Molecular findings in symptomatic and pre-symptomatic Alexander disease patients

Alexander disease: The story behind an eponym

In 1949, William Stewart Alexander (1919-2013), a young pathologist from New Zealand working in London, reported the neuropathological findings in a 15-month-old boy who had developed normally until the age of seven months, but thereafter had progressive enlargement of his head and severe developmental delay. The most striking neuropathological abnormality was the presence of numerous Rosenthal fibers in the brain. The distribution of these fibers suggested to Alexander that the primary pathological change involved astrocytes. In the next 15 years, five similar patients were reported, and in 1964 Friede recognized these cases reflected a single disease process and coined the eponym "Alexander's disease" to describe the disorder. In the 1960s, electron microscopy confirmed that Rosenthal fibers were localized to astrocytes. In 2001, it was shown that Alexander disease is caused by mutations in the gene encoding glial fibrillary acidic protein, the major intermediate filament protein in astrocytes. Although the clinical, imaging, and pathological manifestations of Alexander disease are now well known, few people are familiar with Alexander's career. Although he did not make a further contribution to the literature on Alexander disease, his observations and accurate interpretation of the neuropathology have justified the continued use of the eponym "Alexander disease."

Adult-onset Alexander disease among patients of Jewish Syrian descent

Alexander disease (AxD) is a rare autosomal dominant leukodystrophy caused by heterozygous mutations in the glial fibrillary acid protein (GFAP) gene. The age of symptoms onset ranges from infancy to adulthood, with variable clinical and radiological manifestations. Adult-onset AxD manifests as a chronic and progressive condition, characterized by bulbar, motor, cerebellar, and other clinical signs and symptoms. Neuroradiological findings typically involve the brainstem and cervical spinal cord. Adult-onset AxD has been described in diverse populations but is rare in Israel. We present a series of patients diagnosed with adult-onset AxD from three families, all of Jewish Syrian descent. Five patients (4 females) were diagnosed with adult-onset AxD due to the heterozygous mutation c.219G > A, p.Met73Ile in GFAP. Age at symptoms onset ranged from 48 to 61 years. Clinical characteristics were typical and involved progressive bulbar and gait disturbance, followed by pyramidal and cerebellar impairment, dysautonomia, and cognitive decline. Imaging findings included medullary and cervical spinal atrophy and mostly infratentorial white matter hyperintensities. A newly recognized cluster of adult-onset AxD in Jews of Syrian origin is presented. This disorder should be considered in differential diagnosis in appropriate circumstances. Genetic counselling for family members is required in order to discuss options for future family planning.

The N-Terminal Part of the 1A Domain of Desmin Is a Hot Spot Region for Putative Pathogenic DES Mutations Affecting Filament Assembly

Desmin is the major intermediate filament protein of all three muscle cell types, and connects different cell organelles and multi-protein complexes such as the cardiac desmosomes. Several pathogenic mutations in the DES gene cause different skeletal and cardiac myopathies. However, the significance of the majority of DES missense variants is currently unknown, since functional data are lacking. To determine whether desmin missense mutations within the highly conserved 1A coil domain cause a filament assembly defect, we generated a set of variants with unknown significance and systematically analyzed the filament assembly using confocal microscopy in transfected SW-13, H9c2 cells and cardiomyocytes derived from induced pluripotent stem cells. We found that mutations in the N-terminal part of the 1A coil domain affect filament assembly, leading to cytoplasmic desmin aggregation. In contrast, mutant desmin in the C-terminal part of the 1A coil domain forms filamentous structures comparable to wild-type desmin. Our findings suggest that the N-terminal part of the 1A coil domain is a hot spot for pathogenic desmin mutations, which affect desmin filament assembly. This study may have relevance for the genetic counselling of patients carrying variants in the 1A coil domain of the DES gene.

Identification of a novel de novo pathogenic variant in GFAP in an Iranian family with Alexander disease by whole-exome sequencing

Background

Alexander disease (AxD) is a rare leukodystrophy with an autosomal dominant inheritance mode. Variants in GFAP lead to this disorder and it is classified into three distinguishable subgroups: infantile, juvenile, and adult-onset types.

Objective

The aim of this study is to report a novel variant causing AxD and collect all the associated variants with juvenile and adult-onset as well.

Methods

We report a 2-year-old female with infantile AxD. All relevant clinical and genetic data were evaluated. Search strategy for all AxD types was performed on PubMed. The extracted data include total recruited patients, number of patients carrying a GFAP variant, nucleotide and protein change, zygosity and all the clinical symptoms.

Results

A novel de novo variant c.217A > G: p. Met73Val was found in our case by whole-exome sequencing. In silico analysis categorized this variant as pathogenic. Totally 377 patients clinically diagnosed with juvenile or adult-onset forms were recruited in these articles, among them 212 patients were affected with juvenile or adult-onset form carrier of an alteration in GFAP. A total of 98 variants were collected. Among these variants c.262C > T 11/212 (5.18%), c.1246C > T 9/212 (4.24%), c.827G > T 8/212 (3.77%), c.232G > A 6/212 (2.83%) account for the majority of reported variants.

