Leukodystrophy in patients with ovarian dysgenesis

Amino-acyl tRNA synthetases associated with leukodystrophy

Amino-acyl tRNA synthetases (ARSs) are enzymes that catalyze the amino-acylation reaction of a specific amino acid and its cognate tRNA and are divided into type 1 (cytosolic) and type 2 (mitochondrial). In this chapter leukodystrophies caused by tRNA synthetase deficiencies are reviewed.

Association Between Late-Onset Leukoencephalopathy With Vanishing White Matter and Compound Heterozygous EIF2B5 Gene Mutations: A Case Report and Review of the Literature

Leukoencephalopathy with vanishing white matter (LVWM) is an autosomal recessive disease. Ovarioleukodystrophy is defined as LVWM in females showing signs or symptoms of gradual ovarian failure. We present a 38-year-old female with ovarioleukodystrophy who showed status epilepticus, gait instability, slurred speech, abdominal tendon hyperreflexia, and ovarian failure. Abnormal EEG, characteristic magnetic resonance, and unreported EIF2B5 compound heterozygous mutations [c.1016G>A (p.R339Q) and c.1157G>A (p.G386D)] were found. Furthermore, the present report summarizes 20 female patients with adult-onset ovarioleukodystrophy and EIF2B5 gene mutations. In conclusion, a new genetic locus for LVWM was discovered. Compared with previous cases, mutations at different EIF2B5 sites might have different clinical manifestations and obvious clinical heterogeneity.

A novel hypomorphic splice variant in EIF2B5 gene is associated with mild ovarioleukodystrophy

OBJECTIVE

To identify the genetic cause in an adult ovarioleukodystrophy patient resistant to diagnosis.

METHODS

We applied whole-exome sequencing (WES) to a vanishing white matter disease patient associated with premature ovarian failure at 26 years of age. We functionally tested an intronic variant by RT-PCR on patient's peripheral blood mononuclear cells (PBMC) and by minigene splicing assay.

RESULTS

WES analysis identified two novel variants in the EIF2B5 gene: c.725A > G (p.Tyr242Cys) and an intronic noncanonical mutation (c.1156 + 13G>A). This intronic mutation resulted into generation of various isoforms both in patient's PBMC and in the minigene splicing assay, showing that ~20% residual wild-type isoform is still expressed by the intronic-mutated allele alone, concordant with an hypomorphic effect of this variant.

CONCLUSION

We report two novel variants in EIF2B5, one of them a noncanonical intronic splice variant, located at a +13 intronic position. This position is mutated only in 0.05% of ClinVar intronic mutations described so far. Furthermore, we illustrate how minigene splicing assay may be advantageous when validating splice-altering variants, in this case highlighting the coexistence of wild-type and mutated forms, probably explaining this patient's milder, late-onset phenotype.

An AARS variant as the likely cause of Swedish type hereditary diffuse leukoencephalopathy with spheroids

Swedish type Hereditary Diffuse Leukoencephalopathy with Spheroids (HDLS-S) is a severe adult-onset leukoencephalopathy with the histopathological hallmark of neuraxonal degeneration with spheroids, described in a large family with a dominant inheritance pattern. The initial stage of the disease is dominated by frontal lobe symptoms that develop into a rapidly advancing encephalopathy with pyramidal, deep sensory, extrapyramidal and optic tract symptoms. Median survival is less than 10 years. Recently, pathogenic mutations in CSF1R were reported in a clinically and histologically similar leukoencephalopathy segregating in several families. Still, the cause of HDLS-S remained elusive since its initial description in 1984, with no CSF1R mutations identified in the family. Here we update the original findings associated with HDLS-S after a systematic and recent assessment of several family members. We also report the results from exome sequencing analyses indicating the p.Cys152Phe variant in the alanyl tRNA synthetase (AARS) gene as the probable cause of this disease. The variant affects an amino acid located in the aminoacylation domain of the protein and does not cause differences in splicing or expression in the brain. Brain pathology in one case after 10 years of disease duration showed the end stage of the disease to be characterized by widespread liquefaction of the white matter leaving only some macrophages and glial cells behind the centrifugally progressing front. These results point to AARS as a candidate gene for rapidly progressing adult-onset CSF1R-negative leukoencephalopathies.

AARS2 Compound Heterozygous Variants in a Case of Adult-Onset Leukoencephalopathy With Axonal Spheroids and Pigmented Glia

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), usually referred to as hereditary diffuse leukoencephalopathy with spheroids or pigmentary orthochromatic leukodystrophy, is genetically caused by CSF1R mutations. AARS2 was recently confirmed to be another causative gene in a series of CSF1R-negative ALSP cases. We report a case of adult-onset leukoencephalopathy with ALSP with AARS2 variants. A 34-year-old woman presented with 2 years of motor and cognitive deterioration with severely impaired cortical functions and rigid spasticity. Brain magnetic resonance imaging showed a confluent, patchy, and predominantly frontoparietal, periventricular pattern of white matter lesions, with relatively preserved subcortical U-fibers. Brain biopsy revealed axonal spheroids, severe demyelination and pigmented macrophages. Genetic analyses revealed compound heterozygous c.1691T>C and c.179C>A variants in the AARS2 gene. CSF1R mutation testing was negative. Our findings proved adult-onset leukoencephalopathy with spheroids and pigmented glia to be a genetically heterogeneous disease entity. The selective brain involvement without ovarian failure might be a new subtype in AARS2 mutations related to ALSP.

