Comorbidities and clinical outcomes in adult- and juvenile-onset Huntington's disease: a study of linked Swedish National Registries (2002-2019)

Comparison of the Clinical Spectrum of Juvenile- and Adult-Onset Huntington Disease: A National Cohort and Enroll-HD Observational Study

BACKGROUND AND OBJECTIVES

Differences in clinical characteristics between juvenile-onset Huntington disease (JHD) and adult-onset HD (AHD) are hypothesized but not directly compared. This study compares clinical characteristics occurrence and severity across age-at-onset (AO) subtypes.

METHODS

Using the national juvenile-onset HD patient cohort and the international Enroll-HD registry (NCT01574053), we compared childhood-onset JHD (cJHD; AO 0-10), adolescent-onset JHD (aJHD; AO 11-20), and adult-onset HD (AHD; AO 21-65) on proportions of clinical characteristics at onset and psychiatric characteristics in pooled datasets. Kruskal-Wallis test was applied to UHDRS-Total Motor Score (UHDRS-TMS) items of the Enroll-HD dataset to compare the severity of motor disease characteristics 6-10 years after onset.

RESULTS

The combined datasets provided data from 46 patients with cJHD (mean AO 6.70, 45% female), 243 patients with aJHD (mean AO 16.70, 46% female), and 9,504 patients with AHD (mean AO 44.70, 51% female). At onset, neurocognitive symptoms occurred in 47.50% of patients with cJHD (n = 46; 95% CI 31.80%-63.70%), significantly more often compared with 24.88% of patients with aJHD (n = 209; 19.30%-31.40%) and 15.02% of those with AHD (n = 8,177; 14.30%-15.80%). Psychiatric symptoms occurred in 47.12% of patients with aJHD (95% CI 40.20%-54.10%), significantly more compared with 31.04% of patients with AHD (30.10%-32.00%). Throughout the disease, aggressive behavior occurred in 73.91% of patients with cJHD (n = 46; 95% CI 58.60%-85.20%) and 55.88% of those with aJHD (n = 238; 49.30%-62.30%), significantly more compared with 40.65% of patients with AHD (n = 9,501; 39.70%-41.70%). Psychosis occurred in 23.53% of patients with aJHD (95% CI 18.40%-29.50%), significantly more compared with 12.77% of those with AHD (12.10%-13.50%). The Kruskal-Wallis test revealed significantly higher median UHDRS-TMS scores in one or both JHD subtypes compared with AHD for dysarthria (AHD: n = 4,163, median 1.00, interquartile range (IQR) 0.70; cJHD: n = 12, 2.20, 2.00, p = 0.039; aJHD: n = 93, 1.00, 1.00, p = 0.031), parkinsonism (AHD: n = 4,158, median 6.00, IQR 4.70; cJHD: n = 12, 11.00, 9.40, p = 0.008; aJHD: n = 93, 8.50, 6.80, p < 0.001), and dystonia (AHD: n = 4,161, median 2.00, IQR 5.20; cJHD: n = 12, 6.50, 8.20, p = 0.141; aJHD: n = 93, 4.00, 7.20, p = 0.015) and significantly lower median scores for chorea (AHD: n = 4,163, median 9.20, IQR 7.00; cJHD: n = 12, 5.00, 4.20, p = <0.001; aJHD: n = 93, 6.30, 9.50, p < 0.001).

DISCUSSION

This study highlights distinct clinical patterns in JHD subtypes compared with AHD. Stratification by age at onset-defined HD subtypes is needed in future studies.

