Case Report: HSV-2 Encephalitis Presenting With Chorea; Effects of Infection Alone or Combination of Infection and Autoimmunity?

Autoimmune-related movement disorders

Movement disorders (MDs) are common symptoms of autoimmune diseases. However, the clinical spectrum of MDs in autoimmune diseases remains poorly characterized, largely due to the scarcity of large-scale clinical surveys and trials. Most available data are derived from case reports and small case series. Here, we review the 123 currently reported cases of patients with autoimmune-related MDs and evaluate the demographic and clinical characteristics, pathophysiologies, and treatments. Autoimmune MDs were observed in various diseases involving autoimmune processes, including autoimmune encephalitis (AE), central nervous system infections, and systemic autoimmune diseases; even some typical autoimmune diseases of the peripheral nervous system may also cause MDs. Owing to the diversity of aetiologies and pathophysiologies of these diseases, the clinical characteristics and prognoses of these autoimmune-related MDs are highly variable. The mechanisms underlying MDs in autoimmune diseases involve abnormalities in neuronal signalling pathways, including neurotransmitter and receptor dysfunction, as well as direct antibody-mediated attacks on neuronal structures.

Recent advances in non-Huntington's disease choreas

INTRODUCTION

Chorea is primarily due to an imbalance of basal ganglia output pathways, often due to dysfunction or degeneration of the caudate nucleus and putamen, and can be due to many causes.

METHODS

We reviewed the recent literature to identify newly-recognized causes of chorea, including auto-immune, metabolic, and genetic. We also focused upon developments in mechanisms relating to underlying pathophysiology of certain genetic choreas and advances in therapeutics.

RESULTS

Novel autoantibodies continue to be identified as causes of chorea. Both COVID-19 infection and vaccination are reported to result rarely in chorea, although in some cases causality is not clearly established. Advances in genetic testing continue to find more causes of chorea, and to expand the phenotype of known genetic disorders. Deep brain stimulation can be successful in certain circumstances.

CONCLUSION

Our understanding of mechanisms underlying this movement disorder continues to advance, however much remains to be elucidated.

Diagnostic Uncertainties: Chorea

Chorea is a hyperkinetic movement disorder with a multitude of potential etiologies, both acquired and inherited. Although the differential diagnosis for new-onset chorea is extensive, there are often clues in the history, exam, and basic testing that can help to narrow the options. Evaluation for treatable or reversible causes should take priority, as rapid diagnosis can lead to more favorable outcomes. While Huntington's disease is most common genetic cause of chorea, multiple phenocopies also exist and should be considered if Huntington gene testing is negative. The decision of what additional genetic testing to pursue should be based on both clinical and epidemiological factors. The following review provides an overview of the many possible etiologies as well as a practical approach for a patient presenting with new-onset chorea.

Chorea in the Elderly: A Differential Diagnosis and Case Report of Late-Onset Huntington's Disease in an Octogenarian

The term "senile chorea" was previously used to describe cases of insidious onset chorea in elderly patients who lacked family history of chorea. However, many of these patients have an identifiable etiology for their chorea. In this article, we discuss a case of generalized, insidious onset chorea in an 89-year-old man and apply a systematic diagnostic approach to chorea in the elderly to arrive at a diagnosis of late-onset Huntington's disease. He is to our knowledge the second oldest case of late-onset Huntington's disease reported in the literature and his case lends support to the expanding phenotype of Huntington's disease.