What is the common feature of Huntington's disease?

Huntington's disease is characterized by autosomal dominant inheritance due to a CAG repeat expansion in the HTT gene, which encodes the huntingtin protein. The presence of this expanded CAG repeat leads to the production of a mutant form of the protein that is toxic to neurons, particularly in the basal ganglia, causing the characteristic motor, cognitive, and psychiatric symptoms associated with the disease.

A key aspect of Huntington's disease is its late onset, often occurring in mid-adulthood, and the fact that the severity of the disease correlates with the number of CAG repeats present. While the presence of environmental factors may influence disease expression, the primary and defining genetic feature is the autosomal dominant nature of the CAG repeat expansion. This makes the understanding of the disease predominantly genetic and inherited in a specific pattern rather than influenced by recessive mechanisms, X-linked mutations, or environmental triggers.