In particular, FERRITIN levels in cerebrospinal fluid (an indicator of iron storage capacity) are very significantly higher in carriers of the major LOsAD risk allele, the ε4 allele of the gene APOE (APOE4), and predict conversion from mild cognitive impairment (MCI) to Alzheimer’s disease (Ayton et al., 2015). The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.