The garrulous patient that keeps you entertained till you realise he is a manic depressive; the patient who attends many times with non-specific general complaints till the penny drops in a chilling instant that there is probably a malignancy present. Unfortunately, this moment of enlightenment is often imperceptible.
Continuing care by a single doctor is one of the more sensible mantras of general practice. When I was an intern, the team consisted of a consultant, a senior registrar, a research registrar, a senior house officer on rotation, a senior house officer not on rotation (a particularly pathetic species), two other interns, and about 60 cajillion medical students, and still nobody knew anything about the patients.
But there is a Dark Side; familiarity can obscure any gradual changes and prevent us from recognising these critical moments.
Our concept of time is too coarse; when we look in the mirror each day we don't see ourselves growing older and, similarly, if we see a patient too often all but the most obvious changes are invisible. Then that infuriating day comes when the partner/locum, blessed with the fresh, unprejudiced eye, says: 'Hey, that guy's a classic case; how did you miss that he is hypothyroid/acromegalic/growing two heads?'
Well, it's easy to miss it, you smug bastards, and your time will come. The second head starts as a tiny bump, classically on the right shoulder; two weeks later it's a wee bit bigger, then slowly over the years it grows until before you know it, like Robert Browning envying you guys waking in England and seeing one morning, 'unaware/That the lowest boughs and the brushwood sheaf/Round the elm-tree bole are in tiny leaf', you've got a fully grown second head giving you cheeky backtalk.
By now a painless cure is no longer possible; you are so steeped in gore/that to go back were as bloody as to go o'er. The axe must be scalpel sharp, or else you will have to hack and hack and hack, and all the while the second head is ducking and weaving, screaming and cursing and wheedling.
And trying to persuade you that two heads are definitely better than one.