Adult-onset vanishing white matter disease with the EIF2B2 gene mutation presenting as menometrorrhagia

Background

Vanishing white matter disease (VWMD) is one of the most prevalent inherited leukoencephalopathies, which generally presents in childhood as a progressive disorder while less beginning in adulthood. The present report describes the clinical, neuroimaging, and genetic findings of a female patient with adult-onset VWMD. In addition, to provide a clearer delineation of the clinical and genetic characteristics of female adult-onset VWMD patients, 32 genetically confirmed female adult-onset EIF2B-mutated cases are summarized.

Case presentation

The patient described here suffered from long-term menometrorrhagia prior to manifesting progressive neurological impairments that included tremors, bilateral pyramidal tract injury, cerebellar ataxia, and dementia. To the best of our knowledge, this is the first female patient with adult-onset VWMD suffering from long-term menometrorrhagia attributed to the c.254 T > A and c.496A > G mutations in the EIF2B2 gene; the c.496A > G mutation has not been reported in previous studies. The patient also exhibited metabolic dysfunction. The present findings widen the spectrum of phenotypic heterogeneity observed in VWMD patients.

Conclusions

The present report summarizes 33 female patients with adult-onset VWMD to provide an overview of the clinical and genetic characteristics of this disorder and ovarioleukodystrophy. The mean age of clinical onset in female patients with adult-onset VWMD was 36.8 years and the neurological symptoms primarily included motor and cognitive dysfunction such as paraparesis, cerebellar ataxia, and executive deficits. In addition, ovarian failure occurred in all of these female patients and usually preceded the neurological symptoms. Furthermore, several patients also suffered from metabolic dysfunction. All 33 patients had mutations on EIF2B1–5, and of these, the c.338 G > A mutation in the EIF2B5 gene (p.Arg113His) was the most common. These findings suggest that clinicians should be aware of adult-onset forms of VWMD as well as its typical magnetic resonance imaging (MRI) and clinical characteristics although this pathology is usually recognized as a pediatric disorder. No curative treatment is presently available, and thus early recognition is important to prevent triggering events and to allow for genetic counseling.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1429-9) contains supplementary material, which is available to authorized users.

Vanishing white matter: a leukodystrophy due to astrocytic dysfunction

VWM is one of the most prevalent leukodystrophies with unique clinical, pathological and molecular features. It mostly affects children, but may develop at all ages, from birth to senescence. It is dominated by cerebellar ataxia and susceptible to stresses that act as factors provoking disease onset or episodes of rapid neurological deterioration possibly leading to death. VWM is caused by mutations in any of the genes encoding the five subunits of the eukaryotic translation initiation factor 2B (eIF2B). Although eIF2B is ubiquitously expressed, VWM primarily manifests as a leukodystrophy with increasing white matter rarefaction and cystic degeneration, meager astrogliosis with no glial scarring and dysmorphic immature astrocytes and increased numbers of oligodendrocyte progenitor cells that are restrained from maturing into myelin-forming cells. Recent findings point to a central role for astrocytes in driving the brain pathology, with secondary effects on both oligodendroglia and axons. In this, VWM belongs to the growing group of astrocytopathies, in which loss of essential astrocytic functions and gain of detrimental functions drive degeneration of the white matter. Additional disease mechanisms include activation of the unfolded protein response with constitutive predisposition to cellular stress, failure of astrocyte-microglia crosstalk and possibly secondary effects on the oxidative phosphorylation. VWM involves a translation initiation factor. The group of leukodystrophies due to defects in mRNA translation is also growing, suggesting that this may be a common disease mechanism. The combination of all these features makes VWM an intriguing natural model to understand the biology and pathology of the white matter.

New Insights in Vanishing White Matter Disease: Isolated Bilateral Optic Neuropathy in Adult Onset Disease

BACKGROUND

Vanishing white matter disease (VWMD) is a rare disease affecting cerebral white matter. The adult form is even rarer and manifests with motor symptoms, behavioral problems, and dementia. There is no treatment and progression is inevitable. We describe a case with atypical manifestations and an unusual course.

METHODS

Description of a 42-year-old man with VWMD complaining of progressive visual loss in the right eye.

RESULTS

The patient's visual acuity was 20/60, right eye, and 20/25, left eye, with pale optic nerves bilaterally. MRI showed atrophy of the corpus callosum, diffuse rarefaction of cerebral white matter including the anterior and posterior visual pathways.

CONCLUSION

Our patient had no further symptoms besides loss of visual acuity, which is rare in patients with VWMD of the same age and genetic mutation.

Leukodystrophies: a proposed classification system based on pathological changes and pathogenetic mechanisms

Leukodystrophies are genetically determined disorders characterized by the selective involvement of the central nervous system white matter. Onset may be at any age, from prenatal life to senescence. Many leukodystrophies are degenerative in nature, but some only impair white matter function. The clinical course is mostly progressive, but may also be static or even improving with time. Progressive leukodystrophies are often fatal, and no curative treatment is known. The last decade has witnessed a tremendous increase in the number of defined leukodystrophies also owing to a diagnostic approach combining magnetic resonance imaging pattern recognition and next generation sequencing. Knowledge on white matter physiology and pathology has also dramatically built up. This led to the recognition that only few leukodystrophies are due to mutations in myelin- or oligodendrocyte-specific genes, and many are rather caused by defects in other white matter structural components, including astrocytes, microglia, axons and blood vessels. We here propose a novel classification of leukodystrophies that takes into account the primary involvement of any white matter component. Categories in this classification are the myelin disorders due to a primary defect in oligodendrocytes or myelin (hypomyelinating and demyelinating leukodystrophies, leukodystrophies with myelin vacuolization); astrocytopathies; leuko-axonopathies; microgliopathies; and leuko-vasculopathies. Following this classification, we illustrate the neuropathology and disease mechanisms of some leukodystrophies taken as example for each category. Some leukodystrophies fall into more than one category. Given the complex molecular and cellular interplay underlying white matter pathology, recognition of the cellular pathology behind a disease becomes crucial in addressing possible treatment strategies.

