Infantile Alexander disease: a GFAP mutation in monozygotic twins and novel mutations in two other patients

Type I Alexander disease: Update and validation of the clinical evolution-based classification

BACKGROUND AND OBJECTIVES

Alexander disease (AxD) is a rare progressive leukodystrophy caused by autosomal dominant mutations in the Glial Fibrillary Acidic Protein (GFAP) gene. Three main disease classifications are currently in use, the traditional one defined by the age of onset, and two other based on clinical features at onset and brain MRI findings. Recently, we proposed a new classification, which is based on taking into consideration not only the presenting features, but also data related to the clinical course. In this study, we tried to apply this modified classification system to the cases of pediatric-onset AxD described in literature.

METHODS

A literature review was conducted in PubMed for articles published between 1949 to date. Articles that reported no patient's medical history and the articles about Adult-onset AxD were excluded. We included patients with a confirmed diagnosis of pediatric-onset AxD and of whom information about age and symptoms at onset, developmental milestones and loss of motor and language skills was available.

RESULTS

Clinical data from 205 patients affected with pediatric-onset AxD were retrospectively reviewed. Among these, we identified 65 patients, of whom we had enough information about the clinical course and developmental milestones, and we assessed their disease evolutionary trajectories over time.

DISCUSSION

Our results confirm that patients with Type I AxD might be classified into four subgroups (Ia, Ib, Ic, Id) basing on follow up data. In fact, despite the great variability of phenotypes in AxD, there are some shared trajectories of the disease evolution over time.

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.

Severe worsening of adult-onset Alexander disease after minor head trauma: Report of two patients and review of the literature

Alexander disease (ALXDRD) is a rare astrocytic leukodystrophy caused by GFAP mutations. The adult-onset (AO) variant is usually characterized by gradual onset of spastic ataxia and bulbar symptoms with slowly progressive course. We report two AO-ALXDRD cases with rapid worsening after minor head trauma. In one of them, the only post-traumatic neuroimaging change was revealed by diffusion tensor imaging study. Our observations support the link between head trauma and ALXDRD progression, and suggest that this progression may be ascribed to microstructural changes. Clinicians should inform ALXDRD patients to minimize the risk of head trauma.

Alexander disease

Alexander disease is a rare and generally fatal disorder of the central nervous system, originally defined by the distinctive neuropathology consisting of abundant Rosenthal fibers within the cytoplasm and processes of astrocytes. More recently, mutations in GFAP, encoding glial fibrillary acidic protein, the major intermediate filament protein of astrocytes, have been identified in nearly all patients. No other genetic causes have yet been identified. The precise mechanisms by which mutations lead to disease are poorly understood. Despite the genetic homogeneity, there are a wide range of clinical phenotypes. The genetic issues and the approach to diagnosis are the prime consideration in this chapter.

[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.

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.

Serial MRI changes in a patient with infantile Alexander disease and prolonged survival

Alexander disease is a major entity of leukodystrophy; magnetic resonance imaging (MRI) studies of the brain typically show extensive changes in the cerebral white matter with frontal predominance. Heterozygous missense mutations of GFAP are thought to be sufficient for the molecular diagnosis, which has widened the Alexander disease entity beyond the classical one. We report the patient, a 16-year-old Japanese boy, with infantile-onset Alexander disease, showing striking MRI findings; extreme white matter loss of cerebrum through cerebellum, severe atrophy of basal ganglia, cerebellum, brain stem, and cervical spinal cord. Molecular analysis showed a heterozygous mutation R239L (c.730G>T) in GFAP. A relative long disease course, over 15years, with the help of mechanical ventilation revealed the striking MRI progression.

De novo RYR1 heterozygous mutation (I4898T) causing lethal core-rod myopathy in twins

"Core-rod myopathy" is a rare congenital myopathy characterized by the presence of "cores" and "rods" in distinct locations in the same or different muscle fibres. This association is linked currently to mutations in RYR1, NEB and ACTA1 genes. We report identical twins who presented with polyhydramnios and loss of fetal motility during pregnancy; hypotonia, arthrogryposis and swallowing impairment at birth; need of immediate respiratory support and death at 27 and 50 days of life. Muscle biopsies, performed at 27 days of life in twin 1 and at 49 days in twin 2, showed the presence of separate cores and rods in the muscle fibres, both at light and electron microscopy. The molecular analysis showed a heterozygous de novo mutation (Ile4898Thr) of the RYR1 gene. The molecular study of ACTA1, TMP2 and TMP3 genes did not show abnormalities. This is the first report of a lethal form of congenital "core-rod myopathy". The mutation Ile4898Thr has been previously described in central core disease but not in core-rod myopathy. The report enlarges the phenotypic spectrum of "core-rod myopathy" and highlights the morphological variability associated to special RYR1 mutations.

