A novel adult case of juvenile-onset Alexander disease: complete remission of neurological symptoms for over 12 years, despite insidiously progressive cervicomedullary atrophy

Whole exome/genome sequencing in cyclic vomiting syndrome reveals multiple candidate genes, suggesting a model of elevated intracellular cations and mitochondrial dysfunction

Objective

To utilize whole exome or genome sequencing and the scientific literature for identifying candidate genes for cyclic vomiting syndrome (CVS), an idiopathic migraine variant with paroxysmal nausea and vomiting.

Methods

A retrospective chart review of 80 unrelated participants, ascertained by a quaternary care CVS specialist, was conducted. Genes associated with paroxysmal symptoms were identified querying the literature for genes associated with dominant cases of intermittent vomiting or both discomfort and disability; among which the raw genetic sequence was reviewed. "Qualifying" variants were defined as coding, rare, and conserved. Additionally, "Key Qualifying" variants were Pathogenic/Likely Pathogenic, or "Clinical" based upon the presence of a corresponding diagnosis. Candidate association to CVS was based on a point system.

Results

Thirty-five paroxysmal genes were identified per the literature review. Among these, 12 genes were scored as "Highly likely" (SCN4A, CACNA1A, CACNA1S, RYR2, TRAP1, MEFV) or "Likely" (SCN9A, TNFRSF1A, POLG, SCN10A, POGZ, TRPA1) CVS related. Nine additional genes (OTC, ATP1A3, ATP1A2, GFAP, SLC2A1, TUBB3, PPM1D, CHAMP1, HMBS) had sufficient evidence in the literature but not from our study participants. Candidate status for mitochondrial DNA was confirmed by the literature and our study data. Among the above-listed 22 CVS candidate genes, a Key Qualifying variant was identified in 31/80 (34%), and any Qualifying variant was present in 61/80 (76%) of participants. These findings were highly statistically significant (p < 0.0001, p = 0.004, respectively) compared to an alternative hypothesis/control group regarding brain neurotransmitter receptor genes. Additional, post-analyses, less-intensive review of all genes (exome) outside our paroxysmal genes identified 13 additional genes as "Possibly" CVS related.

Conclusion

All 22 CVS candidate genes are associated with either cation transport or energy metabolism (14 directly, 8 indirectly). Our findings suggest a cellular model in which aberrant ion gradients lead to mitochondrial dysfunction, or vice versa, in a pathogenic vicious cycle of cellular hyperexcitability. Among the non-paroxysmal genes identified, 5 are known causes of peripheral neuropathy. Our model is consistent with multiple current hypotheses of CVS.

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.

Clinical characteristics of Alexander disease

Alexander disease (ALXDRD) is a primary astrocyte disease caused by GFAP gene mutation. The clinical features of ALXDRD vary from infantile-onset cerebral white matter involvement to adult-onset brainstem involvement. Several studies revealed that the level of GFAP overexpression is correlated with disease severity, and basic research on therapies to reduce abnormal GFAP accumulation has recently been published. Therefore, the accumulation of clinical data to advance understanding of the natural history is essential for clinical trials expected in the future. This review focuses on the clinical characteristics of ALXDRD including the clinical symptoms, imaging findings and genetics to provide diagnostic information useful in daily clinical practice.

[Clinical characteristics and diagnostic criteria on Alexander disease]

Alexander disease (ALXDRD) is a primary astrocyte disease caused by glial fibrillary acidic protein (GFAP) gene mutation. ALXDRD had been clinically regarded as a cerebral white matter disease that affects only children for about 50 years since the initial report in 1949; however, in the early part of the 21st century, case reports of adult-onset ALXDRD with medulla and spinal cord lesions increased. Basic research on therapies to reduce abnormal GFAP accumulation, such as drug-repositioning and antisense oligonucleotide suppression, has recently been published. The accumulation of clinical data to advance understanding of natural history is essential for clinical trials expected in the future. In this review, I classified ALXDRD into two subtypes: early-onset and late-onset, and detail the clinical symptoms, imaging findings, and genetic characteristics as well as the epidemiology and historical changes in the clinical classification described in the literature. The diagnostic criteria based on Japanese ALXDRD patients that are useful in daily clinical practice are also mentioned.

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.

Alexander's disease and the story of Louise

We describe the rare condition known as Alexander's disease or Alexander's leukodystrophy, which is essentially a childhood dementia. We then present the case of Louise Davies (we are using Louise's real name with the permission and special request of her mother), a woman who was diagnosed with this disease at the age of 5 years and is still alive at the age of 38, making her the longest known survivor of this condition. Although now severely impaired, both physically and mentally, and able to do very little, she has lived far longer than expected. We present some neuropsychological results from her childhood before measuring her decline over the past four years. We conclude by considering whether or not the diagnosis was correct and why she has lived so long.

[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.

Familial adult-onset Alexander disease with a novel mutation (D78N) in the glial fibrillary acidic protein gene with unusual bilateral basal ganglia involvement

In this report, we describe the case of a new Japanese family (32 to 64 years old; 2 females and 1 male) affected by adult-onset Alexander disease. Clinically, one member (age at onset, 56 years old) developed cerebellar ataxia, another (age at onset, 55 years old) showed cerebellar ataxia and pseudobulbar signs, and one member (32 years old) was asymptomatic. Marked atrophy of the medulla oblongata and spinal cord was detected in the two symptomatic patients by magnetic resonance imaging (MRI). However, in the asymptomatic patient, cervicomedullary atrophy was mild. Hyperintensity signals in the medulla oblongata were detected in the two symptomatic patients, but not in the asymptomatic patient. In addition, there are symmetrical hyperintensity signals in the posterior part of the globus pallidus on T2-weighted images in the two symptomatic patients, which are rarely observed in adult-onset Alexander disease. Molecular genetic analysis revealed a novel missense mutation (p. D78N) in the glial fibrillary acidic protein (GFAP) gene in this family. The typical atrophy of the medulla oblongata and upper cervical cord detected by MRI is the diagnostic feature of adult-onset Alexander disease. Genetic analysis of the GFAP gene is recommended for all patients with late-onset progressive ataxia and suspected of having adult-onset Alexander disease on the basis of MRI findings. Additionally, these characteristic MRI patterns might even lead to the identification of asymptomatic cases, as in one of our cases.