Ovarioleukodystrophy due to EIF2B5 mutations

Ovarioleukodystrophy-the co-occurrence of leukodystrophy and premature ovarian failure-is a rare presentation now recognised to be part of the clinical spectrum of vanishing white matter disease. We describe a woman with epilepsy and neuroimaging changes consistent with leukoencephalopathy who presented with non-convulsive status epilepticus after starting hormone replacement therapy in the context of premature ovarian failure. Genetic testing confirmed her to be a compound heterozygote for EIF2B5 mutations; the gene encodes a subunit of eukaryotic translation initiation factor 2B. Mutations in EIF2B1-5 result in vanishing white matter disease. We highlight the importance of ovarian failure as a diagnostic pointer to eukaryotic translation initiation factor 2B (eIF2B)-related ovarioleukodystrophy and present a brief literature review of ovarioleukodystrophy.

Genetics of primary ovarian insufficiency: new developments and opportunities

BACKGROUND

Primary ovarian insufficiency (POI) is characterized by marked heterogeneity, but with a significant genetic contribution. Identifying exact causative genes has been challenging, with many discoveries not replicated. It is timely to take stock of the field, outlining the progress made, framing the controversies and anticipating future directions in elucidating the genetics of POI.

METHODS

A search for original articles published up to May 2015 was performed using PubMed and Google Scholar, identifying studies on the genetic etiology of POI. Studies were included if chromosomal analysis, candidate gene screening and a genome-wide study were conducted. Articles identified were restricted to English language full-text papers.

RESULTS

Chromosomal abnormalities have long been recognized as a frequent cause of POI, with a currently estimated prevalence of 10-13%. Using the traditional karyotype methodology, monosomy X, mosaicism, X chromosome deletions and rearrangements, X-autosome translocations, and isochromosomes have been detected. Based on candidate gene studies, single gene perturbations unequivocally having a deleterious effect in at least one population include Bone morphogenetic protein 15 (BMP15), Progesterone receptor membrane component 1 (PGRMC1), and Fragile X mental retardation 1 (FMR1) premutation on the X chromosome; Growth differentiation factor 9 (GDF9), Folliculogenesis specific bHLH transcription factor (FIGLA), Newborn ovary homeobox gene (NOBOX), Nuclear receptor subfamily 5, group A, member 1 (NR5A1) and Nanos homolog 3 (NANOS3) seem likely as well, but mostly being found in no more than 1-2% of a single population studied. Whole genome approaches have utilized genome-wide association studies (GWAS) to reveal loci not predicted on the basis of a candidate gene, but it remains difficult to locate causative genes and susceptible loci were not always replicated. Cytogenomic methods (array CGH) have identified other regions of interest but studies have not shown consistent results, the resolution of arrays has varied and replication is uncommon. Whole-exome sequencing in non-syndromic POI kindreds has only recently begun, revealing mutations in the Stromal antigen 3 (STAG3), Synaptonemal complex central element 1 (SYCE1), minichromosome maintenance complex component 8 and 9 (MCM8, MCM9) and ATP-dependent DNA helicase homolog (HFM1) genes. Given the slow progress in candidate-gene analysis and relatively small sample sizes available for GWAS, family-based whole exome and whole genome sequencing appear to be the most promising approaches for detecting potential genes responsible for POI.

CONCLUSION

Taken together, the cytogenetic, cytogenomic (array CGH) and exome sequencing approaches have revealed a genetic causation in ∼20-25% of POI cases. Uncovering the remainder of the causative genes will be facilitated not only by whole genome approaches involving larger cohorts in multiple populations but also incorporating environmental exposures and exploring signaling pathways in intragenic and intergenic regions that point to perturbations in regulatory genes and networks.

Genetics of female infertility due to anomalies of the ovary and mullerian ducts

Genetic factors are pivotal in reproductive development and subsequent reproductive processes. If disturbed, infertility can occur. In the female, genetic factors affecting the ovary and the uterus are not uncommon causes of infertility. Terminal deletions on the X long arm and X short arm and X chromosomal mosaicism have long been accepted as causes of premature ovarian failure (POF). Responsible genes on the X have not yet elucidated. Attractive candidate genes for POF also exist on autosomes, and in over a dozen genes molecular perturbations are documented in non-syndromic POF. The most common single-gene cause of POF is premutation carriers for FMR1 (fragile X syndrome). As other candidate genes and additional ethnic groups are interrogated, the proportion of POF cases due to single-gene mutation will increase. Among uterine anomalies, incomplete mullerian fusion is most common. Increased recurrence risks for first-degree relatives confirm a role for genetic factors; interrogation of candidate genes is under way.

Novel (ovario) leukodystrophy related to AARS2 mutations

OBJECTIVES

The study was focused on leukoencephalopathies of unknown cause in order to define a novel, homogeneous phenotype suggestive of a common genetic defect, based on clinical and MRI findings, and to identify the causal genetic defect shared by patients with this phenotype.

METHODS

Independent next-generation exome-sequencing studies were performed in 2 unrelated patients with a leukoencephalopathy. MRI findings in these patients were compared with available MRIs in a database of unclassified leukoencephalopathies; 11 patients with similar MRI abnormalities were selected. Clinical and MRI findings were investigated.

