Microphthalmia and chorioretinal lesions in a girl with an Xp22.2-pter deletion and partial 3p trisomy: clinical observations relevant to Aicardi syndrome gene localization

A case of Aicardi syndrome associated with duplication event of Xp22 including SHOX

BACKGROUND

Aicardi syndrome is a neurodevelopmental disorder characterized by a triad of partial or complete agenesis of the corpus callosum, infantile spasms, and pathognomonic chorioretinal lacunae.

METHODS

Examination, multimodal imaging, and genetic testing were used to guide diagnosis.

RESULTS

We report a case of a pediatric patient who was initially diagnosed with refractory infantile spasms. The patient was unresponsive to conventional antiepileptic therapy, and genetic testing with whole exome and mitochondrial genome sequencing could not identify the underlying cause, so vigabatrin was initiated. The ophthalmic examination under anesthesia for vigabatrin toxicity screening revealed chorioretinal atrophy in the retinal periphery of both eyes, with two 3-disc diameter chorioretinal lacunae superotemporal and inferonasal to the optic nerve in the left eye. Given the neuroimaging findings of corpus callosum hypoplasia with polymicrogyria and ocular findings, the patient was diagnosed with Aicardi syndrome. Genetic testing revealed a novel duplication event at the Xp22 locus.

CONCLUSIONS

Aicardi syndrome, albeit a rare condition, should always be considered in the differential diagnosis when investigating a female child with refractory seizures in early childhood. Genetic testing may help further our understanding of AIS and the search for a genetic etiology.

Linear Skin Defects with Multiple Congenital Anomalies (LSDMCA): An Unconventional Mitochondrial Disorder

Mitochondrial disorders, although heterogeneous, are traditionally described as conditions characterized by encephalomyopathy, hypotonia, and progressive postnatal organ failure. Here, we provide a systematic review of Linear Skin Defects with Multiple Congenital Anomalies (LSDMCA), a rare, unconventional mitochondrial disorder which presents as a developmental disease; its main clinical features include microphthalmia with different degrees of severity, linear skin lesions, and central nervous system malformations. The molecular basis of this disorder has been elusive for several years. Mutations were eventually identified in three X-linked genes, i.e., HCCS, COX7B, and NDUFB11, which are all endowed with defined roles in the mitochondrial respiratory chain. A peculiar feature of this condition is its inheritance pattern: X-linked dominant male-lethal. Only female or XX male individuals can be observed, implying that nullisomy for these genes is incompatible with normal embryonic development in mammals. All three genes undergo X-inactivation that, according to our hypothesis, may contribute to the extreme variable expressivity observed in this condition. We propose that mitochondrial dysfunction should be considered as an underlying cause in developmental disorders. Moreover, LSDMCA should be taken into consideration by clinicians when dealing with patients with microphthalmia with or without associated skin phenotypes.

Aicardi syndrome, an unsolved mystery: Review of diagnostic features, previous attempts, and future opportunities for genetic examination

Aicardi syndrome is a rare, severe neurodevelopmental disorder classically characterized by the triad of infantile spasms, central chorioretinal lacunae, and agenesis of the corpus callosum. Aicardi syndrome only affects females, with the exception of a few males with a 47, XXY chromosome constitution. All cases are de novo and the only cases of definitive recurrence in families are in identical twins. It is now recognized that individuals with Aicardi syndrome commonly exhibit a variety of other neuronal migration defects, eye anomalies, and other somatic features, including skin, skeletal, and craniofacial systems. The etiology of Aicardi syndrome remains unknown despite an international effort exploring different genetic mechanisms. Although various technologies examining candidate genes, copy number variation, skewing of X-chromosome inactivation, and whole-exome sequences have been explored, no strong genetic candidates have been identified to date. New technologies that can detect low-level mosaicism and balanced rearrangements, as well as platforms examining changes at the DNA and chromatin level affecting regulatory regions are all potential avenues for future studies that may one day solve the mystery of the etiology of Aicardi syndrome.

Aicardi syndrome associated with autosomal genomic imbalance: coincidence or evidence for autosomal inheritance with sex-limited expression?

