Huntington's Disease

Huntington's disease is a genetically autosomal-dominant inherited neurodegenerative disease (Perandones, Radrizzani, and Micheli, 2010). Its phenotype encompasses chorea, coordination difficulties, cognitive deficits as well as behavioral problems. The genetic defect is caused by a CAG repeat expansion for coding of the HD gene huntingtin (htt). Huntington's disease is a disease that becomes apparent around the age of fourty years, but the disease can in sporadic cases also emerge in a wider age range (e.g. early onset). Huntington's disease is also known for personality changes in the patients, such as anger outburst. The most important neuropathology is associated with dysfunction in the basal ganglia.

Clinical correlates of huntington's disease include as mentioned earlier chorea. In the greek language chorea means "dance". Choreatic movements of the afflicted patient are involuntary and slow and presents it at random. The muscles that are associated with this symptom are all voluntary muscle groups.

In the early course of huntington's disease these choreatic movements may be mild, however with the progression of the disease these movements interfere with daily activities (Perandones et al., 2010). At the end stage of the disease these movements might diminish and are replaced by rigidity and dystonia. Other movement impairments found in huntington's disease are bradykinesia.

Huntington's disease is also associated with cognitive impairments, including executive function deficits, impairments in short-term and visuospatial skills (Perandones et al., 2010). First, these impairments are rather mild, however as the disease advances more global subcortical dementia may emerge. The areas of the brain that are first implicated are the striatum and neocortex. Neurodegeneration affects first the caudate nucleus and then the putamen. Disruption in the basal ganglia is associated with medium spiny neurons becoming dysfunctional in patients with parkinson's disease (Perandones et al., 2010).

In more advanced stages of huntington's disease, also other brain areas are affected, such as the hippocampus, hypothalamus, the cerebellum, the amygdala as well as some nuclea. The neurons that are mostly affected in huntington's disease are the striatal projection neurons (Perandones et al., 2010). A different neurogenesis may also relate to the disease.

Epilepsy is found to be more apparent in the juvinile case of huntington's disease.

In addition, mood and anxiety disorders are frequently seen in huntington's disease. Also, at later stages of the disease, psychosis is not uncommon.

In the early parts of the disease, cognitive deficits, such as attention problems, working memory impairments, and poor decision making can be seen.

Later in the course, deficits in everyday capabilities become evident, because of more severe motor disfunctions, such as postural instability (Perandones et al., 2010).

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