Nothing is more heart warming than watching a patient grow in your practice from infancy to an aged pet. It is truly beautiful
to see a caring owner trying to do the best for their geriatric pet to enhance the quality of their remaining years. They
look to us for guidance and expertise to extend the quality time they have with that pet. Perhaps our role as veterinarians
is more of a prophylactic one, in that we try as the patients get older to "catch" an impending or early disease before it
has a chance to take hold. Hence the importance of a good physical exam and geriatric work up which includes education of
the client, blood work, and sometimes more extensive diagnostics. Thankfully in dermatology, pets do not seem to parallel
humans in their aging changes of the skin. However, certain symptoms which can be "red flags" for other diseases in the aged
patient should be identified. The emergence of recurrent pyoderma or demodicosis in a geriatric patient should clue us into
looking deeper for an underlying cause. Certain keratinization changes such as those seen in hepatocutaneous syndrome signal
us as veterinarians to look for underlying liver pathology including diabetes mellitus. And finally, neoplasia is certainly
more prevalent in the older patient, particularly cutaneous lymphoma.
Photo 1: Elderly Cocker Spaniel with generalized demodicosis secondary to underlying Cushing's disease.
Reading the signs
When an adult canine that has otherwise been healthy with no history of steroid use presents with generalized demodicosis,
a search for an underlying disease should be undertaken. One study indicated that 20 percent of generalized adult onset demodicosis
patients may have underlying Cushing's disease, 12 percent may be hypothyroid, 24 percent have underlying allergy, 15 percent
on chemotherapy, and 29 percent have an unidentified disease. Perhaps the most common breed of elderly patient that presents
with Cushing's disease in our practice is the Cocker Spaniel, followed by the Golden Retriever and Labrador Retriever (Photo
1). I have been known to say throughout the day that "an old Cocker Spaniel is Cushing's disease waiting to happen". Cushing's
disease is mentioned because in an elderly canine, many times the initial presentation is that of generalized demodicosis.
Skin scrapings, blood work, along with further diagnostics should be performed. Once demodex mites are found in skin scrapings,
we check a CBC/profile/urinalysis. If you see additional signs of Cushing's disease such as enlarged abdomen, thin skin, muscle
atrophy, visible abdominal skin vessels, or calcinosis cutis, an ACTH stimulation test or low dose dexamethasone suppression
test should be performed to confirm the diagnosis. Most often, liver enzymes are elevated on the serum profile in a patient
with Cushing's disease, but I have had an occasional patient (both Cocker Spaniels) where the liver enzymes were normal. I
also hear the comment that the liver enzymes "aren't up very much". An ACTH stimulation test should be performed if the liver
enzymes are in the least bit elevated assuming the patient has not been on any topical or systemic steroids, or other medications
that will cause liver enzyme elevations such as phenobarbital. We usually start with a one-hour ACTH stimulation test, if
the results confirm Cushing's disease, a referral is made to the internist for an abdominal ultrasound to rule out adrenal
tumor. If pituitary-dependent Cushing's disease is confirmed, Lysodren therapy is initiated. If the ACTH stimulation test
does not confirm Cushing's disease, a low dose dexamethasone suppression test should be performed or wait another eight weeks
and recheck the ACTH stimulation test. A elevated resting cortisol level is not diagnostic for Cushing's Disease. An elevated
resting cortisol level is merely a reflection of the patient's anxiety level. The real analysis is the one- or two-hour post
cortrosyn or ACTH cortisol level as it measures the body's response to a cortisol stimulus.
Photo 2: Shetland Sheepdog with adult onset demodicidosis. A bladder tumor was diagnosed one month later.
Underlying neoplasia or "impending" neoplasia should also be considered in a geriatric patient with generalized demodicosis.
If a search including blood work, radiographs and/or ultrasound does not yield a neoplasm, the patient should be monitored
closely in the future. In one of our patients, an elderly Shetland Sheepdog with generalized demodicosis, a bladder neoplasm
was detected a few months after the diagnosis of demodicosis (Photo 2). Not all geriatric patients with generalized demodicosis
will have underlying internal medicine issues, but since studies indicate a majority can, it is important to monitor particularly
for Cushing's disease, an existing neoplasm or an "impending" neoplasm by routine checkups.
Skin "lumps and bumps" are particularly important to check in elderly patients since neoplastic cells tend to pick on older
individuals. It is important to perform fine needle aspirates of any and all skin masses. It is tempting on a busy day to
just palpate skin masses and write them off as "lipomas" and "we'll just keep an eye on it". However the few extra minutes
it takes for the veterinarian or technician to perform the needle aspirate and read the slide in house or send it to the pathology
lab for analysis, may be well worthwhile. Certainly a fine needle aspirate is not a substitute for surgical removal and biopsy
but it may give an indication as to which way to proceed. Astute owners and groomers often will detect these skin masses and
if they feel they are important enough to point out, it is our responsibility to follow these with diagnostics. Lipomas, mast
cell tumors, histiocytomas, and focal lymphoma tumors are probably diagnosable in house but if there is any doubt as to the
type of cell or which way to proceed, a second opinion on the cytology should be obtained from the pathologist (Photo 3).
In house cytology requires very little time and you will become more proficient the more you do it. Cutaneous lymphoma was
discussed in previous articles but it should be remembered that clinically, those lesions can resemble bacterial pyoderma
(Photo 4). It is very important to perform skin biopsies on lesions that you feel are not responding normally to therapy.
Photo 3: Mast cell tumor on a Boxer.