And The Vet Said...

Pemphigus Foliaceus

We recently saw two interesting and unusual skin conditions in our practice. These conditions turned out to be pemphigus foliaceus. This skin disorder is seen more commonly in dogs than in horses or cats but it is still an uncommon condition in all three species. It was very unusual to see two cases within a short time period.

Pemphigus foliaceus is an autoimmune condition. The disease is characterized by skin erosions, ulcerations, and thick encrustations of the skin and mucocutaneous junctions. The condition also occurs in humans with similar skin appearance.

Autoimmune disease basically means the ability of the immune system to recognize the "self" marker is lost, and it begins to attack and reject the body's own tissue as foreign. Unfortunately, autoimmune diseases remain among the most poorly understood of any category of illness.

Both of the horses we was presented with had swollen legs and a fever. These are also the clinical signs that are consistent with ehrlicia equi now known as anaplasma phagocytophila. We see this condition very often in our practice and we initially thought that was the case with these horses as well. In fact, one of these two horses was found to have morulae in a blood smear that was taken. This was consistent with anaplasma phagocytophila. The horse was treated for this disease using oxytetracycline. The horse seemed to respond initially, however it continued to have a peculiar scaly inflamed appearance to the skin. The horse was also loosing hair and the skin was thickened. It continued to run a temperature and was lethargic. It was at this point we began to wonder if we may be dealing with something other than anaplasma phagocytophila. A skin biopsy was performed and the result was pemphigus foliaceus.

The other horse had also been treated for anaplasma phagocytophila and seemed to respond somewhat; however it too, had this same peculiar skin appearance similar to the other horse. Blood tests showed a chronic infection was going on. This horse was continued on antibiotics and anti-inflammatory agents. A skin biopsy was also performed on this horse. It did not come back positive for pemphigus foliaceus, however this could have been due to the long term antibiotics and anti-inflammatory agents this horse had been treated with. The skin was so similar to the other horse with the positive diagnosis that we were very suspicious that it was the same for this horse.

Dexamethasone is the standard treatment for pemphigus foliaceus. Both of these horses were started on this drug at a decreasing dosage and they both responded very well.

One of the horses had lost a considerable amount of weight, and had some muscle atrophy as a result of the illness and weight loss. I am pleased to report at this point in time both horses are doing very well and have gained weight. The skin in both is also returning to a more normal appearance.

These were very interesting cases and unusual to see in such a short time frame. Please contact your veterinarian if you see any unusual skin conditions as many of these horses are mistakenly thought to have a fungal or bacterial condition that is thought will respond to topical treatments or washes. The sooner the proper diagnosis is made the better for all involved.