Familial aggregation in developmental topographical disorientation (DTD).

A variety of brain lesions may affect the ability to orient, resulting in what is termed "acquired topographical disorientation". In some individuals, however, topographical disorientation is present from childhood, with no apparent brain abnormalities and otherwise intact general cognitive abilities, a condition referred to as "developmental topographical disorientation" (DTD). Individuals affected by DTD often report relatives experiencing the same lifelong orientation difficulties.

Hereditary chin trembling: a new family with exclusion of the chromosome 9q13-q21 Locus.

Hereditary chin trembling is a rare autosomal dominant condition that has been linked to chromosome 9q13-21 in one kindred. We describe a four-generation family with this condition and, using linkage analysis, have excluded the 9q13-21 region as causing the chin trembling in this family.