Aicardi syndrome (AIS), a rare neurodevelopmental disorder thought to be caused by an X-linked dominant mutation, is characterized by 3 main features: agenesis of corpus callosum, infantile spams and chorioretinal lacunae. A genome-wide study of a girl with AIS lead us to identify a 6q deletion;12q duplication, derived from a maternal 6q;12q translocation. The two intellectually impaired brothers of the proband showed the same genomic anomalies, but not the constellation of features characterizing the AIS. This could be either a coincidental observation of 2 rare conditions, but can also suggest an alternative hypothesis for the genetic etiology of AIS, indicating the existence of a subset of autosomal genes whose mutation could act in a sex-confined manner.

Molecular karyotyping by array CGH in a Russian cohort of children with intellectual disability, autism, epilepsy and congenital anomalies

Background

Array comparative genomic hybridization (CGH) has been repeatedly shown to be a successful tool for the identification of genomic variations in a clinical population. During the last decade, the implementation of array CGH has resulted in the identification of new causative submicroscopic chromosome imbalances and copy number variations (CNVs) in neuropsychiatric (neurobehavioral) diseases. Currently, array-CGH-based technologies have become an integral part of molecular diagnosis and research in individuals with neuropsychiatric disorders and children with intellectual disability (mental retardation) and congenital anomalies. Here, we introduce the Russian cohort of children with intellectual disability, autism, epilepsy and congenital anomalies analyzed by BAC array CGH and a novel bioinformatic strategy.

Results

Among 54 individuals highly selected according to clinical criteria and molecular and cytogenetic data (from 2426 patients evaluated cytogenetically and molecularly between November 2007 and May 2012), chromosomal imbalances were detected in 26 individuals (48%). In two patients (4%), a previously undescribed condition was observed. The latter has been designated as meiotic (constitutional) genomic instability resulted in multiple submicroscopic rearrangements (including CNVs). Using bioinformatic strategy, we were able to identify clinically relevant CNVs in 15 individuals (28%). Selected cases were confirmed by molecular cytogenetic and molecular genetic methods. Eight out of 26 chromosomal imbalances (31%) have not been previously reported. Among them, three cases were co-occurrence of subtle chromosome 9 and 21 deletions.

Conclusions

We conducted an array CGH study of Russian patients suffering from intellectual disability, autism, epilepsy and congenital anomalies. In total, phenotypic manifestations of clinically relevant genomic variations were found to result from genomic rearrangements affecting 1247 disease-causing and pathway-involved genes. Obviously, a significantly lesser part of them are true candidates for intellectual disability, autism or epilepsy. The success of our preliminary array CGH and bioinformatic study allows us to expand the cohort. According to the available literature, this is the first comprehensive array CGH evaluation of a Russian cohort of children with neuropsychiatric disorders and congenital anomalies.

Goltz-Gorlin (focal dermal hypoplasia) and the microphthalmia with linear skin defects (MLS) syndrome: no evidence of genetic overlap

Focal dermal hypoplasia (FDH) is an X-linked developmental disorder with male lethality characterized by patchy dermal hypoplasia, skeletal and dental malformations, and microphthalmia or anophthalmia. Recently, heterozygous loss-of-function mutations in the PORCN gene have been described to cause FDH. FDH shows some clinical overlap with the microphthalmia with linear skin defects (MLS) syndrome, another X-linked male lethal condition, associated with mutations of HCCS in the majority of cases. We performed DNA sequencing of PORCN in 13 female patients with the clinical diagnosis of FDH as well as four female patients with MLS syndrome and no mutation in HCCS. We identified PORCN mutations in all female patients with FDH. Eleven patients seem to have constitutional PORCN alterations in the heterozygous state and two individuals are mosaic for the heterozygous sequence change in PORCN. No PORCN mutation was identified in the MLS-affected patients, providing further evidence that FDH and MLS do not overlap genetically. X chromosome inactivation (XCI) analysis revealed a random or slightly skewed XCI pattern in leukocytes of individuals with intragenic PORCN mutation suggesting that defective PORCN does not lead to selective growth disadvantage, at least in leukocytes. We conclude that the PORCN mutation detection rate is high in individuals with a clear-cut FDH phenotype and somatic mosaicism can be present in a significant proportion of patients with mild or classic FDH.

