Diagnosis of patients presenting to a Huntington disease (HD) clinic without a family history of HD

About 9% of patients presenting to a Huntington disease (HD) clinic for evaluation of possible HD lacked a family history of the disorder. HD was the final diagnosis in 53 to 83% of these patients. As a group, HD-affected individuals without a family history of HD were older and had fewer CAG repeats than the average HD patient. Some patients presenting with chorea only had HD and others did not; patients developing a movement disorder after long-standing neuroleptic-treated psychiatric illness did not have HD.