I posted this link from ME Research UK on an earlier thread; misdiagnosis involving ME:
http://www.meresearch.org.uk/information/publications/misdiagnosis-on-a-grand-scale/
Two scientific papers noted in this link regarding misattribution of ME to 40% of patients in study #1, and 54% of patients in study #2.
ME Research UK also receives direct contact from about 400 people/year who first diagnosed with ME, have been re-diagnosed with other diseases such as: "Addison's, MS, sleep apnoea, primary mitochondrial disease, primary liver disease, and paranoid schizophrenia."
One can assume these people do not receive treatment until re-diagnosed.
ME Research UK calls ME "a convenient lay-by for clinically complex cases that don't fit into any category."
We can add haemochromatosis to this list.