Conclusion

This study highlighted the role of genetic in AxD diagnosing. It also helps to provide more information in order to expand the genetic spectrum of Iranian patients with AxD. Our literature review is beneficial in defining a better genotype–phenotype correlation of AxD disorder.

Neuroimaging Pearls from the MDS Congress Video Challenge. Part 1: Genetic Disorders

We selected several "imaging pearls" presented during the Movement Disorder Society (MDS) Video Challenge for this review. While the event, as implicated by its name, was video-centered, we would like to emphasize the important role of imaging in making the correct diagnosis. We divided this anthology into two parts: genetic and acquired disorders. Genetic cases described herein were organized by the inheritance pattern and the focus was put on the imaging findings and differential diagnoses. Despite the overlapping phenotypes, certain described disorders have pathognomonic MRI brain findings that would provide either the "spot" diagnosis or result in further investigations leading to the diagnosis. Despite this, the diagnosis is often challenging with a broad differential diagnosis, and hallmark findings may be present for only a limited time.

[Alexander disease: diversity of cell population and interactions between neuron and glia]

Alexander disease (AxD) is a rare neurodegenerative disorder caused by the mutations in glial fibrillary acidic protein (GFAP) gene. Rosenthal fiber formations in astrocytes are the pathological hallmarks of AxD. Astrocyte dysfunction in the AxD brain is considered to be involved in its pathogenesis. We have previously reported that in AxD model mice aberrant Ca²⁺ signals in astrocytes were associated with the upregulation of reactive phenotype. Reactive astrocytes are conditions that lead to morphological, functional, and molecular changes by responding to various pathological insults (trauma, inflammation, ischemia), and environmental stimuli. Recent technological advances in single-cell gene expression analysis have revealed that astrocytes have heterogeneity by indicating that they form sub population with different characteristics depending on the brain region, the growth development, aging stage, and the pathological condition. AxD astrocytes are also thought to constitute a heterogeneous population with diverse properties and functions. Moreover, it is presumed that AxD pathogenesis occur due to interactions with neurons and other glial cells, as well as the microenvironment in tissues. Research strategies based on these perspectives will help us understand AxD pathology better and may lead to the elucidation of disease modifiers and clinical diversity.

GFAP variants leading to infantile Alexander disease: Phenotype and genotype analysis of 135 cases and report of a de novo variant

OBJECTIVES

Alexander disease (AxD) is a rare autosomal dominant disorder due to GFAP mutations; infantile AxD is the most common severe form which usually results in death. In this study, phenotype and genotype analysis of all reported cases with IAxD are reported as well as a de novo variant.

METHODS

We conduct a comprehensive review on all reported Infantile AxD due to GFAP mutation. Clinical data and genetics of the reported patients were analyzed. Clinical evaluations, pedigree drawing, MRI and sequencing of GFAP were performed.

RESULTS

135 patients clinically diagnosed with IAxD had GFAP mutations. A total of fifty three variants of GFAP were determined; 19 of them were located at 1A domain. The four common prevalent variants (c 0.715C>T, c 0.236G˃A, c 0.716G˃A, and c 0.235C˃T) were responsible for 64/135 (47.4%) of the patients. Seizure was the dominant clinical symptom (62.3%) followed by macrocephaly (41%), developmental delay (23.9%) and spasticity (23.9%). A de novo variant c 0.715C˃T was found in the presented Iranian case.

DISCUSSION

The majority of GFAP variant are located in a specific domain of the protein. Seizure as the most common symptom of IAxD could be considered. This study highlighted the role of genetic testing for diagnosing AxD.

Neuropsychological Functioning in Alexander Disease: A Case Series

Limited information is known about neuropsychological outcomes in Alexander disease, a rare leukodystrophy. Two pediatric cases are summarized. Case 1 (evaluations at 6, 7, 9, and 12 years of age) represents Type I Alexander disease with associated seizures. Case 2 (evaluations at 12, 13, and 16 years of age) represents Type II Alexander disease without additional complications. Case 1 experienced declines in intellectual functioning, visual motor skills, receptive vocabulary, verbal memory, and academic achievement. Case 2 experienced variable neurocognitive change and academic functioning, with average word reading and spelling. Verbal memory also remained intact. Taken together, individuals with Alexander disease may experience cognitive decline to variable degrees. Type I Alexander disease, associated with earlier onset and additional neurological complications, may presage greater cognitive decline than Type II. Due to variability in functioning over time, it is critical to follow individuals across development to make recommendations for educational and treatment planning.

[A case of Alexander disease presented with dystonia of lower limb and decreased dopaminergic uptake in dopamine transporter scintigraphy]

A 50-year-old woman developed gait disturbances and dysarthria since the past 2 years. She also presented with dystonia and hypokinesia of her left lower limb, and orthostatic hypotension. The dopamine transporter SPECT with ¹²³I ioflupane showed abnormal scans in bilateral striatum. Cerebral MRI revealed atrophy and signal changes in the medulla and spinal cord, from which Alexander disease (AxD) was suspected. Consequently, we checked the Glial fibrillary acidic protein (GFAP) gene. The analysis of the gene detected a heterozygous c.219G>T mutation, which was the first mutation reported in Japan, and finally she was diagnosed with AxD. Dystonia is relatively rare in AxD patients, but this case demonstrated that AxD should be listed in the differential diagnosis of extrapyramidal syndromes with abnormalities of the medulla and spinal cord on MRI.