GFAP mutations and polymorphisms in 13 unrelated Italian patients affected by Alexander disease

Alexander disease (AD), a rare neurodegenerative disorder of the central nervous system, is characterized by the accumulation of cytoplasmic protein aggregates (Rosenthal fibers) composed of glial fibrillary acidic protein (GFAP) and small heat-shock proteins within astrocytes. To date, more than 40 different GFAP mutations have been reported in AD. The present study is aimed at the molecular diagnosis of Italian patients suspected to be affected by AD. By analyzing the GFAP gene of 13 unrelated patients (eight with infantile form, two with juvenile form and three with adult form), we found 11 different alleles, including four new ones. Among the novel mutations, three (p.R70Q, p.R73K, and p.R79P) were identified in exon 1 and p.L359P in exon 6. The sequence analysis also detected six different single nucleotide polymorphic variants, including two previously unreported ones, spread throughout non-coding regions (introns 2, 3, 5, 6, and 3'UTR) of the gene. All patients were heterozygous for the mutations, thus confirming their dominant effect.

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.

Early mitochondrial dysfunction in an infant with Alexander disease

Alexander disease is a neurodegenerative disorder characterized by macrocephaly and progressive demyelination with frontal lobe preponderance. The infantile form, the most frequent variant, appears between birth and 2 years of age and involves a severe course with a rapid neurologic deterioration. Although magnetic resonance imaging is useful for diagnosis, currently diagnosis is confirmed by the finding of missense mutation in the glial fibrillary acidic protein (GFAP) gene. This case reports a female who presented at the age of 5 months with refractory epilepsy and hypotonia. Laboratory examinations, muscle biopsy examination, and energetic metabolic study in muscle indicated increased concentrations of lactate, mitochondria with structural abnormalities, and decreased cytochrome-c oxidase activity respectively. Later, both clinical course and magnetic resonance findings were compatible with Alexander disease, which was confirmed by the finding of a novel glial fibrillary acidic protein gene mutation.

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.

Unusual variants of Alexander's disease

The purpose of this study was to describe unusual variants of Alexander's disease. We studied 10 patients who did not meet previously established magnetic resonance imaging (MRI) criteria for Alexander's disease, but for whom this diagnosis was considered because of Rosenthal fibers at histological examination or presence of some MRI features suggestive of Alexander's disease. Sequence analysis of the GFAP gene was performed. In eight patients, MRI results showed predominantly posterior fossa lesions, especially multiple tumor-like brainstem lesions. One patient had asymmetrical frontal white matter abnormalities and basal ganglia abnormalities. One patient (Patient 10) developed degeneration of the frontal white matter. In nine patients, a mutation was found that was concluded to be pathogenic, because the mutation was de novo (five patients), a known mutation was found (two patients), or assembly of the glial fibrillary acidic protein was abnormal in cultured cells (two patients). In Patient 10, a DNA variation was found that was also present in the patient's clinically unaffected father and was concluded to be a polymorphism. In conclusion, DNA diagnostics is warranted in patients who display MRI features suggestive of Alexander's disease, even if they do not meet the full set of previously established MRI criteria.

Glial fibrillary acidic protein mutations in infantile, juvenile, and adult forms of Alexander disease

Alexander disease is a progressive, usually fatal neurological disorder defined by the widespread and abundant presence in astrocytes of protein aggregates called Rosenthal fibers. The disease most often occurs in infants younger than 2 years and has been labeled a leukodystrophy because of an accompanying severe myelin deficit in the frontal lobes. Later onset forms have also been recognized based on the presence of abundant Rosenthal fibers. In these cases, clinical signs and pathology can be quite different from the infantile form, raising the question whether they share the same underlying cause. Recently, we and others have found pathogenic, de novo missense mutations in the glial fibrillary acidic protein gene in most infantile patients examined and in a few later onset patients. To obtain further information about the role of glial fibrillary acidic protein mutations in Alexander disease, we analyzed 41 new patients and another 3 previously described clinically, including 18 later onset patients. Our results show that dominant missense glial fibrillary acidic protein mutations account for nearly all forms of this disorder. They also significantly expand the catalog of responsible mutations, verify the value of magnetic resonance imaging diagnosis, indicate an unexpected male predominance for the juvenile form, and provide insights into phenotype-genotype relations.

Alexander disease: a leukodystrophy caused by a mutation in GFAP

Alexander disease, a rare fatal disorder of the central nervous system, causes progressive loss of motor and mental function. Until recently it was of unknown etiology, almost all cases were sporadic, and there was no effective treatment. It was most common in an infantile form, somewhat less so in a juvenile form, and was rarely seen in an adult-onset form. A number of investigators have now shown that almost all cases of Alexander disease have a dominant mutation in one allele of the gene for glial fibrillary acidic protein (GFAP) that causes replacement of one amino acid for another. Only in very rare cases of the adult-onset form is the mutation present in either parent. Thus, in almost all cases, the mutation arises as a spontaneous event, possibly in the germ cell of one parent.

A novel GFAP mutation and disseminated white matter lesions: adult Alexander disease?