Rare Diseases, Spotlighting Amyotrophic Lateral Sclerosis, Huntington's Disease, and Myasthenia Gravis: Insights from Landscape Analysis of Current Research

Rare diseases are a diverse group of disorders that, despite each individual condition's rarity, collectively affect a significant portion of the global population. Currently approximately 10,000 rare diseases exist globally, with 80% of these diseases being identified as having genetic origins. In this Review, we examine data from the CAS Content Collection to summarize scientific progress in the area of rare diseases. We examine the publication landscape in the area in an effort to provide insights into current advances and developments. We then discuss the evolution of key concepts in the field, genetic associations, as well as the major technologies and development pipelines of rare disease treatments. We focus our attention on three specific rare diseases: (i) amyotrophic lateral sclerosis, a terminal neurodegenerative disease affecting the central nervous system resulting in progressive loss of motor neurons that control voluntary muscles; (ii) Huntington's disease, another terminal neurodegenerative disease that causes progressive degeneration of nerve cells in the brain, with a wide impact on a person's functional abilities; and (iii) myasthenia gravis, a chronic autoimmune synaptopathy leading to skeletal muscle weakness. While the pathogenesis of these rare diseases is being elucidated, there is neither a cure nor preventative treatment available, only symptomatic treatment. The objective of the paper is to provide a broad overview of the evolving landscape of current knowledge on rare diseases and specifically on the biology and genetics of the three spotlighted diseases, to outline challenges and evaluate growth opportunities, an aim to further efforts in solving the remaining challenges.

The microbiota-gut-brain axis in Huntington's disease: pathogenic mechanisms and therapeutic targets

Huntington's disease (HD) is a currently incurable neurogenerative disorder and is typically characterized by progressive movement disorder (including chorea), cognitive deficits (culminating in dementia), psychiatric abnormalities (the most common of which is depression), and peripheral symptoms (including gastrointestinal dysfunction). There are currently no approved disease-modifying therapies available for HD, with death usually occurring approximately 10-25 years after onset, but some therapies hold promising potential. HD subjects are often burdened by chronic diarrhea, constipation, esophageal and gastric inflammation, and a susceptibility to diabetes. Our understanding of the microbiota-gut-brain axis in HD is in its infancy and growing evidence from preclinical and clinical studies suggests a role of gut microbial population imbalance (gut dysbiosis) in HD pathophysiology. The gut and the brain can communicate through the enteric nervous system, immune system, vagus nerve, and microbiota-derived-metabolites including short-chain fatty acids, bile acids, and branched-chain amino acids. This review summarizes supporting evidence demonstrating the alterations in bacterial and fungal composition that may be associated with HD. We focus on mechanisms through which gut dysbiosis may compromise brain and gut health, thus triggering neuroinflammatory responses, and further highlight outcomes of attempts to modulate the gut microbiota as promising therapeutic strategies for HD. Ultimately, we discuss the dearth of data and the need for more longitudinal and translational studies in this nascent field. We suggest future directions to improve our understanding of the association between gut microbes and the pathogenesis of HD, and other 'brain and body disorders'.

Antidopaminergic medications in Huntington's disease

Huntington's disease (HD) is a progressive neurodegenerative disorder marked by motor, cognitive, and behavioral impairments. Antidopaminergic medications (ADMs), such as VMAT2 inhibitors and antipsychotics, are commonly used to manage HD motor disturbances and behavioral disorders. For patients and caregivers, ADMs are an important tool for managing symptoms that negatively affect daily life. However, the impact of ADM use in HD is not firmly understood due to a lack of robust, systematic studies that assessed their overall effect on HD disease. A mounting body of evidence suggests these medications may be associated with worse clinical measures of cognitive function and functional impairment. While regulatory guidelines highlight adverse effects like sedation, cognitive dysfunction, and extrapyramidal symptoms, it is unclear whether ADMs directly impact disease progression or if the side effects mimic or exacerbate measures of HD symptoms in clinical trials. Given ADM effects on the central nervous system and biological uncertainty within HD outcomes, clinical trial designs should recognize the impact of ADMs on key outcomes, as measured by acceptable scales including Total Functional Capacity, Stoop Word Reading, Symbol Digit Modality Test, and the composite Unified Huntington's Disease Rating Scale. The development of novel HD interventions requires consideration of concomitant ADM use that may influence measures of disease presentation. In this review, we highlight the role of ADMs in HD management, their symptomatic benefits and potential risks, especially with high dose associated side effects, interactions with CYP2D6 inhibitors, and the individualized need for careful dose monitoring for clinical care and trial design.