Molecular pathogenesis of childhood brain tumors

In the last decade, the molecular biology revolution has advanced considerably. These advances have enhanced our understanding of the genetic underpinnings of human brain tumors in general, and pediatric brain tumors in particular. We now know that many pediatric brain tumors arise from disturbances in developmentally regulated signaling pathways. The medulloblastoma, a tumor in which the developmental Hedgehog and WNT pathways have gone awry, is a prime example of this. New techniques in genetic engineering have allowed for the creation of sophisticated mouse models of brain tumors that recapitulate the human disease. Many laboratories are now using cDNA microarrays to study the expression level of thousands of genes that may be aberrantly expressed in brain tumors when compared to normal control cells. In the next decade, the use of several new molecular techniques to establish brain tumor diagnoses will likely become standard tools in the diagnostics and treatment stratification of children with central nervous system tumors.

Persistance et hyperplasie du vitré primitif et syndrome d’Aicardi

INTRODUCTION

Aicardi syndrome is characterized by infantile spasms, agenesis of the corpus callosum and chorioretinal lacunae. This disorder affects mostly females, with early embryonic lethality in males. Numerous general and ocular disorders may be associated with this affection. We present here a case of persistent hyperplastic primary vitreous (PHPV) in association with Aicardi syndrome in a 30-year-old woman.

CASE REPORT

The authors report a case of a 30-year-old woman with Aicardi syndrome associated with persistent hyperplastic primary vitreous.

DISCUSSION

Aicardi syndrome is a polymalformative disease occurring at an early period of embryogenesis. It can affect many ocular structures. This syndrome is essentially described in female children, who rarely reach an adult age. The observation we report is particular because of the patient's age (30-years-old) and the association with a persistent hyperplastic primary vitreous, exceptional in this context.

CONCLUSION

With a review of the literature, the Authors discuss the clinical neuroradiological and prognostic aspects of this polymalformative syndrome and different associated general and ocular abnormalities, emphasizing particularly those of persistent hyperplastic primary vitreous in this affection.

[Aicardi syndrome with favorable outcome]

BACKGROUND

Aicardi syndrome is usually associated with a very poor outcome.

CASE REPORT

We report a particular case of Aicardi syndrome characterised by a partial agenesis of the corpus callosum associated with an arachnoidal interhemispheric cystic formation, and by a complete control of epilepsy and a favorable outcome regarding visual and psychomotor performances.

CONCLUSION

A better prognosis could be expected in Aicardi syndrome when spasms occur lately and are not preceded by partial seizures, when agenesis of corpus callosum is partial and especially when chorioretinal lacunae are small, isolated, few and spare the macula.

Characterization of a novel chromo domain gene in xp22.3 with homology to Drosophila msl-3

The Drosophila male-specific lethal (MSL) genes regulate transcription from the male X chromosome in a dosage compensation pathway that equalizes X-linked gene expression in males and females. The members of this gene family, including msl-1, msl-2, msl-3, mle, and mof, encode proteins with no sequence homology. However, mutations in each of these genes produce a similar phenotype: sex-specific lethality of male embryos caused by the failure of mutants to increase transcription from the single male X chromosome. The MSL gene products assemble into a multiprotein transcriptional activation complex at hundreds of sites along the chromatin of the X chromosome. Here we report the isolation and characterization of a human gene, named MSL3L1, that encodes a protein with significant homology to Drosophila MSL-3 in three distinct regions, including two putative chromo domains. MSL3L1 was identified by database queries with genomic sequence from BAC GS-590J6 (GenBank AC0004554) in Xp22.3 and was evaluated as a candidate gene for several developmental disorders mapping to this region, including OFD1 and SED tarda, as well as Aicardi syndrome and Goltz syndrome.