The recent discovery of heterozygous de novo mutations in the glial fibrillary acidic protein (GFAP) gene as the cause of infantile and juvenile Alexander disease has shed new light on the long-standing debate whether the adult subtype has the same etiology as infantile and juvenile Alexander disease. A 40-year-old man presented with subacute left hemiplegia and ataxia. Cranial MRI revealed disseminated patchy white matter changes involving the corpus callosum, basal ganglia and brainstem. CSF investigation demonstrated elevated total protein but was otherwise normal. Mutation analysis of the GFAP gene was performed in the patient, his mother and healthy brother. A novel heterozygous mutation in exon 4, 681G-->C, predicting an amino acid substitution E223Q in the rod region of GFAP was detected in the patient and his mother but not in his healthy brother or 150 control chromosomes. We conclude that the patient is actually afflicted with Alexander disease. Mutation analysis of GFAP should be considered in patients with remitting neurological deficits, disseminated white matter lesions and absence of inflammatory CSF changes.

A case of adult-onset Alexander disease with Arg416Trp human glial fibrillary acidic protein gene mutation

Heterozygous point mutations in the coding region of the human glial fibrillary acidic protein (GFAP) gene have been reported in patients with various forms of Alexander disease (AD). We report a case of genetically confirmed adult-onset AD with palatal myoclonus, pyramidal tract signs, cerebellar signs, and marked atrophy of the medulla oblongata and spinal cord, autonomic dysfunction and heterozygous R416W GFAP mutation. Interestingly, this R416W mutation has also been reported in both infantile and juvenile forms of Alexander disease. The fact that a R416W mutation causes various types of AD suggests that clinical severities of AD are due not only to the different sites and nature of mutations in GFAP, but also to other modifying factor(s).

Alexander's disease: clinical, pathologic, and genetic features

Alexander's disease, a rare and fatal disorder of the central nervous system, most commonly affects infants and young children but can also occur in older children and sometimes adults. In infants and young children, it causes developmental delay, psychomotor retardation, paraparesis, feeding problems, usually megalencephaly, often seizures, and sometimes hydrocephalus. Juvenile cases often do not have megalencephaly and tend to have predominant pseudobulbar and bulbar signs. In both groups, characteristic magnetic resonance imaging findings have been described. In adult cases, the signs are variable, can resemble multiple sclerosis, and might include palatal myoclonus. In all cases, the examination of brain tissue shows the presence of widely distributed Rosenthal fibers. Almost all cases have recently been found to have a heterozygous, missense, point mutation in the gene for glial fibrillary acidic protein, which provides a new diagnostic tool. In most cases, the mutation appears to occur de novo, not being present in either parent, but some adult cases are familial.

Structural and functional characterization of the zebrafish gene for glial fibrillary acidic protein, GFAP

Glial fibrillary acidic protein, GFAP, is an astrocyte-specific member of the family of intermediate filament proteins which are involved in formation of the cytoskeletal structure. We here present a characterization of the zebrafish GFAP gene and corresponding protein. The zebrafish GFAP gene have the same exon-intron organization as the mammalian orthologoue genes. Comparison of the protein with mammalian GFAP shows that the amino acid sequence is highly conserved in the rod and tail domains whereas the head domain has diverged. Zebrafish GFAP exhibits functional characteristics of an intermediate filament protein such as dimerization potential, capacity to assembly into filaments, and cytoskeletal localization. Mutations in human GFAP have been associated with a severe childhood brain disorder called Alexander disease. Interestingly, the mutations affect preferentially amino acid residues of GFAP that are evolutionarily conserved. This indicates that a change of functionally core residues in GFAP is a prerequisite for the disease phenotype to develop and the initial steps in the pathogenesis may thus be modeled in zebrafish.

Alexander disease

Alexander disease is a rare disorder with limited understanding of its cause, although it does seem to be a disorder of astrocytes rather than a leukodystrophy. It can be divided into three groups: infantile, juvenile, and adult. The infantile type shows enlargement of the head, retarded development and evidence of a severe neurological disorder. The juvenile sufferers are more likely to exhibit bulbar signs, and may not be significantly retarded. Among adults the condition can fluctuate, and so mimic multiple sclerosis. The differential diagnosis in these three groups is discussed, especially the unusual ways in which they can present. The definitive diagnosis may depend on demonstrating Rosenthal fibres in a brain biopsy, or at autopsy, but other tests can be suggestive. The cerebrospinal fluid can show an elevation of B-crystallin and heat shock protein, and the GFAP gene is considered a reliable marker. The EEG and magnetic imaging findings are non-specific. Pathological studies of the brain can be characteristic with demyelination, especially in the frontal lobes, and Rosenthal fibres concentrated in the subpial and subependymal areas. It is possible that these fibres cause a dysfunction of the astrocytes. The genetic investigations are reviewed, and possible causes are discussed. These remain theoretical, but it has been suggested that the disorder is a response to stress from some unknown stimulus. Rosenthal fibres seem to be the result of the condition, although they may be related to the aetiology. There is no specific treatment.