The prolific Dave Wallace sent this one in.
Whilst having a medical history taken to address my SOBOE (Shortness Of Breath On Exertion) issues, the following (slightly embellished) conversation occurred.
Doctor: What are your limits on exertion?
Me: I can climb half-way up the back stairs, then need a rest.
Doctor: How many steps?
Me: 12… every time.
Doctor: You have OCD! (Obsessive Compulsive Disorder)
Me: No, it’s CDO – the letters gotta be in alphabetical order.
Doctor: Isn’t there a 12-step program for that?