When the Horses Aren’t the Answer: Sometimes the Zebra Really Is the Diagnosis
When I was in veterinary school, our professors repeated a phrase so often that it became almost impossible to forget:
“When you hear hoofbeats, think horses, not zebras.”
It was a simple way of teaching us one of the most important principles in medicine: common things are common. When a patient has a particular set of symptoms, we should start by considering the most likely causes rather than immediately jumping to the rarest disease we can remember from a textbook.
It’s good medicine.
But every veterinarian eventually learns the other half of that lesson:
Sometimes, the hoofbeats really are coming from a zebra.
That was the case with Aria.
A Dog With a Skin Problem That Wasn’t Getting Better
Aria was an eight-year-old Shepherd mix who came to EVS Pet Urgent Care because of ongoing skin problems.
At first glance, this sounded like an incredibly common veterinary complaint. Dogs with allergies frequently develop secondary bacterial or yeast infections, which can cause redness, itching, crusting, hair loss, and uncomfortable skin lesions.
So my first thought was exactly where it should have been: allergies with a secondary skin infection.
But there was something about Aria's history that made me stop.
She had already been treated for allergies for months.
She had received multiple courses of antibiotics.
She had been given different allergy medications.
Her family had gone through food trials and other standard treatments we commonly use for allergic skin disease.
And despite all of that...
Aria wasn't getting better.
She was getting worse.
That changes the way we think about a patient.
When Treatment Isn't Working, It's Time to Reconsider the Diagnosis
One of the things I didn't fully appreciate when I opened EVS Pet Urgent Care was how often we would become a second-opinion—or sometimes even a third- or fourth-opinion—practice.
I'll admit that can feel intimidating.
You can't help but think, “If other veterinarians have already been working on this, what am I going to see that they didn't?”
But there's an important principle in medicine: disease changes over time.
Sometimes, as a disease progresses, the picture becomes clearer.
And when I examined Aria, I noticed something that made me think we might be dealing with something very different from routine allergies.
She had lesions in classic locations—particularly around her feet—that raised my concern for a rare condition called hepatocutaneous syndrome.
Hepatocutaneous syndrome is an uncommon disease associated with significant underlying liver abnormalities and characteristic skin changes. It is not something most veterinarians will see frequently in practice.
In fact, I had learned about it in veterinary school. I had read about it in textbooks.
But I had never actually seen a case myself.
And that's important.
Because if Aria had walked into my exam room several months earlier, before the disease had progressed and before these characteristic lesions had developed, I might have followed the same path of treating the much more common causes of skin disease.
That's not bad medicine.
That's medicine.
We treat the likely causes first. When a patient doesn't respond as expected, we reassess and broaden our thinking.
Looking Beyond the Skin
I talked with Aria's family about my concerns, including the fact that I was considering something much less common than allergies.
They agreed to move forward with baseline diagnostic testing.
Her bloodwork provided an important clue: Aria's liver enzymes were markedly elevated.
That finding, combined with her history and the appearance and location of her skin lesions, made hepatocutaneous syndrome much more concerning.
The Zebra
At EVS, our goal is not to replace your primary veterinarian or to chase rare diseases unnecessarily.
In fact, quite the opposite.
We believe in starting with the most likely explanations and using a thoughtful, systematic approach to diagnostics and treatment.
But when a pet isn't responding to appropriate treatment, that's when we need to ask:
Is the diagnosis correct?
Is there something else going on?
Are we treating the symptom instead of the underlying disease?
For Aria, the answer was yes.
Because her case was beyond what we could definitively diagnose and manage in an urgent-care setting, I referred her to a veterinary internal medicine specialist.
The specialist performed an abdominal ultrasound, which revealed characteristic changes in Aria's liver. The appearance was described as having a “Swiss cheese” pattern—an imaging finding associated with hepatocutaneous syndrome.
The internal medicine specialist agreed with our presumptive diagnosis and began appropriate therapy.
We had our zebra.
What TV Medicine Gets Right—and Gets Very Wrong
Her case actually reminded me of one of my favorite medical shows, House.
For an hour, the doctors would work through a mysterious case. They'd start with the obvious possibilities. Tests would come back negative. Treatments wouldn't work. The diagnosis would get progressively more complicated.
And eventually, Dr. House would have some dramatic epiphany, usually accompanied by a handful of Vicodin and an impressive ability to solve the case without saying much at all.
There was no Vicodin involved in Aria's case.
And there was certainly no magical epiphany.
What there was instead was something much less dramatic but far more important:
Observation.
History.
A physical examination.
Diagnostic testing.
Recognizing when treatment wasn't working.
And being willing to reconsider the original diagnosis.