Case report of optic atrophy in Dentatorubropallidoluysian Atrophy (DRPLA)

Dentatorubral-pallidoluysian atrophy: a rare cause of epilepsy, ataxia and chorea

A 34-year-old woman presented with insidious onset and gradually progressive cerebellar ataxia over 10 years, with generalised convulsions. On examination, there were myoclonic jerks, choreiform movements and cerebellar syndrome. Her family history suggested an autosomal dominant inheritance with anticipation. Genetic analysis for trinucleotide repeat disorders led to a diagnosis of dentatorubral-pallidoluysian atrophy (60 CAG repeats in the atrophin-1 gene). This rare spinocerebellar ataxia should be considered in the differential diagnosis of inherited ataxia when combined with seizures and chorea. Other features suggesting a repeat expansion disorder are variable phenotypes within the same family and possible anticipation.

A Review of Ocular Movement Abnormalities in Hereditary Cerebellar Ataxias

Cerebellar ataxias are a wide heterogeneous group of disorders that may present with fine motor deficits as well as gait and balance disturbances that have a significant influence on everyday activities. To review the ocular movements in cerebellar ataxias in order to improve the clinical knowledge of cerebellar ataxias and related subtypes. English papers published from January 1990 to May 2022 were selected by searching PubMed services. The main search keywords were ocular motor, oculomotor, eye movement, eye motility, and ocular motility, along with each ataxia subtype. The eligible papers were analyzed for clinical presentation, involved mutations, the underlying pathology, and ocular movement alterations. Forty-three subtypes of spinocerebellar ataxias and a number of autosomal dominant and autosomal recessive ataxias were discussed in terms of pathology, clinical manifestations, involved mutations, and with a focus on the ocular abnormalities. A flowchart has been made using ocular movement manifestations to differentiate different ataxia subtypes. And underlying pathology of each subtype is reviewed in form of illustrated models to reach a better understanding of each disorder.

Case report: Corneal endothelial degeneration and optic atrophy in dentatorubral-pallidoluysian atrophy quantified by specular micrography and optical coherence tomography

Introduction

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disease with various neurological manifestations. Corneal endothelial degeneration and optic atrophy have been reported separately; however, there are no reports of corneal endothelial degeneration with optic atrophy.

Cases

Herein, we present four related patients with DRPLA: two patients (69-year-old woman and 80-year-old man) who exhibited both corneal endothelial degeneration and optic atrophy and another two (49- and 51-year-old women, respectively) who exhibited only corneal endothelial degeneration. We quantified the reduction in corneal endothelial cell density (ECD) and hexagonality using specular microscopy and thinning of the circumpapillary retinal nerve fiber layer (RNFL) using optical coherence tomography (OCT).

Conclusion

This is the first report of DRPLA accompanied by corneal endothelial degeneration and/or optic atrophy, which were both quantified based on the corneal ECD and the circumpapillary RNFL thickness using specular micrography and OCT, respectively. The pathophysiological mechanism is unclear; however, the involvement of the nuclear receptor TLX interacting with atrophin-1 may be implicated in ophthalmic manifestations of DRPLA. Therefore, we recommend performing specular micrography and/or OCT when patients with DRPLA experience visual disturbances.

DRPLA: understanding the natural history and developing biomarkers to accelerate therapeutic trials in a globally rare repeat expansion disorder

Dentatorubral–pallidoluysian atrophy (DRPLA) is a rare neurodegenerative disorder caused by CAG repeat expansions in the atrophin-1 gene and is inherited in an autosomal dominant fashion. There are currently no disease-modifying treatments available. The broad development of therapies for DRPLA, as well as other similar rare diseases, has hit a roadblock due to the rarity of the condition and the wide global distribution of patients and families, consequently inhibiting biomarker development and therapeutic research. Considering the shifting focus towards diverse populations, widespread genetic testing, rapid advancements in the development of clinical and wet biomarkers for Huntington’s disease (HD), and the ongoing clinical trials for antisense oligonucleotide (ASO) therapies, the prospect of developing effective treatments in rare disorders has completely changed. The awareness of the HD ASO program has prompted global collaboration for rare disorders in natural history studies and the development of biomarkers, with the eventual goal of undergoing treatment trials. Here, we discuss DRPLA, which shares similarities with HD, and how in this and other repeat expansion disorders, neurogenetics groups like ours at UCL are gearing up for forthcoming natural history studies to accelerate future ASO treatment trials to hopefully emulate the progress seen in HD.

Dentatorubral-pallidoluysian Atrophy: An Update

Background

Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare, autosomal dominantly inherited disorder characterized by myoclonus, epilepsy, ataxia, and dementia. Diagnosis is challenging due to the heterogeneous presentation and symptomatic overlap with other spinocerebellar ataxias. Symptoms vary according to age of onset, with a mean age at onset of 31 years. A CAG repeat expansion in the ATN1 gene results in neuronal intranuclear inclusions, variable neuronal loss, and astrocytosis in the globus pallidus, dentate and red nuclei. No disease-modifying or curative treatments are currently available

Methods

We performed an online literature search using PubMed for all articles published in an English Language format on the topics of DRPLA or ATN1 over the last 10 years. Where these articles cited other research as support for findings, or statements, these articles were also reviewed. Contemporary articles from related research fields (e.g., Huntington’s Disease) were also included to support statements.

Results

Forty-seven articles were identified, 10 were unobtainable and 10 provided no relevant information. The remaining 27 articles were then used for the review template: seven case reports, seven case series, six model system articles (one review article), four population clinical and genetic studies (one review article), two general review articles, and one human gene expression study. Other cited articles or research from related fields gave a further 42 articles, producing a total of 69 articles cited: 15 case series (including eight family studies), 14 model systems (one review article), 14 population clinical and genetic studies (two review articles), 10 case reports, eight clinical trials/guidelines, four genetic methodology articles, three general review articles, and one human gene expression study.

Discussion

DRPLA remains an intractable, progressive, neurodegenerative disorder without effective treatment. Early recognition of the disorder may improve patient understanding, and access to services and treatments. Large-scale studies are lacking, but are required to characterize the full allelic architecture of the disorder in all populations and the heterogeneous phenotypic spectrum, including neuroimaging findings, possible biomarkers, and responses to treatment.