Isn’t it frustrating how the most complex and rare  conditions can turn up when you are least expecting them? I know that common things occur commonly, but that doesn’t mean that everything that comes into your morning surgery will necessarily be common. As you well know.

You were probably exposed to a similar ritual as me when you were at medical school. I can still picture it. A haughty teaching hospital doctor – probably quite junior, but with all the arrogance of some of his seniors – was teaching a group of us students. I was cornered and asked what I thought the rash covering the patient in front of us might be.

I was flustered, not to mention clueless, and named something exceedingly rare – tertiary syphilis. I don’t recall the full details of my ignorance, just that it was pretty deep.

At that my teacher pointed out of the window at a bird on a distant chimney pot and asked me what I thought it was.

Before I could say a word he said:

‘I suppose you’ll be telling me it’s a hummingbird, won’t you. Never forget that common things occur commonly. That’s a pigeon, and this is not tertiary syphilis.’

Ignoring the irrelevant fact that I was pretty sure that the bird in question wasn’t a pigeon, the point was well made.

Common things occur commonly. Don’t diagnose hummingbirds when the trees are full of pigeons. Don’t assume it’s a zebra when it’s just a pony. Don’t see a lynx when it’s just a tabby. And so on.

Except that hummingbirds, or their diagnostic equivalent, do have the nasty habit of coming in to consult GPs and we have to know when and how to spot them. Even if we don’t realise they are humming birds, we need to know when to request a second opinion.

All of us have seen cases that appear to be unique – the only one presenting in that particular way in the world. It’s not fair, is it? But it’s certainly interesting.

Looking back at my diaries, I can recall a morning surgery when I saw a woman who had brought in her young son for me to look at his tympanic membranes.

She then said ‘and while I’m here doctor…’ and presented me with a rash on her anterior calf. 

She said it had almost certainly come on while gardening, but I became absolutely certain that it was actually necrobiosis lipoidica.

Now, you may think there is nothing unusual about a case like that. However, when you think of how she presented, what her history was, and what the signs and symptoms were, and what my impression was, then the mass of variables is extraordinary. The task of the GP in having to spot the pattern among the complexity is much greater than we sometimes recognise. Somehow, we have to recognise the underlying patterns while avoiding the stereotyping that reduces our patients’ individuality.

One fact that we must never ever forget is that even the world’s rarest condition will affect a patient who has a GP.

Patients live in the community, not in tertiary care units, and the community is that bit of the medical universe that we all call home.

So when you look out of the surgery window and see that bird on the distant chimney pot remember that it might be a macaw. Even if it really is a pigeon, the next one along may not be. Tough, isn’t it.