When is a Spider Bite Not a Spider Bite?

All pet owners feel shocked when an apparently healthy animal suddenly turns up ill for no particular reason. Our Seal Point Siamese cat appeared one day with a swollen paw and a half-inch wide black mark on his skin, where he had pulled out the fur by licking at the sore spot. Ordinarily bursting with health, he was obviously uncomfortable. We bundled him off to the vet, who said it was a spider bite and gave him a shot of corticosteroid.

Madison loves to hunt spiders. He pulls off their legs and eats them the way you would eat a lobster.

But the "bites" recurred a dozen times over the course of the next four months. A paw would swell up the elbow, staying tender for days before diminishing. Then the swelling would appear in a different paw. We took him back again and again, eventually realizing that spider bites just didn't make sense. Our vets wouldn't consider another diagnosis, so we changed vets.

Cats don't show pain like dogs do, so we watched for subtle signs. Madison held his paw off the ground, touched it down tentatively, then shook it like he was trying to get a splinter out. For some Siamese cats, the touch-me-not rule is always in effect: Madison is a trusting hedonist who likes having his stomach rubbed. But now, if petted, he meowed a complaint and walked away. His tail became twitchy at the end joint. He was sometimes seized by a twitch, leaped around as if surprised, and then darted off. It was like the way your hand leaps up when you touch a hot stove.

I thought the trouble might be allergy-related. When shopping for a new vet, I questioned the veterinary receptionists on whether they had worked with allergies, and chose a new vet based on recommendations and her receptionist's knowledge. The veterinarian herself was so accessible that the receptionist asked her questions while I was on the phone the very first time.

Dr. Lauren Knoble, of Oakland's Lake Shore Veterinary Hospital examined Madison fully, feeling behind and under each limb, palpating his stomach and checking inside his mouth and ears. Her initial diagnosis was tentative but immediate. "I think Madison has pododermatitis," she said. She wanted to research it further. In the meantime, she put Madison on Prednisone to reduce the swelling. She also explained to us that Prednisone and Prednisolone (both steroids) have side effects: animals usually experience increased urination, much greater appetite and weight gain. We put Madison on a diet, monitoring his weight.

Dr. Knoble consulted by telephone with a well-known veterinary dermatologist. She showed us that Madison's paws, which looked dry, were actually irritated. Between the pads, the skin was pink and puffy. The pads had fine, dry-looking cracks running across them. Where the skin on his pads met the fur of his foot, his paws were chafed and sore. A biopsy returned a diagnosis of Pemphigus foliaceous.

Pemphigus foliaceous is an autoimmune disorder that can affect dogs, cats and people. Akita dogs and Siamese cats are more prone to pemphigus disorders than other pets, but German Shepherds, Chow-Chows, Bearded Collies, Shetland Sheepdogs, Dobermans, Newfoundlands, and other dogs can get them too. There are four varieties: Pemphigus foliaceus, pemphigus vulgaris, pemphigus erythematosus and pemphigus vegetans. They produce similar symptoms and are thought to have the same modus operandi, but are classified somewhat differently depending on the parts of the body affected.

In pemphigus disorders, the body begins to perceive its own cells as foreign bodies. The skin on Madison's paws, being different in structure and function from the skin surrounding them, was being treated by his immune system as an unwanted, invading substance. The immune system was attacking the skin on and around his paws, attempting to kill off what it perceived as a danger to the body.

While the origins of autoimmune disorders are largely unknown, it is thought that stress, injury or other illnesses may precipitate an autoimmune response that goes awry. Perhaps the initial problem was a spider bite that set off a dysfunctional reaction in the cat's immune system.

Pemphigus disorders have the same basic symptoms, although p. vulgaris may result in especially bad ulcerations over more of the body than the other forms of the disorder. In general, specialized skin (often mucus membranes) becomes scaly, sometimes with pimple-like sores or scabs. The skin may blister, and blisters may become infected.

Pemphigus erythematosus is thought to be a milder form of p. foliaceus, which often affects the paws and pads, and the nail beds in cats.

