Apolipoprotein E polymorphism and clinical disease phenotypes in Arab patients with schizophrenia

Apolipoprotein E (APOE) is polymorphic, and may be involved in the pathogenesis and clinical expression of schizophrenia. This study aimed to investigate the frequency of specific APOE genotypes and alleles in a schizophrenic Arab population and evaluate the association of specific APOE types with clinical phenotypes of the disease.

Two age-matched groups of subjects were studied: (1) healthy controls, n = 165; (2) patients with schizophrenia (SZ), n = 207. Each subject was evaluated for age and mode of onset of disease, family history of psychosis, disease severity and outcome over the years of illness. APOE genotyping was performed by a validated PCR-RFLP technique.

Genotype E3E2 and allele E2 were less frequent in the patients with schizophrenia (p = 0.04), and both APOE types tended to be more common in male than female schizophrenic patients (p = 0.08). Schizophrenic patients with a positive family history of psychosis had lower frequencies of genotype E3E2 and allele E2 (both p = 0.04). Genotype E3E4 and allele E4 were least common in patients with an age at onset of disease >31 years (OR: 5.5, 95% CI: 1.1-27.4), particularly in males.

APOE genetic polymorphism potentially influences susceptibility to schizophrenia and may be associated with aspects of its phenotypic expression, particularly gender, age of onset and family history of psychotic illness. This relationship of APOE with schizophrenia is likely to be race- and gender-specific.