The Sound of Striped Hooves

Around a year or so ago, an interesting thing happened to me. I was in the car with my mother, we were driving down the motorway, and there was a car pulling a horsebox in front of us. We were going rather faster than the horsebox, and as we passed it, I looked inside and saw… a zebra. It was only a glimpse and it confused the hell out of me for a moment, but I am still sure it was a zebra, not a horse, inside that horsebox.* At first I was slightly worried I might be going mad, but my mother pointed out that there are plenty of zoos and animal parks around the place and presumably they must transport their zebras somehow.

Folk of a medical persuasion will probably see where I am going with this, but I promise it is an entirely true story, the proof of which is that it took months and months for it to occur to me that I could use it on this blog. What can I say? I am slow.

Healthy people are probably wondering why I am blathering about hoofed african mammals instead of my usual cheery chat about tumours, but fret not. All shall be revealed.

A zebra is, as Wikipedia (and, I believe, Scrubs) so nobly tells us, the medical term for a surprising diagnosis, which rather begs the question of what we should call those stripey ponies running around in nature documentaries. It comes from the aphorism that when you hear hoofbeats behind you, you don't expect to see a zebra. This is a wise observation which is totally inapplicable to anyone who lives in the African plains, but as it was coined by an American doctor in the 1940s, this oversight may perhaps be forgiven. The point is that when a doctor is presented with a set of symptoms which may be caused by a common illness or an uncommon one, the logical assumption should be that the patient most likely has the more common illness - even though there may be a temptation to go with the more dramatic diagnosis.

I have noticed this idea of being a medical zebra popping up in a few blogs by other people with rare pituitary tumours, particularly in those with Cushing's disease - possibly this is related to the fact that one of the symptoms of Cushing's is the development of dramatic stretchmarks of a stripey and thus zebra-like nature. A few further examples - here, here and here.

A group of Cushing's sufferers at a recent conference.

I guess I count as a medical zebra myself; my symptoms of hyperthyroidism such as tachycardia, hair loss and frenzied blogging** would normally be considered as indicating Graves disease or something - and even when the more common thyroid malfunctions were ruled out, it was considered more likely that I had a condition called Resistance to Thyroid Hormone than thyrotropinoma. But no, my body had picked the most unusual way it could think of to break down, and I was neither a horse, nor a pony, deer, mule, donkey, nor any one of a number of hoofed creatures which are more common in the UK than zebras.

Neighbours of Lord Rothschild may not only have expected to see zebras when they heard the sound of hoofbeats, but also had to leap out of their way.

Medical zebras are a tricky subject, on the whole, and there's obviously a balance to be struck. While it can be frustrating for those of us with unusual conditions to think that we waited a long time for a diagnosis, it would be far worse if doctors went around ignoring common diagnoses in favour of the weird ones. Equally though, doctors should be aware that just because something's weird and unusual doesn't mean it's not sitting in front of you - as anyone who's come face-to-face with Boris Johnson could tell you.

It's enough to make you wonder how rare your condition would have to be before you were considered a medical okapi...

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*Unless someone had painted a horse to look like a zebra. Which would be a pretty weird thing to do.

**Hint: one of these is not actually a symptom.