A post-mortem study of five Alzheimer's and five control brains has revealed the presence of iron-containing microglia in the subiculum of the Alzheimer's brains only. The subiculum lies within the hippocampus, a vital memory region affected early in Alzheimer's. None of the brains of those not diagnosed with Alzheimer's had the iron deposits or the microglia, in that brain region, while four of the five Alzheimer's brains contained the iron-containing microglia.
The microglia were mostly in an inflamed state. Growing evidence implicates brain inflammation in the development of Alzheimer's.
There was no consistent association between iron-laden microglia and amyloid plaques or tau in the same area.
Obviously, this is only a small study, and more research needs to be done to confirm the finding. However, this is consistent with previous findings of higher levels of iron in the hippocampi of Alzheimer's brain.
At the moment, we don't know how the iron gets into brain tissue, or why it accumulates in the subiculum. However, the researchers speculate that it may have something to do with micro-injury to small cerebral blood vessels.
This is an interesting finding that may lead to new treatment or prevention approaches if confirmed in further research.
 . Activated iron-containing microglia in the human hippocampus identified by magnetic resonance imaging in Alzheimer disease. Neurobiology of Aging [Internet]. Submitted . Available from: http://www.sciencedirect.com/science/article/pii/S0197458015003061