Inheritable causes and risk factors of Alzheimer's disease

A multifactorial etiology underlies the majority of cases of Alzheimer's di sease (AD). Both ill-defined environmental and genetic factors contribute t o the development of the disease. Allele epsilon 4 of ApoE is a genetic ris k factor. Its presence increases the risk of developing AD. However, presen ce of e4 is neither necessary nor sufficient for the disease to arise. Apar t from the common multifactorial forms of the disease, there are rare varia nts which are inherited as Mendelian traits. To date three genes are known that can be mutated in these rare farms of ED. Of these, mutations in the g ene presenilin 1 on chromosome 14 are most frequent. In addition, mutations in the gene presenilin 2 an chromosome 1 and in the amyloid precursor prot ein gene (APP on chromosome 21) occur in autosomal dominant AD. This articl e reviews our present knowledge of the genetics of AD and discusses its rel evance for patients with AD and their relatives.