Reticulolinear aplasia cutis congenita of the face and neck: a distinctive cutaneous manifestation in several syndromes linked to Xp22

A distinct form of aplasia cutis congenita presenting as linear facial skin defects has been described under a variety of names as Xp deletion syndrome. MIDAS (microphthalmia, dermal aplasia and sclerocornea) syndrome, MLS (microphthalmia and linear skin defects) and Gazali-Temple syndrome. The syndrome is lethal in males, and its severity in females varies from a relatively mild residual facial scarring with short stature to lethal developmental organ malformations. A new case with peculiar ultrastructural findings is presented. A review of the literature suggests that these associations represent a series of contiguous-gene syndromes.

Second 46,XX male with MLS syndrome

We report on a second 46,XX male with microphthalmia with linear skin defects (MLS) syndrome. In addition to microphthalmia and linear skin streaks, he had a secundum ASD, hypospadias with chordee, anal fistula, and agenesis of corpus callosum with colpocephaly. Biopsy of a linear streak showed smooth muscle hamartomata rather than the presumed dermal aplasia. Detailed ophthalmologic examination did not show retinal lacunae typical of Aicardi syndrome. DNA studies with distal Xp specific probes indicated a deletion in one X chromosome and fluorescence in situ hybridization (FISH) studies with X- and Y-specific probes demonstrated the presence of a derivative X chromosome from an X;Y translocation.

Monozygotic twins discordant for Aicardi syndrome

Aicardi syndrome is a developmental disorder characterised by agenesis of the corpus callosum, retinal lacunae, seizures, and developmental delay. It is believed to be X linked with lethality in males. We report a set of monozygotic female twins one of whom is healthy and intellectually normal while the other has the classical Aicardi phenotype with profound retardation. Family history is negative. Both had normal karyotypes. Monozygosity was established by blood grouping, chromosomal heteromorphisms, and DNA analysis using six hypervariable probes (five autosomal and one X linked) and three X linked RFLP probes. We tested the hypothesis that preferential inactivation of a different X chromosome had occurred in each girl. Methylation sensitive RFLP analysis of DNA from EBV transformed B lymphocytes and cultured skin fibroblasts using MspI/HpaII digestion and probing with M27 beta showed a very similar pattern of X inactivation in both twins with no evidence of preferential expression of one particular X chromosome. We conclude that the abnormalities in the affected twin are probably the consequence of a postzygotic mutation in early embryonic development.

Xp microdeletion syndrome characterized by pathognomonic linear skin defects on the head and neck

We describe a new case of a rare syndrome characterized by ocular abnormalities and pathognomonic linear skin defects. This syndrome is the result of an unbalanced translocation resulting in a deletion of the distal end of the short arm of the X chromosome. We report the thirteenth case and review the clinical and cytogenetic aspects of this disorder. In addition we discuss new findings pertaining to the histopathology of the skin lesions.

Mild phenotypic effects of a de novo deletion Xpter-->Xp22.3 and duplication 3pter-->3p23

We report on a girl with a de novo monosomy Xpter-->Xp22.3 and trisomy 3pter-->3p23, normal development and stature, mildly affected phenotype, and learning disabilities with a low normal level of intelligence. Late replication studies using BudR demonstrated that the entire der(X) was inactive in 30% of cells. In 62% of cells the inactivation did not spread to the autosomal segment in the der(X). The normal X was inactivated in 8% of cells. Quantitative X-inactivation studies using the human androgen receptor locus assay (HAR) on peripheral leukocytes and buccal epithelial cells showed extreme skewing of methylation (90.4% of the paternal allele). The correlation of cytogenetic and molecular data suggest that the mild phenotype of the proposita is most likely due to preferential inactivation of the entire der(X), which seems to be of paternal origin.

