"WHEN .. iron HAS been shown to BE a .. problem"

That is the problem with far far too many of these posts.  Iron is not
in itself a problem, we would die without it.  Toxic levels of iron is
the problem when we are talking about it being a cause of something. 
Iron shows up with many disorders not as a cause but as a side effect,
the dog and tail question.  Many disorders cause injury to tissue in
which case iron is liberated from tissue stores and appears as such when
testing blood and other tishues.