You may have come across news headlines with something like "woman diagnoses herself with rare disease."
If you take this statement at face value, you might think "hmmm so this woman, out of the blue, just diagnose herself with a rare disease."
What most people don't often realize is that for a rare disease to be considered, she must have gone through many different doctors who diagnosed her with various diseases, but she feels that neither of them accurately describe her symptoms. She might do some research, and came across a rare disease that perfectly describe her symptoms.
A more accurate (but more verbose) headline would be "doctors failed to accurately diagnose woman with rare disease".
Takeaway? Think twice before taking anything at face value.