RESULTS

Next-generation sequencing revealed compound heterozygous mutations in AARS2 encoding mitochondrial alanyl-tRNA synthetase in both patients. Functional studies in yeast confirmed the pathogenicity of the mutations in one patient. Sanger sequencing revealed AARS2 mutations in 4 of the 11 selected patients. The 6 patients with AARS2 mutations had childhood- to adulthood-onset signs of neurologic deterioration consisting of ataxia, spasticity, and cognitive decline with features of frontal lobe dysfunction. MRIs showed a leukoencephalopathy with striking involvement of left-right connections, descending tracts, and cerebellar atrophy. All female patients had ovarian failure. None of the patients had signs of a cardiomyopathy.

CONCLUSIONS

Mutations in AARS2 have been found in a severe form of infantile cardiomyopathy in 2 families. We present 6 patients with a new phenotype caused by AARS2 mutations, characterized by leukoencephalopathy and, in female patients, ovarian failure, indicating that the phenotypic spectrum associated with AARS2 variants is much wider than previously reported.

Hypogonadism and neurological diseases

Affected patients with hypogonadism have unnaturally low amounts of sex hormones that produce male and female sex characteristics. Males who suffer from this condition lack testosterone, while females fail to produce enough estrogen. Hypogonadism may be present at birth, or it may take effect years later following injury or illness to the sex glands. Hypogonadism has remarkable associations with variable medical disorders; however, it is characterized by a distinctive association with variable neurological disorders: such as epilepsy, ataxia, dysmyelination, nerve muscle disease, movement disorders, mental retardation and deafness. The remarkable neurological diseases with hypogonadism should not basically be regarded as coincidental findings, but possibly related to an intrinsic pathophysiological association.

Adult-onset vanishing white matter disease due to a novel EIF2B3 mutation

OBJECTIVE

To report a novel mutation in the gene EIF2B3 responsible for a late-onset form of vanishing white matter disease.

DESIGN

Case report.

SETTING

University teaching hospital.

PATIENT

A 29-year-old pregnant woman with a history of premature ovarian failure and hemiplegic migraines presented with a 10-week history of progressive confusion and headaches. Magnetic resonance imaging of the brain revealed a diffuse leukoencephalopathy.

RESULTS

Sequencing of the exons and intron boundaries of EIF2B3 uncovered 2 missense mutations: c.260C>T(p.Ala87Val) and c.272G>A(p.Arg91His). To our knowledge,the latter missense mutation has never been previously reported.

CONCLUSION

This is the second report of adult-onset vanishing white matter disease due to mutations in EIF2B3 and the first report of the c.272G>A (p.Arg91His) missense mutation.

Ovarioleukodystrophy: report of a case with the c.338G>A (p.Arg113His) mutation on exon 3 and the c.896G>A (p.Arg299His) mutation on exon 7 of the EIF2B5 gene

The authors present a 28-year-old lady with progressive neurological deterioration beginning in childhood. She had clinical, radiological and genetic features of ovarioleukodystrophy. This is part of the spectrum of vanishing white matter disease and the first such case reported in the UK. The authors also discuss the literature on the disease.

Leukoencephalopathy with vanishing white matter: a review

Vanishing white matter (VWM) is one of the most prevalent inherited childhood leukoencephalopathies, but this may affect people of all ages, including neonates and adults. It is a progressive disorder clinically dominated by cerebellar ataxia and in which minor stress conditions, such as fever or mild trauma, provoke major episodes of neurologic deterioration. Typical pathological findings include increasing white matter rarefaction and cystic degeneration, oligodendrocytosis with highly characteristic foamy oligodendrocytes, meager astrogliosis with dysmorphic astrocytes, and loss of oligodendrocytes by apoptosis. Vanishing white matter is caused by mutations in any of the genes encoding the 5 subunits of the eukaryotic translation initiation factor 2B (eIF2B), EIF2B1 through EIF2B5. eIF2B is a ubiquitously expressed protein complex that plays a crucial role in regulating the rate of protein synthesis. Vanishing white matter mutations reduce the activity of eIF2B and impair its function to couple protein synthesis to the cellular demands in basal conditions and during stress. Reduced eIF2B activity leads to sustained improper activation of the unfolded protein response, resulting in concomitant expression of proliferation, prosurvival, and proapoptotic downstream effectors. Consequently, VWM cells are constitutively predisposed and hyperreactive to stress. In view of the fact that VWM genes are housekeeping genes, it is surprising that the disease is primarily a leukoencephalopathy. The pathophysiology of selective glial vulnerability in VWM remains poorly understood.

Leukodystrophies: classification, diagnosis, and treatment

BACKGROUND

The leukodystrophies are a heterogeneous group of diseases, which primarily affect white matter. Symptomatic patients are frequently misdiagnosed and the leukodystrophies are collectively under recognized. However, with ongoing research and increased availability of neuroimaging, our understanding of these diseases is increasing at a steady rate. Recent advances in the diagnosis and treatment of certain forms of leukodystrophy should prompt increased awareness of these diseases in clinical practice.

REVIEW SUMMARY

The clinical features, pathophysiology, and therapeutic approach to these diseases are described. Particular emphasis is placed on genetic and pathophysiologic mechanisms, imaging patterns, screening of other family members and, where available, treatment options and resources.

CONCLUSIONS

With more widespread use of neuroimaging, both pediatric and adult neurologists will increasingly be confronted with white matter disorders. Neurologists should have an approach to the recognition, diagnosis, and management of white matter diseases in general and the leukodystrophies in specific.

