Huntington Disease

Excerpt

Huntington disease (HD), a neurodegenerative autosomal dominant disorder, is characterized by involuntary choreatic movements with cognitive and behavioral disturbances. It occurs as a result of cytosine, adenine, and guanine (CAG) trinucleotide repeats on the short arm of chromosome 4p16.3 in the Huntingtin (HTT) gene. This mutation leads to an abnormally long expansion of the polyglutamine in the HTT protein, which leads to neurodegeneration. The expansion also causes the HTT protein to be more prone to aggregation and accumulation that mitigates protein folding. HD commonly affects patients between the ages of 30 to 50 years. However, the longer the CAG repeats, the earlier the onset of symptoms. The term juvenile HD refers to the onset of illness before the age of 20 and is characterized by learning difficulties as well as behavioral disturbances at school.

Diagnosis can be made clinically in a patient with motor and or cognitive and behavioral disturbances with a parent diagnosed with HD and can be confirmed by DNA determination. In those patients who are at-risk for the disease, pre-manifest diagnosis can determine if they carry the gene. There is no cure for the disease, and affected patients tend to be entirely dependent on their caregiver as the disease progresses. Therefore, treatment is aimed at improving the quality of life and decreasing complications. Pneumonia is a common cause of death, followed by suicide.