Recessively-Inherited Adult-Onset Alexander Disease Caused by a Homozygous Mutation in the GFAP Gene

BACKGROUND

Alexander disease (AxD) is an autosomal-dominant leukodystrophy caused by heterozygous mutations in the glial fibrillary acidic protein (GFAP) gene.

OBJECTIVES

The objective of this report is to characterize the clinical phenotype and identify the genetic mutation associated with adult-onset AxD.

METHODS

A man presented with progressive unsteadiness since age 16. Magnetic resonance imaging findings revealed characteristic features of AxD. The GFAP gene was screened, and a candidate variant was functionally tested to evaluate causality.

RESULTS

A homozygous c.197G > A (p.Arg66Gln) mutation was found in the proband, and his asymptomatic parents were heterozygous for the same mutation. This mutation affected GFAP solubility and promoted filament aggregation. The presence of the wild-type protein rescued mutational effects, consistent with the recessive nature of this mutation.

CONCLUSIONS

This study is the first report of AxD caused by a homozygous mutation in GFAP. The clinical implication is while examining patients with characteristic features on suspicion of AxD, GFAP screening is recommended even without a supportive family history. © 2020 International Parkinson and Movement Disorder Society.

A case report of adult-onset Alexander disease clinically presenting as Parkinson's disease: is the comorbidity associated with genetic susceptibility?

Background

Alexander disease is a rare neurological disease characterized by progressive spastic quadriparesis and bulbar palsy. Moreover, certain patients with adult-onset Alexander disease were often misdiagnosed as other neurodegenerative disorders.

Case presentation

Herein, we report an adult a 58-year-old woman presented with typical parkinsonism with good levodopa-responsiveness. The patient’s dopamine transporter scanning showed significant striatal depletion, while her brain magnetic resonance imaging revealed bilateral tadpole shape of medulla oblongata and bilateral high signal intensity at both cerebellar dentate nuclei in T2-weighted images, suggesting the possibility of a genetic disorder beyond Parkinson’s disease. The patient’s genetic test resulted in known pathogenic glial fibrillary acidic protein variant, indicating Alexander disease.

Conclusion

This unique case highlights genetically diagnosed Alexander disease may present with clinical Parkinson’s disease.

Infantile Alexander Disease with Late Onset Infantile Spasms and Hypsarrhythmia

Alexander disease (AxD) is a rare autosomal dominant leukodystrophy with three clinical subtypes: infantile, juvenile and adult. Forms differ by age of symptoms occurrence and the clinical presentation. Although recent data suggest considering only two subtypes: type I (infantile onset with lesions extending to the cerebral hemispheres); type II (adult onset with primary involvement of subtentorial structures). Dominant mutations in the glial fibrillary acidic protein (GFAP) gene in AxD cause dysfunction of astrocytes (a type III intermediate filament). The authors discuss the clinical picture of a boy with infantile form of AxD confirmed by the presence of de novo heterozygous mutation c.236G>A in the GFAP gene and without striking symptoms such as macrocephaly and with exceptional late-onset epileptic spasms with hypsarrhyth- mia on electroencephalogram (EEG).

A Novel Mutation of GFAP Causing Adult-Onset Alexander Disease

Alexander disease (AxD) is a rare, autosomal dominant neurological disorder. Three clinical subtypes are distinguished based on age at onset: infantile (0–2 years), juvenile (2–13 years), and adult (>13 years). The three forms differ in symptoms and prognosis. Rapid neurological decline with a fatal course characterizes the early-onset forms, while symptoms are milder and survival is longer in the adult forms. Currently, the sole known cause of AxD is mutations in the GFAP gene, which encodes a type III intermediate filament protein that is predominantly expressed in astrocytes. A wide spectrum of GFAP mutations comprising point mutations, small insertions, and deletions is associated with the disease. The genotype-phenotype correlation remains unclear. The considerable heterogeneity in severity of disease among individuals carrying identical mutations suggests that other genetic or environmental factors probably modify age at onset or progression of AxD. Describing new cases is therefore important for establishing reliable genotype-phenotype correlations and revealing environmental factors able to modify age at onset or progression of AxD. We report the case of a 54-year-old Caucasian woman, previously diagnosed with ovarian cancer and treated with surgery and chemotherapy, who developed dysarthria, ataxia, and spastic tetraparesis involving mainly the left side. Cerebral and spinal magnetic resonance imaging (MRI) revealed a peculiar tadpole-like atrophy of the brainstem. Genetic analysis of the GFAP gene detected a heterozygous mutation in exon 1 (c.219G>C), resulting in an amino acid exchange from methionine to isoleucine at codon 73 (p.M73I). The expression of this mutant in vitro affected the formation of the intermediate filament network. Thus, we have identified a new GFAP mutation in a patient with an adult form of AxD.

