A study of apolipoproteins E and A-I in cutaneous amyloids

Background Apolipoprotein E (apoE) is present in a variety of biochemically different amyloid deposits, including Alzheimer's disease, systemic amyloi dosis and primary cutaneous amyloidosis (PCA). Among the three closely rela ted alleleic forms of apoE, the epsilon4 allele is linked to Alzheimer's di sease. Apolipoprotein A-I (apoA-I), another apolipoprotein, is also found i n senile plaques of Alzheimer's disease and in amyloid of aortic atheroscle rotic plaques. Furthermore, apoA-I has recently been found to be associated with hereditary cutaneous and cardiac amyloidosis. Objectives To determine whether the apoE epsilon4 allele is associated with increased risk of PCA and whether apoE and apoA-I are present in PCA and c ommon secondary cutaneous amyloidosis (SCA) (i.e. basal cell carcinoma, Bow en's disease and seborrhoeic keratosis). Methods We examined the apoE genotype in 57 Chinese patients with PCA and 5 8 normal healthy control subjects of similar age. In addition, immunohistoc hemical staining was performed to determine the localization of apoE and ap oA-I in skin tissues from 15 patients with SCA and 15 with PCA. Results The frequency of the epsilon4 allele in the PCA group was not signi ficantly higher than that in the control group (8.8% vs. 6.9%, P > 0.05). A poE was present in amyloid deposits in both PCA and SCA, but apoA-I was not detected in these cutaneous amyloid deposits. Conclusions ApoE is also a component of amyloid deposits in SCA. Although t he genetic susceptibility of certain apoE isoforms may not be a crucial fac tor in the development of PCA and, although apoA-I is not associated with a myloid deposits of PCA and SCA, the role of apolipoproteins in amyloidogene sis deserves further scrutiny.