Natural history of adult-onset eIF2B-related disorders: a multi-centric survey of 16 cases

Mutations in one of the five eukaryotic initiation factor 2B genes (EIF2B1-5) were first described in childhood ataxia with cerebral hypomyelination--vanishing white matter syndrome. The syndrome is characterized by (i) cerebellar and pyramidal signs in children aged 2-5 years; (ii) extensive cavitating leucoencephalopathy; and (iii) episodes of rapid deterioration following stress. Since then a broad clinical spectrum from congenital to adult-onset forms has been reported, leading to the concept of eIF2B-related disorders. Our aim was to describe clinical and brain magnetic resonance imaging characteristics, genetic findings and natural history of patients with adult-onset eIF2B-related disorders (after age 16). The inclusion criteria were based on the presence of eIF2B mutations and a disease onset after the age of 16 years. One patient with an asymptomatic diagnosis (age 16 years) was also included. Clinical and magnetic resonance findings were retrospectively recorded in all patients. All patients were examined to assess clinical evolution, using functional, pyramidal, cerebellar and cognitive scales. This multi-centric study included 16 patients from 14 families. A sex ratio imbalance was noted (male/female = 3/13). The mean age of onset was 31.1 years (range 16-62). Initial symptoms were neurologic (n = 11), psychiatric (n = 2) and ovarian failure (n = 2). Onset of the symptoms was linked to a precipitating factor in 13% of cases that included minor head trauma and delivery. During follow-up (mean: 11.2 years, range 2-22 years) 12.5% of the patients died. Of the 14 survivors, 62% showed a decline in their cognitive functions, and 79% were severely handicapped or bedridden. One case remained asymptomatic. Stress worsened clinical symptoms in 38% of the patients. Magnetic resonance imaging findings consist of constant cerebral atrophy, extensive cystic leucoencephalopathy (81%), corpus callosum (69%) and cerebellar (38%) T2-weighted hyperintensities. All families except one showed mutations in the EIF2B5 gene. The recurrent p.Arg113His-eIF2Bepsilon mutation was found in 79% of the 14 eIF2B-mutated families, mainly at a homozygous state. The family with a mutation in EIF2B2 had the relatively prevalent p.Glu213Gly mutation. eIF2B-related disorder is probably underestimated as an adult-onset inherited leucoencephalopathy. In this late-onset form, presentation ranges from neurologic symptoms to psychiatric manifestations or primary ovarian failure. Cerebral atrophy is constant, whereas the typical vanishing of the white matter can be absent. Functional and/or cognitive prognosis remains severe. Molecular diagnosis is facilitated for these forms by the screening of the two recurrent p.Arg113His-eIF2Bepsilon and p.Glu213Gly-eIF2Bbeta mutations, positive in 86% of cases.

The ovarioleukodystrophy

The "ovarioleukodystrophies" comprise a group of rare leukodystrophies associated with primary or premature ovarian failure. Some of the patients have a variant of "vanishing white matter disease" with mutations in subunits of eukaryotic initiation factor 2B (EIF2B). A 32-year-old woman who developed neurological signs related to an extensive leukoencephalopathy on magnetic resonance imaging (MRI) in the context of amenorrhea since the age of 18 years was found to be homozygous for a mutation in the EIF2B5 gene: c.338G>A/p.Arg113His. She had a progressive disease with development of tetraparesia in less than 6 years. Our observation confirms that ovarian failure in the context of a leukodystrophy warrants mutational analysis of the genes encoding the subunits of EIF2B.

Sensitivity and specificity of decreased CSF asialotransferrin for eIF2B-related disorder

OBJECTIVE

This is a study estimating diagnostic accuracy of CSF asialotransferrin to transferrin ratio measurement in eIF2B related disorders by using clinical evaluation and EIF2B mutation analysis as the reference standard. eIF2B-related disorder is a relatively common leukodystrophy with broad phenotypic variation that is caused by mutations in any of the five EIF2B genes. There is a need for a simple and clinically valid screening tool for physicians evaluating patients with an unclassified leukodystrophy.

METHODS

CSF two-dimensional gel (2DG) electrophoresis analyses to measure asialotransferrin to transferrin ratios were performed in 60 subjects including 6 patients with documented EIF2B gene mutations, patients with other types of leukodystrophy, and patients with no leukodystrophy.

RESULTS

All six patients with mutation proven eIF2B-related disease showed low to nearly undetectable amounts of asialotransferrin in their CSF when compared to 54 unaffected controls by CSF 2DG analyses in this study. eIF2B-like patients, with clinically similar presentations but no mutations in EIF2B1-5, were distinguished from patients with mutations in EIF2B1-5 by this biomarker. Patients with mutations in EIF2B1-5 had asialotransferrin/transferrin ratio levels significantly different from the group as a whole (p < 0.001). Using 8% asialotransferrin/transferrin ratio as a cutoff, this biomarker has a 100% sensitivity (95% CI = 52-100%) and 94% specificity (95% CI = 84-99%).

CONCLUSION

Decreased asialotransferrin/transferrin ratio in the CSF of patients with eIF2B-related disorder is highly sensitive and specific. This rapid (<48 hours) and inexpensive diagnostic tool for eIF2B-related disorders has the potential to identify patients with likely eIF2B-related disorder for mutation analysis.

Acute neurological deterioration in ovarioleukodystrophy related to EIF2B mutations: pregnancy with oocyte donation is a potentially precipitating factor

Mutations in the eukaryotic translation initiation factor 2B (eIF2B) represent a heterogenous group of autosomal recessive leucodystrophy characterized by a diffuse CSF-like aspect of the white matter at MRI designed as vanishing white matter (VWM) and episodes of acute deterioration after stresses. The mild juvenile and adult forms are often associated with primary ovarian failure, a syndrome referred to as ovarioleukodystrophy (OLD). We reported case of a woman with OLD who successfully underwent in vitro fertilization with donated oocytes and embryo transfer. Pregnancy was complicated by a non-convulsive epileptic status leading to the identification of compound heterozygous EIF2B5 mutation (p.Arg113His and p.Arg299His). The patient gave birth to a healthy child by Caesarean section. In conclusion, we report for the first time that in vitro fertilization and embryo transfer can lead to a successful procreation in patients with OLD related to EIF2B mutations. However this procedure must be considered with cautiousness, because of its potential neurological risks.

