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Pemphigus. It’s a horrible sounding word
that most cat owners have probably never heard. Barnee Escott, however,
was introduced to the word at her veterinarian’s office a few months
ago, and she’d be happy if she – and her cat Oliver – never hear it
again.
Oliver was a rescue cat, adopted by Escott from a local sanctuary.
Everything about Oliver was pretty darn cute, except the thick grey
scaly patches on both of his ears. At his first post-adoption veterinary
visit, ringworm – a common skin fungus – was suspected as the cause of
his ear condition, and a fungal culture confirmed the diagnosis.
Treatment of the ringworm was successful, but the ear lesions never
fully resolved. In fact, new scaly patches were cropping up - on his
feet! The distribution pattern of Oliver’s skin lesions lit a light bulb
over his vet’s head: perhaps we were dealing with an auto-immune skin
disorder.
Auto-immune disorders are those in which an animal’s immune system
mounts an attack against itself. The pemphigus group of diseases is a
set of auto-immune skin diseases that cause blisters and erosions of the
skin, as a result of the immune system mistakenly regarding the cells in
the skin as being foreign, and attacking them. The pemphigus diseases
are the most common auto-immune skin diseases recognized in cats and
dogs. One particular disorder, pemphigus foliaceus (pronounced pem-fig-us
fō-lee-ā-shus, and abbreviated PF in this article), is the more common
of these feline skin disorders.
There is no age or breed predilection for PF in cats. One report showed
the median age of onset to be 5 years, although it has been reported in
cats as young as 1 and as old as 17. There is also no sex predilection –
males and females are equally affected.
The head is the most commonly affected area. Cats with PF often show
signs of the disorder on the ears, nose, chin, and around the eyes. The
lesions tend to be bilaterally symmetrical, i.e. whatever is present on
the one side of the head tends to also be present in mirror image on the
other side, more or less. The footpads, nail beds, and area around the
nipples are also commonly affected. Foot involvement is common, with
multiple toes and multiple feet affected. In some cases, systemic signs
of illness may be present, including fever, lethargy, weight loss, poor
appetite, and enlarged lymph nodes. Cats with foot involvement may also
show lameness.
The lesions caused by PF can resemble those of other diseases, including
ringworm, bacterial skin infections, parasitic skin infections, inhalant
allergies, and food allergies. Various tests, such as a skin scraping
and fungal culture may be necessary to rule out parasitic and fungal
infections. To obtain a definitive diagnosis of PF, skin biopsy
specimens are required. The best specimens are those areas of skin that
contain an intact pustule, however, these are hard to find, as pustules
rupture easily. On occasion, a preliminary diagnosis may be made by the
veterinarian via cytology. For example, if an intact pustule is present,
it may be possible to puncture the pustule, collect the contents, and
evaluate it on a microscope slide. The presence of a particular type of
cell, called acanthocytes, is highly suggestive of the disorder. This
preliminary diagnosis should be confirmed, however, by biopsy. This test
also helps rule out other pustular skin diseases, like pyoderma
(bacterial infection of the skin). Submitting multiple biopsies
increases the chances of obtaining diagnostic sample. It is important
that the biopsy specimen be evaluated by a pathologist with particular
expertise in skin disorders. Oliver’s vet performed biopsies on the
affected areas of Oliver’s skin, and as you’ve probably figured out by
now, pemphigus foliaceus was the final diagnosis.
“My initial reaction was shock”, said Escott. “I have had cats for 40
years and never even heard of pemphigus!” But she was undaunted. “I
decided I wanted to give him the best quality of life that I could, for
as long as possible”, she said.
Treatment of PF usually involves administration of oral corticosteroids.
Initially, high doses are used to get the disorder under control, and
then the dose is gradually tapered, with the goal being the lowest
possible alternate-day dosage that controls the clinical signs. Oliver
was treated with prednisone, a commonly prescribed corticosteroid.
Potential side effects of corticosteroids include excessive thirst and
urination, increased appetite, weight gain, and increased risk of
infection. Prolonged use can predispose some cats to developing
diabetes. Fortunately, cats are fairly resistant to the adverse effects
of steroids, especially when compared with dogs.
If steroids alone fail to produce remission, or if unacceptable side
effects occur, alternative or concurrent medications can be
administered. Chlorambucil, a chemotherapy drug, is a good second drug
to try if steroids alone produce inadequate results. In fact, some
veterinarians initially treat with both drugs, and then taper the drugs
so that the cat is maintained on alternating day therapy, with steroids
given one day, and chlorambucil given the other day. In some instances,
the steroids can be completely discontinued and the disease kept under
control on chlorambucil alone. Another drug that can be tried are gold
salts. They are available orally, or as an injection. The injectible
form is thought to be more effective, although the drug is expensive and
can be difficult to obtain. Injections are usually given weekly until
remission occurs (usually 6 to 12 weeks), and then decreased to every
two weeks, and then every one to two months.
Oliver responded well to high doses of corticosteroids, but when tapered
to every other day therapy, his skin flared up again. His steroid dosage
was increased; the PF went back into remission, and chlorambucil was
administered concurrently. After two months, Escott was able to reduce
the prednisone and chlorambucil. It’s been three years since Oliver’s
diagnosis, and he continues to do well, despite the subsequent
development of lymphocytic plasmacytic gingivitis/stomatitis, a painful
mouth condition (see my article “Oral Agony” in the July 2006 issue of
Catnip for more details about this disorder). When his mouth flares up,
it becomes difficult to medicate him orally, and some of his medications
are given by injection instead. This protocol seems to be working quite
well, and Oliver shows no signs of slowing down.
Updated
7/2/07 |