Novel GFAP Variant in Adult-onset Alexander Disease With Progressive Ataxia and Palatal Tremor

INTRODUCTION

Alexander disease is a rare neurodegenerative disease caused by variants in the glial fibrillary acidic protein gene (GFAP). This disorder can develop as an infantile, juvenile or adult-onset form and is characterized by several clinical features, including macrocephaly, seizures, ataxia, and bulbar/pseudobulbar signs. While the majority of these patients have the more progressive infantile form which causes severe leukodystrophy and early death; the less common adult form is more variable (ie, onset age, symptoms), with bulbar dysfunction as the primary feature.

CASE REPORT

In our investigation, we describe a patient with progressive neuromuscular issues including dyspnea, dysphagia, dysarthria and progressive ataxia with palatal tremor.

CONCLUSIONS

Through genetic testing, we determined that our patient has a novel variant in GFAP typical of Alexander disease.

A novel three-base duplication, E243dup, of GFAP identified in a patient with Alexander disease

Alexander disease (AxD) is a rare hereditary neurodegenerative disorder caused by glial fibrillary acidic protein (GFAP) gene mutations, most of which are missense mutations. We present an AxD case with a novel de novo three-base duplication mutation in GFAP resulting in E243dup.

Isolation of Intermediate Filament Proteins from Multiple Mouse Tissues to Study Aging-associated Post-translational Modifications

Intermediate filaments (IFs), together with actin filaments and microtubules, form the cytoskeleton - a critical structural element of every cell. Normal functioning IFs provide cells with mechanical and stress resilience, while a dysfunctional IF cytoskeleton compromises cellular health and has been associated with many human diseases. Post-translational modifications (PTMs) critically regulate IF dynamics in response to physiological changes and under stress conditions. Therefore, the ability to monitor changes in the PTM signature of IFs can contribute to a better functional understanding, and ultimately conditioning, of the IF system as a stress responder during cellular injury. However, the large number of IF proteins, which are encoded by over 70 individual genes and expressed in a tissue-dependent manner, is a major challenge in sorting out the relative importance of different PTMs. To that end, methods that enable monitoring of PTMs on IF proteins on an organism-wide level, rather than for isolated members of the family, can accelerate research progress in this area. Here, we present biochemical methods for the isolation of the total, detergent-soluble, and detergent-resistant fraction of IF proteins from 9 different mouse tissues (brain, heart, lung, liver, small intestine, large intestine, pancreas, kidney, and spleen). We further demonstrate an optimized protocol for rapid isolation of IF proteins by using lysing matrix and automated homogenization of different mouse tissues. The automated protocol is useful for profiling IFs in experiments with high sample volume (such as in disease models involving multiple animals and experimental groups). The resulting samples can be utilized for various downstream analyses, including mass spectrometry-based PTM profiling. Utilizing these methods, we provide new data to show that IF proteins in different mouse tissues (brain and liver) undergo parallel changes with respect to their expression levels and PTMs during aging.

Familial Case of Pelizaeus-Merzbacher Disorder Detected by Oligoarray Comparative Genomic Hybridization: Genotype-to-Phenotype Diagnosis

Introduction. Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive hypomyelinating leukodystrophy characterized by nystagmus, spastic quadriplegia, ataxia, and developmental delay. It is caused by mutation in the PLP1 gene. Case Description. We report a 9-year-old boy referred for oligoarray comparative genomic hybridization (OA-CGH) because of intellectual delay, seizures, microcephaly, nystagmus, and spastic paraplegia. Similar clinical findings were reported in his older brother and maternal uncle. Both parents had normal phenotypes. OA-CGH was performed and a 436 Kb duplication was detected and the diagnosis of PMD was made. The mother was carrier of this 436 Kb duplication. Conclusion. Clinical presentation has been accepted as being the mainstay of diagnosis for most conditions. However, recent developments in genetic diagnosis have shown that, in many congenital and sporadic disorders lacking specific phenotypic manifestations, a genotype-to-phenotype approach can be conclusive. In this case, a diagnosis was reached by universal genomic testing, namely, whole genomic array.

Atypical MRI features in familial adult onset Alexander disease: case report

Background

Alexander disease (AxD) is a rare neurological disease, especially in adults. It shows variable clinical and radiological features.

Case presentation

We diagnosed a female with AxD presenting with paroxysmal numbness of the limbs at the onset age of 28-year-old, progressing gradually to spastic paraparesis at age 30. One year later, she had ataxia, bulbar paralysis, bowel and bladder urgency. Her mother had a similar neurological symptoms and died within 2 years after onset (at the age of 47), and her maternal aunt also had similar but mild symptoms at the onset age of 54-year-old. Her brain magnetic resonance imaging (MRI) showed abnormal signals in periventricular white matter with severe atrophy in the medulla oblongata and thoracic spinal cord, and mild atrophy in cervical spinal cord, which is unusual in the adult form of AxD. She and her daughter’s glial fibrillary acidic protein (GFAP) gene analysis revealed the same heterozygous missense mutation, c.1246C > T, p.R416W, despite of no neurological symptoms in her daughter.