Systemic Symptoms in Huntington's Disease: A Comprehensive Review

BACKGROUND

Although Huntington's disease (HD) is usually thought of as a triad of motor, cognitive, and psychiatric symptoms, there is growing appreciation of HD as a systemic illness affecting the entire body.

OBJECTIVES

This review aims to draw attention to these systemic non-motor symptoms in HD.

METHODS

We identified relevant studies published in English by searching MEDLINE (from 1966 to September 2023), using the following subject headings: Huntington disease, autonomic, systemic, cardiovascular, respiratory, gastrointestinal, urinary, sexual and cutaneous, and additional specific symptoms.

RESULTS

Data from 123 articles were critically reviewed with focus on systemic features associated with HD, such as cardiovascular, respiratory, gastrointestinal, urinary, sexual and sweating.

CONCLUSION

This systematic review draws attention to a variety of systemic and autonomic co-morbidities in patients with HD. Not all of them correlate with the severity of the primary HD symptoms or CAG repeats. More research is needed to better understand the pathophysiology and treatment of systemic and autonomic dysfunction in HD.

Dietary fibre confers therapeutic effects in a preclinical model of Huntington's disease

Huntington's disease (HD) is a neurodegenerative disorder involving psychiatric, cognitive and motor deficits, as well as peripheral symptoms, including gastrointestinal dysfunction. The R6/1 HD mouse model expresses a mutant human huntingtin transgene and has been shown to provide an accurate disease model. Recent evidence of gut microbiome disruption was shown in preclinical and clinical HD. Therefore, we aimed to assess the potential role of gut microbial modulation in the treatment of HD. The R6/1 HD mice and wild-type littermate controls were randomised to receive diets containing different amounts of fibre: high-fibre (10 % fibre), control (5 % fibre), or zero-fibre (0 % fibre), from 6 to 20 weeks of age. We characterized the onset and progression of motor, cognitive and affective deficits, as well as gastrointestinal function and gut morphological changes. Faeces were collected for gut microbiome profiling using 16S rRNA sequencing, at 14 and 20 weeks of age. When compared to the control diet, high-fibre diet improved the performance of HD mice in behavioral tests of cognitive and affective function, as well as the gastrointestinal function of both HD and wild-type mice. While the diets changed the beta diversity of wild-type mice, no statistical significance was observed at 14 or 20 weeks of age within the HD mice. Analysis of Composition of Microbiomes with Bias Correction (ANCOM-BC) models were performed to evaluate microbiota composition, which identified differences, including a decreased relative abundance of the phyla Actinobacteriota, Campylobacterota and Proteobacteria and an increased relative abundance of the families Bacteroidaceae, Oscillospiraceae and Ruminococcaceae in HD mice when compared to wild-type mice after receiving high-fibre diet. PICRUSt2 revealed that high-fibre diet also decreased potentially pathogenic functional pathways in HD. In conclusion, high-fibre intake was effective in enhancing gastrointestinal function, cognition and affective behaviors in HD mice. These findings indicate that dietary fibre interventions may have therapeutic potential in Huntington's disease to delay clinical onset, and have implications for related disorders exhibiting dysfunction of the gut-brain axis.

A Case Series of Delusional Infestation in Huntington's Disease

 Huntington's disease (HD) is an autosomal dominant disorder that affects the basal ganglia, caused by CAG repeats in the huntingtin gene. Delusional infestation (DI) is a rare psychotic manifestation of the disease. This report presents two cases of HD patients with DI, both middle-aged females. The first patient achieved remission of DI with olanzapine, later cross-tapered to risperidone, but had spontaneous relapses. The second experienced gradual resolution of DI with risperidone in the setting of iron repletion and amantadine discontinuation, although her other psychotic symptoms remained. These cases shed light on an uncommon condition and may help guide understanding of the most effective treatment for it.