Pemphigus vegetans is distinguished from the other pemphigus disorders by the formation of wart-like growths that become ulcerated.

In pemphigus erythematosus, the head and feet are usually affected.

Pemphigus vulgaris is the most extreme form of pemphigus and may cover much of the body where ordinary skin meets �â'¬Å"specialized�â'¬ï¿½ skin, including the mouth, nose, and genitals.

When pemphigus is left untreated, animals go lame, live in pain, and may succumb to infection and die.

Autoimmune disorders are often misunderstood when they appear in people and in animals. People with autoimmune disorders find their symptoms not only ignored, but exacerbated by the stress of being told they are "imagining it". With animals, the problem is compounded by the fact that cats and dogs can't explain how they feel or tell us where it hurts; they have to rely on the people around them to examine, interpret and treat their problems. Noticing when a cat is in pain is often difficult; figuring out where the pain comes from, without the assistance of a knowledgeable vet, is nearly impossible.

Like the veterinarians who maintained that our cat was suffering from multiple, ongoing spider bites, many vets may not be on the lookout for pemphigus disorders because they are relatively rare: approximately .03% of animals are thought to have a pemphigus disorder. Because of its rarity and mysterious origins, pemphigus may also be confused for cancer and lupus.

Pemphigus is typically treated with drugs that suppress the immune system. The mildest versions of pemphigus may be treated with topical corticosteroids, but the treatment of choice has been Prednisone (or Prednisone). Prednisone suppresses the immune system, stopping the body's attack on specialized skin.

A week after starting Prednisone, our grumpy cat was immediately transformed into his playful, rowdy self. He galloped around the house for the first time in months, chasing us from room to room. He jumped on our heads in the morning and took playful swipes at us from under the furniture. He ate heartily. The tail-twitching stopped, and Madison demanded petting and playing. Maybe I imagined it, but he seemed as relieved as we were.

But immunosuppressant drugs don't target just one part of the immune system; they suppress all immune reactions, so animals who take these drugs are more likely to suffer from infections. Prednisone, as noted before, also has side effects: animals (and people) experience vastly increased appetite, weight gain, thirst and lethargy.

After an initial recovery period, side effects appeared. At the end of the first week on Prednisone, Madison was sleepy and grouchy. He didn't seem to be in any pain, and his initial symptoms were gone, but they were replaced with a distinct moodiness and lack of energy that worried us. We called the vet again.

She suggested Cyclosporine: an anti-rejection drug taken used by organ transplant patients. Cyclosporine helps the body accept the new organ. It had been used successfully in treating pemphigus in pets, but was more expensive than Prednisone. We decided to try it.

When switching from Prednisone to Cyclosporine, cats have to be carefully monitored. Prednisone-related drugs cause a build up of fats in the liver which can lead to diabetes. Knowing this, we had changed Madison to a dietetic cat food. Cyclosporine's main side effect is appetite suppression. The combination of increased fats stored in the liver coupled with drug-induced anorexia can cause cats to starve to death in as little as three days. Now, Madison needed to eat a lot. We switched him back from the dietetic cat food to a high-quality, high-protein canned food, giving him all he wanted. He had a diabetes test and it came up negative. His lethargy and depression disappeared within two days of taking the Cyclosporine; his pemphigus symptoms disappeared.

Pemphigus is usually a lifelong ailment, so we expect to have Madison on some kind of medication forever. However, autoimmune function is still mysterious: illnesses can abate at any time on their own. Madison's been on medication for nearly four years now, without another flare-up. In all respects, he's a healthy animal. Every other day, he gets a tiny bit of medicine in a mouthful of canned tuna--his all-time favorite food.

Although this is an article about pemphigus, at least as important is getting the right diagnosis and the best treatment for your pet. Veterinarians have such specialized knowledge that it is impossible for laypeople to tell good vets from those who aren't completely au courant with modern diagnostics and treatments. Really great vets can do more than treat our pets: they can provide us with answers and information that helps us make the best decisions for our pets.

**This article was published in Atlantic Pets Magazine, but has never before appeared online.**