The diagnosis of Huntington's disease.

We investigated all patients in Maryland reported to have Huntington's disease (HD), and found considerable diagnostic inaccuracy. Fifteen percent of cases reported as HD actually had some other diagnosable condition; 11% of cases that met diagnostic criteria for HD had been given some other diagnosis. Diagnostic errors could be reduced by documentation of the family history by systematic interviewing of relatives and by demonstration of the characteristic disorder of voluntary movement in addition to chorea.