This approach successfully identified the well-known apolipoprotein E (APOE) association with Alzheimer's disease (Pericak-Vance et al., 1991; Corder et al., 1993; Saunders et al., 1993), and the association of human leukocyte antigen (HLA) with many immune system disorders (Tomlinson & Bodmer, 1995). The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.