Immune response in leukodystrophies

Although the genetics and biochemistry of leukodystrophies have been extensively explored, the immune response in these disorders has received relatively little attention. Both the disease course and its response to treatment may be highly dependent on the immune system. In this review, we compare three common leukodystrophies, each with a different immune response: (1) X-linked adrenoleukodystrophy, which demonstrates a severe, lymphocytic inflammatory response; (2) metachromatic leukodystrophy, which yields a histiocytic response; and (3) vanishing white-matter disease, in which no inflammation is typically seen. We highlight the biochemical, pathologic, and clinical differences, while focusing on the immune response in each disease. We also review the response of leukodystrophies to immunomodulatory therapies and interventions such as hematopoietic stem-cell transplantation. Future studies may delineate specific inflammatory markers as possible candidates for therapeutic intervention.

Le syndrome CACH/VWM et les leucodystrophies liées à des mutations EIF2B

A new leukoencephalopathy, the CACH syndrome (Childhood Ataxia with Central nervous system Hypomyelination) or VWM (Vanishing White Matter) was identified on clinical and MRI criteria. Classically, this disease is characterized by (1) an onset between 2 and 5 years of age, with a cerebello-spastic syndrome exacerbated by episodes of fever or head trauma leading to death after 5 to 10 years of disease evolution, (2) a diffuse involvement of the white matter on cerebral MRI with a CSF-like signal intensity (cavitation), (3) a recessive autosomal mode of inheritance, (4) neuropathologic findings consistent with a cavitating orthochromatic leukodystrophy with increased number of oligodendrocytes with sometimes "foamy" aspect. A total of 148 cases have been reported so far. This disease is linked to mutations in the five EIF2B genes encoding the five subunits of the eukaryotic initiation factor 2B (eIF2B), involved in the protein synthesis and its regulation under cellular stresses. Clinical symptoms are variable, from fatale infantile forms (Cree leukoencephalopathy) and congenital forms associated with extra-neurological affections, to juvenile and adult forms (ovarioleukodystrophy) characterized by cognitive and behaviour dysfunctions and by a slow progression of the disease, leading to the term of eIF2B-related leukoencephalopathies. Prevalence of these remains unknown. Diagnosis lays on the detection of EIF2B mutations, affecting predominantly the EIF2B5 gene. A decrease in the intrinsic activity of the eIF2B factor (the guanine exchange activity, GEF) in lymphoblasts from patients seems to have a diagnostic value. The patho-physiology of the disease would involve a deficiency in astrocytes maturation leading to an increased susceptibility of the white matter to cellular stress. No specific treatment exists except the "prevention" of cellular stress. Corticosteroids sometimes proved to be useful in acute phases. Prognosis seems to correlate with the age of onset, the earliest forms being more severe.

Leukodystrophies: clinical and genetic aspects

The leukodystrophies comprise an ever-expanding group of rare central nervous system disorders with defined clinical, pathological, and genetic characteristics. The broader term, leukoencephalopathy, is applied to all brain white matter diseases, whether their molecular cause is known. Magnetic resonance imaging has helped to elucidate new forms of leukodystrophy as well as to permit longitudinal studies of disease progression. The white matter abnormality may appear similar in different forms of leukodystrophy so that in most cases, further studies such as magnetic resonance spectroscopy, tissue biopsies, enzyme studies, and molecular DNA analyses are needed to pinpoint the specific diagnosis. The primary inherited leukoencephalopathies include dysmyelinating, hypomyelinative, and vacuolating forms. Metabolic and vascular causes account for most of the secondary forms, but other inherited syndromes are recognized that have their onset in childhood or adult life and are characterized by distinctive clinical and neuropathologic features. This review discusses some of the mechanisms that have been proposed to explain deficiencies of myelin and the molecular genetic bases underlying these disorders.

Vanishing white matter disease

Vanishing white matter disease (VWM) is one of the most prevalent inherited childhood leucoencephalopathies. The classical phenotype is characterised by early childhood onset of chronic neurological deterioration, dominated by cerebellar ataxia. VWM is unusual because of its clinically evident sensitivity to febrile infections, minor head trauma, and acute fright, which may cause rapid neurological deterioration and unexplained coma. Most patients die a few years after onset. The phenotypic variation is extremely wide, including antenatal onset and early demise and adult-onset, slowly progressive disease. MRI findings are diagnostic in almost all patients and are indicative of vanishing of the cerebral white matter. The basic defect of this striking disease resides in either one of the five subunits of eukaryotic translation initiation factor eIF2B. eIF2B is essential in all cells of the body for protein synthesis and its regulation under different stress conditions. Although the defect is in housekeeping genes, oligodendrocytes and astrocytes are predominantly affected, whereas other cell types are surprisingly spared. Recently, undue activation of the unfolded-protein response has emerged as important in the pathophysiology of VWM, but the selective vulnerability of glia for defects in eIF2B is poorly understood.

Childhood ataxia with CNS hypomyelination/vanishing white matter disease--a common leukodystrophy caused by abnormal control of protein synthesis

Mutations in eukaryotic initiation factor 2B (eIF2B) cause one of the most common leukodystrophies, childhood ataxia with CNS hypomyelination/vanishing white matter disease or CACH/VWM. Patients may develop a wide spectrum of neurological abnormalities from prenatal-onset white matter disease to juvenile or adult-onset ataxia and dementia, sometimes with ovarian insufficiency. The pattern of diffuse white matter abnormalities on MRI of the head is often diagnostic. Neuropathological abnormalities indicate a unique and selective disruption of oligodendrocytes and astrocytes with sparing of neurons. Marked decrease of asialo-transferrin in cerebrospinal fluid is the only biochemical abnormality identified thus far. Eukaryotic translation initiation factor 2B (eIF2B) mutations cause a decrease in guanine nucleotide exchange activity on eIF2-GDP, resulting in increased susceptibility to stress and enhanced ATF4 expression during endoplasmic reticulum stress. eIF2B mutations are speculated to lead to increased susceptibility to various physiological stress conditions. Future research will be directed towards understanding why abnormal control of protein translation predominantly affects brain glial cells.

