Apolipoprotein E genotypes in AA and AL amyloidoses

Apolipoprotein E (apoE) is associated with senile plaques in Alzheimer's disease (AD), and present in amyloid deposits in a variety of systemic amyloidoses. Recently, studies have shown that apoE4 allelic frequency is increased in patients with sporadic and familial late-onset AD and that apoE4 may represent a susceptibility gene for late-onset AD. We addressed the issue of whether a similar association of apoE4 exists in a number of systemic amyloidoses. Tissue was obtained from control subjects, AD patients, familial Mediterranean fever (FMF) patients, amyloid A (AA) amyloid secondary to juvenile chronic arthritis (JCA), and amyloid of the light chain type (myeloma or AL). There was a strong correlation of the apoE4 allele with sporadic and late-onset AD, but no significant increase in apoE4 with other amyloidoses. These data suggest that whereas apoE4 may be a risk factor in AD, it is not in other amyloidoses. However, given the association of apoE with all these amyloidoses, the possibility cannot be excluded that this apolipoprotein could be involved in systemic amyloidoses on an isotype non-selective basis.