One study investigating inherited gene mutations in AD found in-frame UNC13C deletions for two dementia patients, whereas this mutated variant was missing for two healthy family members; however, the small sample size and presence of confounding variables such as the presence of apolipoprotein E (APOE) ɛ4 in these subjects warrants more research on the nocuous effects of the UNC13C mutation in AD [37]. Here, APOE is linked to Alzheimer disease.