Huntington's disease belongs to a class of inherited neurological disorders that are caused by the presence of a polyglutamine expansion in apparently unrelated proteins. In Huntington's disease, expansion occurs in the huntingtin protein. Together with the characteristic formation of aggregates in the diseased state, several post-translational modifications affect huntingtin during the pathological process and lead to the dysfunction and eventual death of selective neurons in the brain of patients. These mechanisms are not completely described but could involve the gain of a new toxic function as well as the loss of the beneficial properties of huntingtin.