Molecular genetics of common diseases

Abstract

Coronary heart disease, essential hypertension, diabetes mellitus, senile dementia, manic depressive psychosis, schizophrenia, and other common diseases of adults tend to cluster in families. The familial aggregation of these disorders is rarely caused by a single gene defect; rather, it results from the cumulative interaction of a number of genes with environmental factors. These disorders are therefore said to show multifactorial or polygenic inheritance. The risk of polygenic disease in first degree relatives is generally less than the 1 in 4 risk for mendelian recessive disorders, being about 5-10% (table I). The risk of multifactorial disease, however, varies from one disease to another and from family to family. Within a family the risk depends on the severity of the disorder in the proband, the number of affected family members, and the contribution from environmental risk factors. © 1987, British Medical Journal Publishing Group. All rights reserved.