Progressive familial heart block
Two types of familial heart block have been recognized in certain Afrikaans-speaking families distributed over South Africa. These autosomal dominant conditions are progressive, and in the absence of treatment to regulate heart rate the defect of cardiac conduction causes syncope and sudden death. Type I progressive heart block was delineated in a family in which numerous cardiac deaths (22 in three generations) had occurred. Electrocardiographic investigations of 55 further family members demonstrated conduction defects in 31. Type II progressive heart block was recognized in another family with a strong history of sudden deaths, and electrocardiographic studies have revealed 10 affected individuals. These family studies are not yet complete, and the magnitude of the problem has not been determined. However, it is clear that both types of conduction abnormality have serious medical implications, have been spread widely by the founders, and are at present to be found in numerous predominantly Afrikaans-speaking families. The type I founder family can be traced back to the marriage in 1735 between a male immigrant from Lisbon, Portugal, who arrived at the Cape in 1696, and a woman of French descent. They settled in the Eastern Cape, and a large number of descendants from three branches of the family through at least six generations still live in the area. From the fourth generation onwards the family spread widely over South Africa and beyond. The founders of the type II family are the offspring of a Dutch immigrant from Amersfoort, who arrived at the Cape in 1713 and married a local woman in 1720. This couple had 4 children and the condition can be traced to a branch of the family founded by a son who settled in the Eastern Cape, where many descendants still live.
•(Ignatius Ferreira)
•(Jan Izak van der Bank)
https://www.geni.com/projects/South-Africa-Founders-Effect/18512
