Spinocerebellar ataxia type 7 (SCA7): family princeps history, genealogy and geographical distribution.

We conducted a 320 year retrospective survey of the history and genealogy of a large Brazilian family with SCA7. The ancestral couple was from the State of Ceará, Brazil, and the genealogical tree was composed of 577 individuals, including 217 males (37.6%), 255 females (44.1%) and 105 individuals of unknown sex (18.1%). Based on collected information, the 118 individuals consistently affected were distributed in generations IV (n=2), V (n=28), VI (n=57), VII (n=25) and VIII (n=6) of the genealogical tree. Sixty affected members are alive, 37 of them (61.6%) live in the Northeast region, 12 (20%) in the Southeast, 9 (15%) in the Center-West and 2 (3.3%) in the North. This genealogical survey was based only on 4 of the 10 children of the ancestral couple since the destiny of the remaining 6 is unknown. We propose that other Brazilian families with SCA7 may have the same genetic origin.