The cause of the accumulation of total iron in the substantia nigra of patients with PD is not well known, but several possible factors have been proposed, such as blood–brain barrier dysfunction [109,110]; upregulation of some iron-storage proteins such as lactoferrin [111] and transferrin [112,113]; Increased expression of DMT1 in dopamine neurons [114]; ceruloplasmin dysfunction and so on (Figure 3). This evidence concerns the gene LTF and Parkinson disease.