Characteristics of cerebral lesions in adult-onset Alexander disease

Genetics behind Cerebral Disease with Ocular Comorbidity: Finding Parallels between the Brain and Eye Molecular Pathology

Cerebral visual impairments (CVIs) is an umbrella term that categorizes miscellaneous visual defects with parallel genetic brain disorders. While the manifestations of CVIs are diverse and ambiguous, molecular diagnostics stand out as a powerful approach for understanding pathomechanisms in CVIs. Nevertheless, the characterization of CVI disease cohorts has been fragmented and lacks integration. By revisiting the genome-wide and phenome-wide association studies (GWAS and PheWAS), we clustered a handful of renowned CVIs into five ontology groups, namely ciliopathies (Joubert syndrome, Bardet–Biedl syndrome, Alstrom syndrome), demyelination diseases (multiple sclerosis, Alexander disease, Pelizaeus–Merzbacher disease), transcriptional deregulation diseases (Mowat–Wilson disease, Pitt–Hopkins disease, Rett syndrome, Cockayne syndrome, X-linked alpha-thalassaemia mental retardation), compromised peroxisome disorders (Zellweger spectrum disorder, Refsum disease), and channelopathies (neuromyelitis optica spectrum disorder), and reviewed several mutation hotspots currently found to be associated with the CVIs. Moreover, we discussed the common manifestations in the brain and the eye, and collated animal study findings to discuss plausible gene editing strategies for future CVI correction.

Clinical and radiological characteristics of older-adult-onset Alexander disease

BACKGROUND

Alexander disease (ALXDRD) affects a wide range of ages from infancy to adulthood. However, only a few cases involving patients with older-adult onset over 65 years of age have been reported. In contrast, regarding in-house data, 10.6% of 85 cases with the identification of GFAP mutations demonstrated older-adult onset. This discrepancy may be due to poor awareness of such cases.

METHODS

The subjects included 9 older-adult-onset cases, with an onset age of 65 years or older. We characterized older-adult-onset ALXDRD by assessing neurological findings and several magnetic resonance imaging (MRI) parameters.

RESULTS

The age at onset, mean age at diagnosis, and mean period from onset to diagnosis were 68.2 years, 70.4 years, and 2.2 years, respectively. The main neurological features at diagnosis included pyramidal signs with muscle weakness and/or cerebellar ataxia. Two-thirds of cases were dependent, and the dependence was significantly correlated with a longer period from onset to diagnosis. Quantitative MRI evaluation for brainstem atrophy demonstrated distinctive morphological features of bulbospinal ALXDRD. The corpus callosum index tended to be negatively correlated with the period from onset to diagnosis.

CONCLUSIONS

Although neurological and MRI findings of older-adult-onset ALXDRD patients showed typical features of bulbospinal ALXDRD, their disease progression was more severe than that in younger-adult-onset ALXDRD, and patients developed dependence within 2 years from onset. Cerebral white matter damage tended to progress in proportion to the duration of illness. Our case study may help to advance understanding of the clinical spectrum of ALXDRD.

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.