Detection of presymptomatic carriers of Huntington's chorea.

Laterality of thumb opposition and handedness were determined in three groups of subjects: patients with Huntington's chorea (n = 18), asymptomatic offspring of patients (n = 40), and asymptomatic siblings of patients over 50 years of age termed 'escapees' (n = 17). 100% of patients and 55% of young at-risk offspring had crossed laterality of thumb opposition and handedness. Only 2 (11.8%) of the 'escapees' had crossed laterality. Crossed laterality may be associated with symptomatic presymptomatic Huntington's chorea.