Apolipoprotein E genotype and psychosis.

Apolipoprotein E (Apo E) is a protein with 299 amino acids coded by a gene on chromosome 19. The three major isoforms of Apo E (Apo E2, Apo E3, and Apo E4) are products of three alleles (Apo E-e2, Apo E-e3, and Apo E-e4). Inheriting the e4 allele of the Apo E is associated with increased risk of developing Alzheimer's disease (AD). Many papers show linkage of the presence of Apo E-e4 and late-onset AD (Corder et al 1993; Nalbantoglu et al 1994; Noguchi et al 1993; Saunders et al 1993; Strittmatter et al 1993; Yoshizawa et al 1994); however, the frequency of the Apo E-e4 was low in "schizophrenics with progressive dementia" and late paraphrenia (Martiuoli et al 1995; Howard et al 1995). In contrast, Harrington et al reported that Apo E-e4 allele frequency was increased in patients with schizophrenia (Harrington et al 1995). Thus, we determined the Apo E genotype in patients with schizophrenia whose status had been strictly diagnosed and investigated the association of the Apo E-e4 allele and schizophrenia.