Conclusions

Our case report enriches the understanding of the familial adult AxD. Genetic analysis is necessary when patients have the above mentioned symptoms and signs, MRI findings, especially with family history.

Familial Adult-Onset Alexander Disease with a Novel GFAP Mutation

The patient was a 65-year-old woman who became gradually more prone to falling from age 30 and who was visiting the hospital on an outpatient basis following a diagnosis of multiple system atrophy, cerebellar type. While eating, she started choking as a result of aspiration and was transported to our hospital by ambulance. Head magnetic resonance imaging (MRI) revealed tadpole-like atrophy of the brainstem, i.e. marked atrophy of the medulla oblongata and cervical spinal cord with disproportionately slight atrophy of the pons. Her eldest son also had the same symptoms, suggesting Alexander disease. A search of the glial fibrillary acidic protein gene revealed the previously unreported mutation Y242N. The same MRI findings and genetic mutation were confirmed in her 38-year-old son. Adult onset Alexander disease is a rare condition with very few reported familial cases. We hereby report this case with a discussion of the literature.

CSF and Blood Levels of GFAP in Alexander Disease

Alexander disease is a rare, progressive, and generally fatal neurological disorder that results from dominant mutations affecting the coding region of GFAP, the gene encoding glial fibrillary acidic protein, the major intermediate filament protein of astrocytes in the CNS. A key step in pathogenesis appears to be the accumulation of GFAP within astrocytes to excessive levels. Studies using mouse models indicate that the severity of the phenotype correlates with the level of expression, and suppression of GFAP expression and/or accumulation is one strategy that is being pursued as a potential treatment. With the goal of identifying biomarkers that indirectly reflect the levels of GFAP in brain parenchyma, we have assayed GFAP levels in two body fluids in humans that are readily accessible as biopsy sites: CSF and blood. We find that GFAP levels are consistently elevated in the CSF of patients with Alexander disease, but only occasionally and modestly elevated in blood. These results provide the foundation for future studies that will explore whether GFAP levels can serve as a convenient means to monitor the progression of disease and the response to treatment.

Infantile onset alexander disease with normal head circumference: a genetically proven case report

Alexander disease (AD) is an autosomal dominant leukodystrophy which predominantly affects infants and children. The infantile form comprises the most common form of AD. It presents before two years of age and characterized by macrocephaly, psychomotor regression, spasticity, pyramidal sign, ataxia and seizures. The diagnosis is based on magnetic resonance imaging (MRI) findings and confirmed by Glial fibrillary acidic protein (GFAP) gene molecular testing. We report an Indian case with normal head circumference.

A conserved rod domain phosphotyrosine that is targeted by the phosphatase PTP1B promotes keratin 8 protein insolubility and filament organization

Post-translational modifications are important functional determinants for intermediate filament (IF) proteins. Phosphorylation of IF proteins regulates filament organization, solubility, and cell-protective functions. Most known IF protein phosphorylation sites are serines localized in the variable "head" and "tail" domain regions. By contrast, little is known about site-specific tyrosine phosphorylation or its implications on IF protein function. We used available proteomic data from large scale studies to narrow down potential phospho-tyrosine sites on the simple epithelial IF protein keratin 8 (K8). Validation of the predicted sites using a pan-phosphotyrosine and a site-specific antibody, which we generated, revealed that the highly conserved Tyr-267 in the K8 "rod" domain was basally phosphorylated. The charge at this site was critically important, as demonstrated by altered filament organization of site-directed mutants, Y267F and Y267D, the latter exhibiting significantly diminished solubility. Pharmacological inhibition of the protein-tyrosine phosphatase PTP1B increased K8 Tyr-267 phosphorylation, decreased solubility, and increased K8 filament bundling, whereas PTP1B overexpression had the opposite effects. Furthermore, there was significant co-localization between K8 and a "substrate-trapping" mutant of PTP1B (D181A). Because K8 Tyr-267 is conserved in many IFs (QYE motif), we tested the effect of the paralogous Tyr in glial fibrillary acidic protein (GFAP), which is mutated in Alexander disease (Y242D). Similar to K8, Y242D GFAP exhibited highly irregular filament organization and diminished solubility. Our results implicate the rod domain QYE motif tyrosine as an important determinant of IF assembly and solubility properties that can be dynamically modulated by phosphorylation.

[A case of Alexander disease suspected juvenile-onset and exacerbating after long stationary state]

We report the case of a 40-year-old woman with Alexander disease. She experienced single seizure as 1-year-old, and became less active after that. Her academic records in elementary school were poor. However, she graduated from junior college and was later employed as a clerk for a short duration. Her parents, who lived with her noticed her apathy when she was 38, and gait disturbance soon after. At the age of 40, she was admitted to a hospital because of a fall and was referred to us. Brain magnetic resonance imaging (MRI) showed significant leukodystrophy with frontal predominance, and cervical MRI revealed mild cervical cord atrophy with dilated central canal. We performed genetic analysis and found the R79H variant of the gene encoding the glial fibrillary acidic protein. The patient was diagnosed with Alexander disease and suspedted juvenile-onset on the basis of the genetic analysis and MRI findings. Patients with juvenile Alexander disease have been previously reported to have variable survival, ranging from the early teens to the 20's and 30's. Our patient may suggest that natural history of this disease is more variable than previously thought.

