I enjoy complicated dermatology cases, but many veterinarians find them unbearably frustrating. The reason behind this is simple. Owners want quick answers and permanent solutions, particularly when it comes to problems affecting the skin, and veterinarians don’t like to disappoint. Clients seem more willing to understand the need for a methodical work up when pets are “sick,” a description that sometimes doesn’t seem to apply when dealing with dermatological lesions.

Pemphigus foliaceus is a perfect example of this type of challenge. The disease often starts with pimple-like lesions around the head (the inner surface of the ear flap is predisposed) and feet. Because the pimples quickly rupture, the crusts that are left over are what tend to be observed by owners. Dogs and cats are generally not itchy, unless they develop a secondary skin infection, and feel well otherwise. Some pets present with skin lesions across most of their bodies, either because of owner inattention or a more aggressive variant of the disease.

Keep in mind that innumerable skin diseases cause similar symptoms, many of which are more common than pemphigus, so the veterinarian’s first job is to start winnowing down the list. I do this by running a skin scraping for mites, a fungal culture for ringworm, and skin cytology for infections. At this point we may get sidetracked for a few weeks. If I find an infection I’ll treat it, but if it’s being caused by pemphigus the lesions will only partially resolve. I may also put the dog or cat on a broad spectrum parasiticide like selamectin to rule out some of the external parasites that can be hard to diagnose, but this won’t have any effect on a case of pemphigus. Finally, fungal cultures take a few weeks to complete, and I try to wait on those results before proceeding.

By this point we’re usually 2-3 weeks out from our first appointment. During the recheck, all but the most understanding of clients are a little frustrated. They’ve spent a significant amount of time and money on their pets with little to show for it. Hopefully I’ve done a good job preparing them for the complexities of dermatology and they’re eager to move on to the next diagnostic step – a general health work-up including blood work and a urinalysis followed by skin biopsies.

The lab work is needed to rule out systemic illnesses. With pemphigus, the results are usually unremarkable but still serve the purpose of preparing for the safe, long-term use of medications to control the disease. The only way to definitively diagnose pemphigus is to send off multiple skin biopsies for review by a pathologist. When they see a characteristic change in a particular layer of skin, they can then make the call.

Pemphigus foliaceus is an autoimmune disease that is often worsened by exposure to sunlight. It is caused by the body attacking cells called desmosomes that connect other skin cells called keratinocytes. Treatment involves the use of immunosuppressives – usually steroids alone or in combination with other drugs like cyclosporine or azathioprine depending on the pet’s response. Pemphigus may be instigated by the use of certain types of medications, but the cause of most cases goes undiagnosed and is suspected to have genetic underpinnings.

Some patients may eventually be able to be weaned off immunosuppressive medications, but many dogs and cats require lifelong therapy to control the disease. The goal is to find the lowest doses of the drugs with the least side effects for that individual, a process that requires good communication between owner and veterinarian, quick response to flare-ups, regular rechecks, and continued large doses of patience.

Dr. Jennifer Coates

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