basis. RESULTS: We present three new patients with NLS: one stillbirth male and two female newborns, delivered at 29, 35 and 40 weeks of gestational age, respectively. Characteristic ultrasound findings included hydramnios, severe intra-uterine growth restriction, craniofacial and cental nervous system anomalies. The cytogenetic study, performed in one case, was normal. The post-mortem examination revealed characteristic abnormalities in all three cases, that allowed to make a prompt diagnosis of the NLS. Data from these patients suggest that the NLS represents a heterogeneous phenotype. This feature has been highlighted in the literature. CONCLUSION: The SNL is a lethal developmental disorder characterized by phenotypic heterogeneity with striking neurological defects. It is underpinned by genetic heterogeneity. It can be caused by mutations in all three genes involved in de novo L-serine biosynthesis: PHGDH, PSAT1 and PSPH. Hence, the NLS constitutes the most severe end of already known human disease, i.e. serine-deficiency disorder.

A spontaneous Fatp4/Scl27a4 splice site mutation in a new murine model for congenital ichthyosis.

Congenital ichthyoses are life-threatening conditions in humans. We describe here the identification and molecular characterization of a novel recessive mutation in mice that results in newborn lethality with severe congenital lamellar ichthyosis. Mutant newborns have a taut, shiny, non-expandable epidermis that resembles cornified manifestations of autosomal-recessive congenital ichthyosis in humans. The skin is stretched so tightly that the newborn mice are immobilized. The genetic defect was mapped to a region near the proximal end of chromosome 2 by SNP analysis, suggesting Fatp4/Slc27a4 as a candidate gene. FATP4 mutations in humans cause ichthyosis prematurity syndrome (IPS), and mutations of Fatp4 in mice have previously been found to cause a phenotype that resembles human congenital ichthyoses. Characterization of the Fatp4 cDNA revealed a fusion of exon 8 to exon 10, with deletion of exon 9. Genomic sequencing identified an A to T mutation in the splice donor sequence at the 3'-end of exon 9. Loss of exon 9 results in a frame shift mutation upstream from the conserved very long-chain acyl-CoA synthase (VLACS) domain. Histological studies revealed that the mutant mice have defects in keratinocyte differentiation, along with hyperproliferation of the stratum basale of the epidermis, a hyperkeratotic stratum corneum, and reduced numbers of secondary hair follicles. Since Fatp4 protein is present primarily at the stratum granulosum and the stratum spinosum, the hyperproliferation and the alterations in hair follicle induction suggest that very long chain fatty acids, in addition to being required for normal cornification, may influence signals from the stratum corneum to the basal cells that help to orchestrate normal skin differentiation.

Prenatal sonographic assessment and perinatal course of ichthyosis prematurity syndrome.

All cases of ichthyosis prematurity syndrome (IPS), registered at the National Center for Fetal Medicine in Trondheim, Norway between 1987 and 2010 were identified and the findings analyzed. Five fetuses with IPS were identified between 1988 and 2000. All five developed polyhydramnios between 28 and 31 weeks. The fetal stomach appeared to be empty in four cases, and was not described in one case. The fetal skin was described as 'uneven' at ultrasound examination in two cases. Separation of chorionic and amniotic membranes with a peculiar appearance of echo-free fluid in the chorionic cavity and echogenic sediment in the amniotic cavity were observed between 28 + 5 and 32 + 3 weeks in all cases. All fetuses were delivered prematurely between 30 and 34 weeks. All neonates had difficulties in breathing, two developed aspiration pneumonia, and one had bilateral pneumothorax after intubation and died at 6 months because of pulmonary and cardiac sequelae. Prenatal sonographic signs of IPS are separation of the membranes, echogenic amniotic fluid and echo-free chorionic fluid occurring between 28 and 32 weeks' gestation. Delivery occurs at 30-34 weeks and, as there is a high risk of asphyxia, an experienced neonatal intensive care unit team should be present at delivery.

Abca12-mediated lipid transport and Snap29-dependent trafficking of lamellar granules are crucial for epidermal morphogenesis in a zebrafish model of ichthyosis.

Zebrafish (Danio rerio) can serve as a model system to study heritable skin diseases. The skin is rapidly developed during the first 5-6 days of embryonic growth, accompanied by expression of skin-specific genes. Transmission electron microscopy (TEM) of wild-type zebrafish at day 5 reveals a two-cell-layer epidermis separated from the underlying collagenous stroma by a basement membrane with fully developed hemidesmosomes. Scanning electron microscopy (SEM) reveals an ordered surface contour of keratinocytes with discrete microridges. To gain insight into epidermal morphogenesis, we have employed morpholino-mediated knockdown of the abca12 and snap29 genes, which are crucial for secretion of lipids and intracellular trafficking of lamellar granules, respectively. Morpholinos, when placed on exon-intron junctions, were >90% effective in preventing the corresponding gene expression when injected into one- to four-cell-stage embryos. By day 3, TEM of abca12 morphants showed accumulation of lipid-containing electron-dense lamellar granules, whereas snap29 morphants showed the presence of apparently empty vesicles in the epidermis. Evaluation of epidermal morphogenesis by SEM revealed similar perturbations in both cases in the microridge architecture and the development of spicule-like protrusions on the surface of keratinocytes. These morphological findings are akin to epidermal changes in harlequin ichthyosis and CEDNIK syndrome, autosomal recessive keratinization disorders due to mutations in the ABCA12 and SNAP29 genes, respectively. The results indicate that interference of independent pathways involving lipid transport in the epidermis can result in phenotypically similar perturbations in epidermal morphogenesis, and that these fish mutants can serve as a model to study the pathomechanisms of these keratinization disorders.

Second trimester diagnosis of Neu Laxova syndrome.

This is the first report of a prenatally diagnosed case of Neu Laxova syndrome (NLS) from India. This also includes a case of NLS in monochorionic diamniotic twins and two more cases in which we were able to detect most of the features of NLS as early as 19 to 20 weeks by routine antenatal ultrasonography. Severe intrauterine growth retardation (IUGR), microcephaly, central nervous system (CNS) abnormality, joint contractures, and abnormal facies are the major diagnostic features observed in prenatal ultrasonography. Risk factors such as consanguinity and history of intrauterine death or stillbirth in siblings have been noted in all the cases, but none of the three families that were reported had previously had an affected fetus. The spectrum of skin manifestations and frequency of occurrence of major clinical features of the syndrome have been discussed. Review of the literature on NLS and possibility of detecting the syndrome in the second trimester is discussed.

Electron microscopic studies of harlequin fetuses.

Four cases of harlequin fetus of various estimated gestational ages (16, 20, 21, 24 weeks) were examined by light and electron microscopy. When the epidermis was keratinized the following features were commonly found: hyperkeratosis with or without granular cells; dilated hair follicles with plugged keratin; a large number of dense or particle-cored granules in the upper malpighian layer; absence of cementsomes (lamellar bodies); large vacuoles with peripherally located laminations; large mitochondria with vesicular or membranous cristae; and early formation of the marginal band in keratinocytes and abnormal formation of the same in luminal cells of the acrosyringium. A 16-week specimen had no sign of keratinization, which made it difficult to detect these abnormalities; however, it did have large mitochondria in the keratinocytes. The mucous membrane of the lip was thickened but not keratinized.