Huntington Disease

Huntington disease, an autosomal dominant inherited neurodegenerative disorder, is characterized by the clinical triad of involuntary choreiform movements with cognitive and behavioral disturbances. It occurs due to cytosine, adenine, and guanine (CAG) trinucleotide repeats on the short arm of chromosome 4p16.3 in the Huntingtin () gene. This mutation leads to an abnormally long polyglutamine expansion in the HTT protein's N-terminal fragment, which leads to neurodegeneration. The expansion also causes the HTT protein to be more prone to aggregation and accumulation, which mitigates protein folding. Huntington disease commonly affects patients between the ages of 30 to 50. However, the longer the CAG repeats, the earlier the onset of symptoms. The term juvenile Huntington disease 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 Huntington disease and can be confirmed by DNA determination. Premanifest diagnosis can determine if they carry the gene in patients at risk for the disease. The disease has no cure, and affected patients tend to be entirely dependent on their caregivers as the disease progresses. Therefore, treatment aims to improve the quality of life and decrease complications. Pneumonia is a common cause of death, followed by suicide.