Defective translation initiation causes vanishing of cerebral white matter

Leukoencephalopathy with vanishing white matter (VWM) is one of the most prevalent inherited white-matter disorders, especially in Caucasian populations. VWM is unusual because of its sensitivity to febrile infections and minor head trauma. The basic defect of this enigmatic brain disease resides in the regulation of initiation of protein synthesis. Recently, undue activation of the unfolded-protein response has emerged as an important factor in the pathophysiology of VWM. Here, we discuss the mechanisms that might be responsible for the selective involvement of the brain white matter in VWM. At present, VWM research is in need of an animal model to study disease mechanisms and therapeutic interventions.

Heightened stress response in primary fibroblasts expressing mutant eIF2B genes from CACH/VWM leukodystrophy patients

Childhood ataxia with central nervous system hypomyelination (CACH), also called vanishing white matter (VWM) leukoencephalopathy, is a fatal genetic disease caused by mutations in eukaryotic initiation factor 2B (eIF2B) genes. The five subunits eIF2B factor is critical for translation initiation under normal conditions and regulates protein synthesis in response to cellular stresses. Primary fibroblasts from CACH/VWM patients and normal individuals were used to measure basal eIF2B activity as well as global protein synthesis and ATF4 induction in response to stress in the endoplasmic reticulum. We show that although the cells expressing mutant eIF2B genes respond normally to stress conditions by reduced global translation rates, they exhibit significantly greater increase in ATF4 induction compared to normal controls despite equal levels of stress and activity of the upstream eIF2alpha kinase. This heightened stress response observed in primary fibroblasts that suffer from minor loss of basal eIF2B activity may be employed as an initial screening tool for CACH/VWM leukodystrophy.

Premature ovarian failure

Premature ovarian failure (POF) causing hypergonadotrophic hypogonadism occurs in 1% of women. In majority of cases the underlying cause is not identified. The known causes include: (a) Genetic aberrations, which could involve the X chromosome or autosomes. A large number of genes have been screened as candidates for causing POF; however, few clear causal mutations have been identified. (b) Autoimmune ovarian damage, as suggested by the observed association of POF with other autoimmune disorders. Anti-ovarian antibodies are reported in POF by several studies, but their specificity and pathogenic role are questionable. (c) Iatrogenic following surgical, radiotherapeutic or chemotherapeutic interventions as in malignancies. (d) Environmental factors like viral infections and toxins for whom no clear mechanism is known. The diagnosis is based on finding of amenorrhoea before age 40 associated with FSH levels in the menopausal range. Screening for associated autoimmune disorders and karyotyping, particularly in early onset disease, constitute part of the diagnostic work-up. There is no role of ovarian biopsy or ultrasound in making the diagnosis. Management essentially involves hormone replacement and infertility treatment, the only proven means for the latter being assisted conception with donated oocytes. Embryo cryopreservation, ovarian tissue cryopreservation and oocyte cryopreservation hold promise in cases where ovarian failure is foreseeable as in women undergoing cancer treatments.

Dominant form of vanishing white matter-like leukoencephalopathy

Leukoencephalopathy with vanishing white matter syndrome (childhood ataxia with central nervous system hypomyelination/vanishing white matter disease) is an autosomal recessive disorder characterized by the occurrence of acute episodes of deterioration after minor head trauma or infection, and symmetrical demyelination on magnetic resonance with cavitation aspects. Mutations in each of the five subunits of eIF2B have been identified. We report in an affected man and his mother an adult-onset form of childhood ataxia with central nervous system hypomyelination/vanishing white matter disease-like disorder with no mutations in the EIF2B genes and normal guanine nucleotide exchange factor eIF2B activity, suggesting a new dominant inheritance of this syndrome that may involve other genes.

The effect of genotype on the natural history of eIF2B-related leukodystrophies

BACKGROUND

Recessive mutations in the five eucaryotic initiation factor 2B (eIF2B) subunits have been found in leukodystrophies of variable age at onset and severity.

OBJECTIVES

To evaluate the clinical spectrum of eIF2B-related disorders and search for a phenotype-genotype correlation.

METHODS

Ninety-three individuals (78 families) with an undetermined leukodystrophy were selected on MRI-based criteria of childhood ataxia with central hypomyelination/vanishing white matter (CACH/VWM) for EIF2B genes analysis.

RESULTS

Eighty-nine percent of individuals with MRI criteria of CACH/VWM have a mutation in one of the eIF2B beta to epsilon subunits. For 83 individuals (68 families), 46 distinct mutations (90% missense) in four of the five eIF2B subunits (beta, gamma, delta, epsilon) were identified. Sixty-four percent were in the epsilon subunit, a R113H substitution was found in 71% of eIF2B epsilon-mutated families. A large clinical spectrum was observed from rapidly fatal infantile to asymptomatic adult forms. Disease severity was correlated with age at onset (p < 0.0001) but not with the type of the mutated subunit nor with the position of the mutation within the protein. Mutations R113H in the epsilon subunit and E213G in the beta subunit were significantly associated with milder forms.

