DDPAC was defined based on the cardinal symptoms of the syndrome found in family Mo. Investigation of DDPAC cases in family Mo shows non-specific pathological changes in a distribution that is consistent with the cardinal features of the disease. Genetic analysis identified a locus on chromosome 17q21-22 that produces this syndrome which is inherited as an autosomal dominant trait. DDPAC overlaps clinically and pathologically with a variety of named neurodegenerative syndromes and falls within the spectrum called frontotemporal dementia. The localization of the disease locus for DDPAC allows the testing of whether other familial neurodegenerative conditions also map to the same chromosomal regions. It seems possible that ultimately these conditions that have thus far been difficult to categorize will be subject to a nosology based on genetic etiology.