GFAP mutations, age at onset, and clinical subtypes in Alexander disease

OBJECTIVE

To characterize Alexander disease (AxD) phenotypes and determine correlations with age at onset (AAO) and genetic mutation. AxD is an astrogliopathy usually characterized on MRI by leukodystrophy and caused by glial fibrillary acidic protein (GFAP) mutations.

METHODS

We present 30 new cases of AxD and reviewed 185 previously reported cases. We conducted Wilcoxon rank sum tests to identify variables scaling with AAO, survival analysis to identify predictors of mortality, and χ(2) tests to assess the effects of common GFAP mutations. Finally, we performed latent class analysis (LCA) to statistically define AxD subtypes.

RESULTS

LCA identified 2 classes of AxD. Type I is characterized by early onset, seizures, macrocephaly, motor delay, encephalopathy, failure to thrive, paroxysmal deterioration, and typical MRI features. Type II is characterized by later onset, autonomic dysfunction, ocular movement abnormalities, bulbar symptoms, and atypical MRI features. Survival analysis predicted a nearly 2-fold increase in mortality among patients with type I AxD relative to those with type II. R79 and R239 GFAP mutations were most common (16.6% and 20.3% of all cases, respectively). These common mutations predicted distinct clinical outcomes, with R239 predicting the most aggressive course.

CONCLUSIONS

AAO and the GFAP mutation site are important clinical predictors in AxD, with clear correlations to defined patterns of phenotypic expression. We propose revised AxD subtypes, type I and type II, based on analysis of statistically defined patient groups.

The ocular motor features of adult-onset alexander disease: a case and review of the literature

A 51-year-old Chinese man presented with gaze-evoked nystagmus, impaired smooth pursuit and vestibular ocular reflex cancellation, and saccadic dysmetria, along with a family history suggestive of late-onset autosomal dominant parkinsonism. MRI revealed abnormalities of the medulla and cervical spinal cord typical of adult-onset Alexander disease, and genetic testing showed homozygosity for the p.D295N polymorphic allele in the gene encoding the glial fibrillary acidic protein. A review of the literature shows that ocular signs are frequent in adult-onset Alexander disease, most commonly gaze-evoked nystagmus, pendular nystagmus, and/or oculopalatal myoclonus, and less commonly ptosis, miosis, and saccadic dysmetria. These signs are consistent with the propensity of adult-onset Alexander disease to cause medullary abnormalities on neuroimaging.

Neurocognitive decline in Alexander disease

Alexander disease is a neurological condition associated with prominent white matter deterioration. Its rarity and relatively rapid disease course have provided limited understanding into the cognitive effects of the illness. We report the serial neuropsychological findings of a 21-year-old with normal development and no medical history until age 9, when he experienced refractory sinusitis, stabbing headaches with vertigo, disorientation, and decline in academic and social settings. An MRI scan of the brain found acute demyelinating encephalomyelitis, with a preponderance of white matter degeneration in the bilateral frontal lobes. Interval MRIs showed continued degeneration. Confirmation of Alexander disease was made at age 20 through genetic testing. Four evaluations completed from ages 15 to 21 showed impairment across all cognitive domains. Cognitive deficits were most prominent in new learning and recent memory, executive functions, and fine motor dexterity, and less apparent in information processing and visual scanning speed. These results present evidence for a particular cognitive pattern in individuals with juvenile-onset Alexander disease. Despite extensive white matter degeneration in the frontal lobes, certain tasks associated with frontal lobe integrity were relatively preserved. Further research into the neuropsychological presentation of the subtypes of Alexander disease can enhance diagnostic clarity and treatment planning.

Glial fibrillary acidic protein mutations in adult-onset Alexander disease: clinical features observed in 12 Japanese patients

OBJECTIVE

To clarify the clinical manifestations of adult-onset Alexander disease (AOAD) in Japanese patients with glial fibrillary acidic protein (GFAP) gene mutations.

METHODS AND MATERIALS

  Twelve patients of AOAD with GFAP mutations detected in our centre were examined for neurological and magnetic resonance imaging (MRI) findings.

RESULTS

  Major symptoms were pyramidal and bulbar signs. In addition, three patients presented abnormal behaviour and/or memory disturbance. Two of the three patients also had Parkinsonism and had been diagnosed with fronto-temporal dementia or progressive supranuclear palsy until GFAP mutations were detected. Abnormalities of the medulla oblongata and cervical spinal cord were observed on MRI in all patients.

CONCLUSIONS

  Patients presenting with pyramidal and/or bulbar signs with abnormalities of the medulla oblongata and cervical spinal cord on MRI should be considered for GFAP analysis as this is the typical presentation of AOAD. Abnormal behaviour and cognitive disorders including deterioration of memory were rare symptoms but could be an obstacle to diagnosing Alexander disease.

