Richard Feynman in What Do You Care What Other People Think? says something similar happened with his first wife Arlene who contracted tuberculosis. If we trust his account, then it went something like this:

Arlene presented with bumps on her neck and the doctors couldn't figure it out. In his free time Feynman read medical textbooks in the Princeton library, and the first thing in the book is tuberculosis, which it describes as being "very easy to diagnose." Feynman assumes if its so easy and the doctors can't figure it out then it has to be something much rarer, something like Hodgkin's lymphoma. He asks the doctor about Hodgkin's, and the doctor admits it is a possibility.

> When she went to the county hospital, the doctor wrote the following diagnosis: “Hodgkin’s disease?” So I realized that the doctor didn’t know any more than I did about this problem.

After several months the doctors order a biopsy of her neck and pretty easily confirm it was tuberculosis. Feynman concludes that he made a huge mistake assuming they ruled out the easiest diagnosis.