Unfortunately, from my understanding Doctors don't necessarily diagnose for accuracy, they often diagnose to limit liability.

They aren't going to take a stab at an uncommon diagnosis even if it occurs to them, if they might get sued if they're wrong.

Edit: I'm not trying to say Doctors deliberately diagnose wrong. Just that if there are two possible diagnoses, one common that matches some of the symptoms and one rare that matches all symptoms, doctors are still much more likely to diagnose the common one. Hoofbeats, horses, zebras, etc