The single gene disorders (see 1.1.2) confirm the importance of genetic influence on blood pressure. However, the approaches outlined have been successful because a clearly defined hypertensive phenotype could be identified and a clear pattern of inheritance could be assigned. This type of model-specific pedigree analysis is less likely to be successful in the general trait of essential hypertension where clear Mendelian models of inheritance cannot readily be assigned because there may be variable penetrance of susceptibility genes [24]. In addition, age of onset of the trait may be variable, or there may be an absence of environmental stimuli or other gene interactions necessary to disclose the phenotype.
The heterogeneity of potential genetic mechanisms and environmental influences for hypertension, coupled with interindividual variability in antihypertensive efficacy, particularly among ethnic groups [41], has prompted researchers to ensure homogeneity in the study populations of individuals with essential hypertension. In some of the larger programmes currently under way this has led to identification of individuals who, despite having a lean body build with low levels of alcohol (ethanol) consumption, are severely hypertensive, and are representative of those with maximal genetic influence upon blood pressure.
© 2001 Alexander Binder