Genetics, geography and intelligence in the torsion dystonias

Personal study of 137 individuals with torsion dystonia (TD) in 92 families, and review of 476 reported cases indicate that there are at least two hereditary forms of TD in addition to acquired dystonia. Autosomal recessive TD, with onset generally between the ages of 4 and 16 and rapid initial course, has been found in highest frequency in the Askenazim. Autosomal dominant dystonia is more variable in its time of onset and course and torticollis is frequently an early symptom. Families with this form are present in several populations. The psychometric performance of patients with autosomal recessive TD is superior to that of controls. In contrast, families in which the dominant form is segregating often contain individuals with below average IQ but this may be a social effect and reflect a limited choice of mates by members of such families.