The clinical spectrum of late-onset Alexander disease: a systematic literature review

Following the discovery of glial fibrillary acidic protein (GFAP) mutations as the causative factor of Alexander disease (AxD), new case reports have recently increased, prompting a more detailed comprehension of the clinical features of the three disease subtypes (infantile, juvenile and adult). While the clinical pattern of the infantile form has been substantially confirmed, the late-onset subtypes (i.e., juvenile and adult), once considered rare manifestations of AxD, have displayed a wider clinical spectrum. Our aim was to evaluate the clinical phenotype of the adult and juvenile forms by reviewing the previously reported cases. Data were collected from previously published reports on 112 subjects affected by neuropathologically or genetically proven adult and juvenile Alexander disease. Although the late-onset forms of AxD show a wide clinical variability, a common pattern emerges from comparing previously reported cases, characterized by pseudo-bulbar signs, ataxia, and spasticity, associated with atrophy of the medulla and upper cervical cord on neuroimaging. Late-onset AxD cases can no longer be considered as rare manifestations of the disease. The clinical pattern usually reflects the topographic localization of the lesions, with adult cases displaying a predominant infratentorial localization of the lesions. Juvenile cases show clinical and radiological features which are intermediate between adult and infantile forms.

[Adult onset Alexander disease with a novel variant (S398F) in the glial fibrillary acidic protein gene]

We report a 58-year-old woman with adult onset Alexander disease. At the age of 54 she noticed numbness in bilateral legs and at 57 she developed left sided spastic gait. Her walking difficulty was gradually worsened and followed by the development of weakness in left arm, dysarthria and dysphagia. Her mother and elder brother also had similar clinical presentations which suggested an autosomal dominant neurological disorder. With MRI findings showing localized atrophy of medulla oblongata and upper cervical cord with hyperintensities on T2-weighted image, diagnosis of adult onset Alexander disease was made. We performed genetic analysis and found novel variant (S398F) in the glial fibrillary acidic protein gene. In case of slowly progressive myelopathy with bulbar palsy of unknown origin, especially those with atrophy limited to medulla oblongata and upper cervical cord, adult onset Alexander disease should be taken into consideration.

Neonatal Alexander disease: MR imaging prenatal diagnosis

SUMMARY

Alexander disease (AD) is a rare neurodegenerative disorder characterized by megalencephaly, leukoencephalopathy, and Rosenthal fibers within astrocytes. This report describes the case of a female patient with sonography-detected ventriculomegaly at 32 weeks' gestation and distinctive MR imaging features at 33 and 36 weeks' gestation, at birth, and at 2 months of age, which led to the suggested diagnosis of Alexander disease. Molecular analysis confirmed a missense mutation in the GFAP gene. The literature contains little information on the fetal MR imaging findings that may allow prenatal diagnosis of AD.

Clinical and genetic study in Chinese patients with Alexander disease

Alexander disease is a rare progressive leukoencephalopathy inherited in an autosomal dominant manner. The infantile form is the most common, with onset before 2 years of age. The typical clinical signs include psychomotor retardation and regression, seizures, and megalencephaly. Juvenile and adult forms are also recognized. The neuropathology of Alexander disease is characterized by abundant presence of Rosenthal fibers in astrocytes in the brain. GFAP has been identified to be the only gene associated with Alexander disease since 2001. Only 1 patient with Alexander disease confirmed by genetic testing has been reported in mainland China. To get further information of the clinical and genetic characteristics of Chinese patients, we analyzed an additional 3 cases with the infantile or juvenile form. A novel mutation, Y83H, and a previously reported mutation, R88C, were identified in these patients. Both mutations were heterozygous and de novo. The results of this research expand the number of patients with Alexander disease found to have GFAP coding mutations in mainland China. A novel missense mutation, Y83H, is identified.

Acute onset of fatal vegetative symptoms: unusual presentation of adult Alexander disease

Since genetic analysis of the GFAP gene for the diagnosis of adult Alexander disease (AD) has been established in 2001, several cases of both sporadic and familial cases of AD have been described. Except for one patient, all subjects revealed glial fibrillary acidic protein (GFAP) mutations, and clinical progression of symptoms, mainly bulbar and pseudobulbar, were moderate. Here we report on a patient with acute onset of vegetative symptoms, rapid progression, and death within 2 months. Although histology and final magnetic resonance imaging (MRI) were characteristic of AD, sequencing of the encoding GFAP gene revealed no mutation. We believe that this case report expands the so far known clinical spectrum and MRI dynamics of adult AD, and suggest that analysis of the coding part of GFAP may be inconclusive in rare cases. In such patients, only histology may lead to definitive diagnosis.

GFAP and its role in Alexander disease

Here we review how GFAP mutations cause Alexander disease. The current data suggest that a combination of events cause the disease. These include: (i) the accumulation of GFAP and the formation of characteristic aggregates, called Rosenthal fibers, (ii) the sequestration of the protein chaperones alpha B-crystallin and HSP27 into Rosenthal fibers, and (iii) the activation of both Jnk and the stress response. These then set in motion events that lead to Alexander disease. We discuss parallels with other intermediate filament diseases and assess potential therapies as part of this review as well as emerging trends in disease diagnosis and other aspects concerning GFAP.

