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Huntington's disease and other choreas
Insights
Chorea, a movement disorder, stems from diverse hereditary and sporadic origins, including Huntington's disease (HD). Identifying the cause is crucial as treatments for chorea symptoms remain limited, though disease-modifying therapies are under investigation.
Area of Science:
- Neurology
- Genetics
- Movement Disorders
Background:
- Chorea is a neurological disorder characterized by involuntary, irregular, and purposeless movements.
- Causes are broadly categorized into hereditary and sporadic types, with Huntington's disease (HD) being a primary hereditary example.
- The clinical presentation of chorea can be complex, sometimes overlapping with other movement disorders or lacking typical features.
Purpose of the Study:
- To review the diverse etiologies of chorea, encompassing both inherited and acquired conditions.
- To highlight the diagnostic challenges, particularly in differentiating conditions like Huntington's disease (HD) and dentatorubro-pallidoluysian atrophy (DRPLA).
- To discuss the current limitations in symptomatic treatment and the emerging landscape of potential disease-modifying therapies.
Main Methods:
- Literature review and synthesis of existing research on chorea.
- Analysis of clinical presentations and genetic underpinnings of hereditary choreiform disorders.
- Compilation of known causes of sporadic chorea, including drug-induced, metabolic, autoimmune, and infectious etiologies.
Main Results:
- Hereditary causes include Huntington's disease (HD) and dentatorubro-pallidoluysian atrophy (DRPLA), both CAG repeat disorders with variable phenotypes.
- Sporadic chorea has numerous causes, such as medications, pregnancy, vascular events, thyrotoxicosis, systemic lupus erythematosus (SLE), and Sydenham's chorea.
- Neuroacanthocytosis is a rare, genetically heterogeneous condition, and "benign hereditary chorea" is exceedingly rare, if it exists.
Conclusions:
- Accurate diagnosis of chorea's underlying cause is essential due to the heterogeneity of conditions and limited symptomatic treatment options.
- While symptomatic management of chorea is often unsatisfactory, research into disease-modifying treatments for conditions like HD is ongoing.
- Understanding the genetic and etiological basis of chorea is critical for developing effective therapeutic strategies.
Abstract:
Chorea can have many causes, some hereditary and many sporadic in nature. The archetypal hereditary cause of chorea is Huntington's disease (HD). However, this condition often manifests as a mixed movement disorder, and some individuals with the Westphal variant may not display chorea at all. Moreover, since gene-specific testing has become available, we now know that in many cases of HD, particularly those with late onset, a positive family history may be lacking. In addition, dentatorubro-pallidoluysian atrophy (DRPLA), another dominantly inherited CAG repeat disease, can produce a similar clinical picture. In both conditions, the phenotype may vary according to repeat length, and anticipation and excess of paternal inheritance in younger-onset cases with longer repeat lengths are seen. Neuroacanthocytosis is probably genetically heterogenous, and many instances of "benign hereditary chorea" have been caused by other conditions. If it exists at all, this disorder is exceedingly rare. The principal causes of sporadic chorea include drugs, pregnancy, vascular disease, thyrotoxicosis, systemic lupus erythematosus (SLE) and the lupus anticoagulant syndrome, polycythaemia rubra vera, AIDS and both initial and recurrent Sydenham's chorea. The symptomatic treatment of chorea is unsatisfactory and, at least in HD, neuropsychiatric disturbance may be much more important for the family. Potential disease-modifying treatments such as anti-excitotoxins, antioxidants, free radical scavengers and neuronal grafting are now being explored in this condition.