The highest prevalence in the world has been described in the Lake Maracaibo region of Venezuela encompassing 18.149 individuals spanning 10 generations. There are 9,162 males and  8,256 females and 731 individuals of unknown gender.  They represent a high genetic risk population. 83 kindreds were analysed. The additive genetic heredability was estimated as of 38 % and environmental variance was estimated as of 60 %. The majority of Venezuelan Kindreds descend of a woman in 19th century who died of HD and transmitted the altered allele. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HD occurs with relentless progression and significant variability in symptoms and age of onset in families and people with identical CAG repeat length in the huntingtin gene. This population have provided genetically relevant data. The repeat size of longer allele varies from 14 to 86 repeats in this population. The study reports that the larger the size of the repeat, the earlier the age of onset.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The average age of onset in this population is 34.35 years of age (±10.07), earlier than in Canada (40.36 ± 12.97) and America (37.47 ± 13.28). This evidence suggests the presence of other deleterious modifying genes not associated with HD and environmental effects (extreme poverty, marginal diet and Lake Maracaibo pollution). Huntington gene is subject to somatic mosaicism. Repeat size expansion has been found in seminal and testicular fluid and brain tissue. (Wexler et al, 2004).