The functional alteration of mutant GFAP depends on the location of the domain: morphological and functional studies using astrocytoma-derived cells

To clarify the functional effects of mutant glial fibrillary acidic protein (GFAP), we examined the expression patterns of mutant GFAPs (V87G, R88C, and R416W) in astrocytoma-derived cells and performed migration assay. The morphological change was found in mutant GFAP cells, although the number of changes was small. On migration assay, the migration rate in cells with the V87G or R88C mutation, which are located in the helical rod domain in GFAP, was significantly higher than those of wild-type and R416W. These findings suggest that the functional abnormalities of astrocytes might be induced prior to aggregation of GFAP in Alexander disease and that the functional alteration depends on the location of the domain.

TRH therapy in a patient with juvenile Alexander disease

Alexander disease is a rare disorder of the central nervous system caused by a de novo mutation in the glial fibrillary acidic protein (GFAP) gene. Unlike the much more common infantile form, the juvenile form is slowly progressive with bulbar, pyramidal and cerebellar signs. Herein, we report a 9-year old Japanese girl suffering from frequent vomiting, slurred speech and truncal ataxia. Juvenile Alexander disease was diagnosed by genetic analysis, which detected a novel GFAP mutation, D360V. We also describe our clinical success in treating this patient with thyrotropin releasing hormone (TRH).

An infantile-juvenile form of Alexander disease caused by a R79H mutation in GFAP

Alexander disease is a degenerative white matter disorder due to mutations in the glial fibrillary acidic protein (GFAP) gene. It has been classified into three forms based on the age of onset and severity: an infantile, a juvenile, and an adult form. In a 6-year-old patient with a relatively mild form of Alexander disease, we detected a common R79H mutation in GFAP, previously only described in the infantile form. These results suggest the need for further studies of the genotype-phenotype correlation.

Novel mutation of gene coding for glial fibrillary acidic protein in a Japanese patient with Alexander disease

We report the mutation analysis of a Japanese patient diagnosed with infantile-type Alexander disease. The genetic analysis revealed a new missense mutation, an A to G transition at nucleotide position 1026 in exon 6, leading to the substitution of glycine for glutamic acid at amino acid position 371(E371G). This mutation was not detected in 50 Japanese controls using denaturing high-performance liquid chromatography.

Propensity for paternal inheritance of de novo mutations in Alexander disease

De novo dominant mutations in the GFAP gene have recently been associated with nearly all cases of Alexander disease, a rare but devastating neurological disorder. These heterozygous mutations must occur very early in development and be present in nearly all cells in order to be detected by the sequencing methods used. To investigate whether the mutations may have arisen in the parental germ lines, we determined the parental chromosome bearing the mutations for 28 independent Alexander disease cases. These cases included 17 different missense mutations and one insertion mutation. To enable assignment of the chromosomal origin of the mutations, six new single nucleotide polymorphisms in the GFAP gene were identified, bringing the known total to 26. In 24 of the 28 cases analyzed, the paternal chromosome carried the GFAP mutation (P < 0.001), suggesting that they predominantly arose in the parental germ line, with most occurring during spermatogenesis. No effect of paternal age was observed. There has been considerable debate about the magnitude of the male to female germ line mutation rate; our ratio of 6:1 is consistent with indirect estimates based on the rate of evolution of the sex chromosome relative to the autosomic chromosomes.

Alexander-disease mutation of GFAP causes filament disorganization and decreased solubility of GFAP

Alexander disease is a fatal neurological illness characterized by white-matter degeneration and the formation of astrocytic cytoplasmic inclusions called Rosenthal fibers, which contain the intermediate filament glial fibrillary acidic protein (GFAP), the small heat-shock proteins HSP27 and αB-crystallin, and ubiquitin. Many Alexander-disease patients are heterozygous for one of a set of point mutations in the GFAP gene, all of which result in amino acid substitutions. The biological effects of the most common alteration, R239C, were tested by expressing the mutated protein in cultured cells by transient transfection. In primary rat astrocytes and Cos-7 cells, the mutant GFAP was incorporated into filament networks along with the endogenous GFAP and vimentin, respectively. In SW13Vim– cells, which have no endogenous cytoplasmic intermediate filaments, wild-type human GFAP frequently formed filamentous bundles, whereas the R239C GFAP formed `diffuse' and irregular patterns. Filamentous bundles of R239C GFAP were sometimes formed in SW13Vim– cells when wild-type GFAP was co-transfected. Although the presence of a suitable coassembly partner (vimentin or GFAP) reduced the potential negative effects of the R239C mutation on GFAP network formation, the mutation affected the stability of GFAP in cells in a dominant fashion. Extraction of transfected SW13Vim– cells with Triton-X-100-containing buffers showed that the mutant GFAP was more resistant to solubilization at elevated KCl concentrations. Both wild-type and R239C GFAP assembled into 10 nm filaments with similar morphology in vitro. Thus, although the R239C mutation does not appear to affect filament formation per se, the mutation alters the normal solubility and organization of GFAP networks.