Microphthalmia with linear skin defects (MLS) syndrome: clinical, cytogenetic, and molecular characterization

The microphthalmia with linear skin defects (MLS) syndrome (MIM 309801) is a severe developmental disorder observed in XX individuals with distal Xp segmental monosomy. The phenotype of this syndrome overlaps with that of both Aicardi (MIM 304050) and Goltz (MIM 305600) syndromes, two X-linked dominant, male-lethal disorders. Here we report the clinical, cytogenetic, and molecular characterization of 3 patients with this syndrome. Two of these patients are females with a terminal Xpter-p22.2 deletion. One of these 2 patients had an aborted fetus with anencephaly and the same chromosome abnormality. The third patient is an XX male with Xp/Yp exchange spanning the SRY gene which results in distal Xp monosomy. The extensive clinical variability observed in these patients and the results of the molecular analysis suggest that X-inactivation plays an important role in determining the phenotype of the MLS syndrome. We propose that the MLS, Aicardi, and Goltz syndromes are due to the involvement of the same gene(s), and that different patterns of X-inactivation are responsible for the phenotypic differences observed in these 3 disorders. However, we cannot rule out that each component of the MLS phenotype is caused by deletion of a different gene (a contiguous gene syndrome).

MIDAS syndrome (microphthalmia, dermal aplasia, and sclerocornea): an X-linked phenotype distinct from Goltz syndrome

Bilateral microphthalmia with blepharophimosis, linear lesions of dermal aplasia involving the face, and microcephaly were present in a newborn girl who died at age 9 months from cardiomyopathy resulting in ventricular fibrillation. Autopsy showed an atrial septum defect, persistent gross trabeculation of the left ventricle, and an arteria lusoria. This case represents a further example of a new entity for which we propose the term MIDAS syndrome. The acronym stands for microphthalmia, dermal aplasia, and sclerocornea. Our patient is the second with this syndrome to have a major congenital heart defect. Cytogenetic studies reported in previous cases indicate that the underlying gene defect can be assigned to Xp22.3. This new X-linked male-lethal trait should be distinguished from focal dermal hypoplasia that will be found to map elsewhere on the X-chromosome.

A high resolution deletion map of human chromosome Xp22

We have developed a 32-interval deletion panel for human chromosome Xp22 spanning about 30 megabases of genomic DNA. DNA samples from 50 patients with chromosomal rearrangements involving Xp22 were tested with 60 markers using a polymerase chain reaction strategy. The ensuing deletion map allowed us to confirm and refine the order of previously isolated and newly developed markers. Our mapping panel will provide the framework for mapping new sequences, for orienting chromosome walks in the region and for projects aimed at isolating genes responsible for diseases mapping to Xp22.

Xp22.3 microdeletion syndrome with microphthalmia, sclerocornea, linear skin defects, and congenital heart defects

We report on an infant girl with congenital erythematous, linear skin lesions on face and neck, bilateral microphthalmia, sclerocornea, cataracts, and a complex cardiac anomaly including atrial septal and ventricular septal defects. This patient had an Xp22.3 microdeletion and a chromosome satellite on the abnormal X p-arm. The abnormal X chromosome was late replicating in peripheral blood lymphocytes and cultured skin fibroblasts. Four other patients with similar congenital anomalies and Xp deficiency have been reported previously and are compared with this patient. One patient had an interstitial or terminal deletion, but in others the material translocated to Xp22.3 was variable (Yq material in two patients, and Yp material and an unidentifiable satellite in one patient each). Several mechanisms are suggested by which this chromosome abnormality might produce this phenotype in these patients. Our patient is the first with this syndrome to have a congenital heart defect.

Ophthalmological, skeletal, and cardiac abnormalities in sibs born to consanguineous parents: a new syndrome?

We report on a sibship from a consanguineous couple consisting of one boy with anophthalmia, one boy with buphthalmos and multiple congenital skeletal, muscle, and cardiac abnormalities, and a stillborn girl with anophthalmia and cardiac and skeletal abnormalities. A possible new syndrome of autosomal recessive inheritance and variable expressivity is discussed, comparing this report with others.

Hereditary microphthalmia with colobomatous cyst

We examined five members of a highly inbred kinship who had isolated microphthalmia associated with colobomatous cysts and various other ocular lesions. They were all offspring of consanguineous (first cousins) and unaffected parents. Microphthalmia in this kindred was transmitted as an autosomal recessive trait. Ultrasonography was effective for prenatal diagnosis in two pregnancies at risk.