An affliction that causes considerable problems for people who become so expert at their chosen line of study or research that no one can understand those who have expertitis.
I've become so expert at dealing with highly specialized cases of wrongfully arrested cases that I have difficulty teaching my craft to others. That's Expertitis.
That's problematic because the truth is that a law degree is of no use to any would be expert who wants to specialize in the sort of cases that I deal with.
I have a 100% success rate, but "Expertitis" makes it difficult for me to understand why amateurs can't do what I do.