APOE ε4 was the only variant segregating 93 (22.6%) of families, Among the AD‐FBS cohort, 64 (32.5%) families had only segregation with APOE ε4, and in the EFIGA cohort, 29 (13.5%) families had only APOE ε4 segregation. The gene discussed is APOE; the disease is Alzheimer disease.