CONCLUSIONS

The degree of eIF2B dysfunction, which is involved in the regulation of protein synthesis during cellular stress, may play a role in the clinical expression of eIF2B-related disorders.

The latest on leukodystrophies

PURPOSE OF REVIEW

Important advances in our understanding of genetic disorders of the white matter have been made and are discussed here.

RECENT FINDINGS

It has recently been discovered that mutations in the genes encoding the five subunits of eukaryocytic initiation factor 2B (eIF2B) are the cause of vanishing white-matter disease/childhood ataxia with central hypomyelination syndrome. The extension of the clinical features of the eIF2B-related disorders to encompass both infant- and adult-onset disorders is discussed. New clinico-imaging syndromes such as hypomyelination with atrophy of the basal ganglia and cerebellum and leukoencephalopathy with brain-stem and spinal cord involvement and elevated white-matter lactate are described. Recent findings include evidence that mitochondrial fat-oxidation abnormalities may be important in the pathogenesis of adrenoleukodystrophy, and that a mutant myelin protein can cause maldistribution of other myelin proteins, causing dysmyelination, axonal damage, or both.

SUMMARY

This review focuses on advances in the understanding of the role of eIF2B as a cause of a common leukodystrophy syndrome. eIF2B-related disorders have a clinical spectrum ranging from a severe, rapidly progressive congenital or early infantile encephalopathy to a slowly progressive cognitive and motor deterioration often associated with premature ovarian failure. Two newly recognized leukodystrophy syndromes are described: hypomyelination with atrophy of the basal ganglia and cerebellum, and leukoencephalopathy with brain-stem and spinal cord involvement and elevated white-matter lactate. An update is also given for adrenoleukodystrophy and myelin-protein-related disorders. This update demonstrates that an increasing number of genetic defects are being identified that may cause primary white-matter disorders.

Ovarian failure related to eukaryotic initiation factor 2B mutations

Ovarian failure (OF) at age <40 years occurs in approximately 1% of all women. Other than karyotype abnormalities, very few genes are known to be associated with this ovarian dysfunction. We studied eight patients who presented with premature OF and white-matter abnormalities on magnetic resonance imaging. Neurological signs may be absent or present after OF. In seven patients, we report for the first time mutations in three of the five EIF2B genes (EIF2B2, -4, and -5) that were recently shown to cause childhood ataxia with central nervous system hypomyelination/vanishing white-matter disease leukodystrophy. The correlation we observed between the age at onset of the neurological deterioration and the severity of OF suggests a common pathophysiological pathway.

Adult onset pigmentary orthochromatic leukodystrophy with ovarian dysgenesis

Pigmentary type of orthochromatic leukodystrophy (POLD) is an adult-onset leukodystrophy, characterized pathologically by the presence of glial and microglial cytoplasmic pigment inclusions. The complete phenotype, genotype and pathogenetic mechanisms in POLD have not been elucidated. We followed for 18 years a woman with autopsy-proven POLD, who presented with 'frontal' dementia and spasticity. Her further course was marked by progressive mutism, apraxia and seizures. Her sister had died of the same disease after a much more rapidly progressing course. These sisters had primary infertility with pathologic evidence of streak ovaries. Diagnosis was confirmed in both cases by post-mortem examination. POLD is a rare cause of adult-onset leukodystrophy presenting with dementia. Ovarian dysgenesis is extremely rare in the absence of demonstrable chromosomal abnormalities and extends the clinical spectrum of POLD.

Spectroscopic imaging of radiation-induced effects in the white matter of glioma patients

External radiation therapy of brain tumors may cause adverse effects on normal brain tissue, resulting in severe neuropsychological and cognitive impairment. We investigated the late delayed radiation effects in the white matter (WM) using (1)H magnetic resonance spectroscopic imaging ((1)HMRSI). Nine glioma patients with local radiation-induced signal abnormalities in the T(2)-weighted MR images were studied with nine age- and sex-matched controls. The metabolite ratios in the radiation-induced hyper intensity area (RIHA) and in the normal appearing white matter (NAWM) of the patients were compared with respective WM areas of the controls. In RIHA, choline/creatine (Cho/Cr) was 17% decreased (1.22 +/- 0.13 vs 1.47 +/- 0.16, p = 0.0027, significant (s), unpaired Student's t test with Bonferroni correction) in the patients compared to the controls, while there was no difference in N-acetyl aspartate/Cr (NAA/Cr) (2.49 +/- 0.57 vs 2.98 +/- 0.32, p = 0.039) or NAA/Cho (2. 03 +/- 0.40 vs 2.04 +/- 0.17, p = 0.95). In NAWM, Cho/Cr was 24% decreased (1.21 +/- 0.15 vs 1.59 +/- 0.13, p < 0.0001, s) and NAA/Cho was 20% increased (2.49 +/- 0.49 vs 1.98 +/- 0.15, p = 0. 0082, s) in the patients compared to the controls, while there was no difference in NAA/Cr (2.99 +/- 0.46 vs 3.16 +/- 0.32, p = 0.38). NAA(RIHA)/NAA(NAWM) was 25% decreased (0.75 +/- 0.20 vs 1.00 +/- 0. 12, p = 0.0043, s) and Cr(RIHA)/Cr(NAWM) was 16% decreased (0.89 +/- 0.15 vs 1.06 +/- 0.10, p = 0.013, s) in the patients compared to the controls, while there was no difference in Cho(RIHA)/Cho(NAWM) (0.92 +/- 0.23 vs 0.98 +/- 0.10, p = 0.47). (1)HMRSI reveals widespread chemical changes in the WM after radiation therapy. In RIHA, there is loss of NAA, Cho, and Cr implying axonal and membrane damage and in NAWM, there is loss of Cho, reflecting membrane damage.