It is imperative to start with a complete and detailed patient history. The history should include where and when the lesions first started, whether or not the cat is pruritic, a thorough medication history of both long-term and newly administered medications, any progression or changes in the clinical signs, and any observations about the cat's systemic health (e.g. drinking and urination habits, appetite, weight loss, activity).
It is also important to remember that even though more aggressive diagnostics may be indicated in an older feline patient, common diseases still occur commonly in older cats. For example, even an older cat can develop lesions secondary to flea hypersensitivity if there is a break in the administration of flea control products or a change in the cat's environment. Routine monthly flea preventive is recommended for all cats, regardless of their age.
Regardless of the initial presenting complaint, it is important to start the diagnostic investigation with these core dermatologic tests:
A dermatophyte culture is often warranted as a first-line diagnostic test in feline patients, especially if a cat is deemed to be at risk (e.g. indoor-outdoor lifestyle, new cat added to the household, interaction with other cats). Most of these tests can be performed during the initial examination. The results of these core diagnostics will directly affect treatment or recommendations for additional diagnostics.1
Unkempt hair coat
An unkempt hair coat is a generalized clinical sign that typically indicates a cat is not grooming itself as it normally would. It can be characterized by increased oiliness, matting or adhered tufts of hair, scales, odor, fecal or urine contamination of the coat, exudate accumulation, evidence of bacterial or yeast overgrowth on the skin, or paronychia.2
Core diagnostic tests are certainly indicated to rule out parasites as well as to determine if bacterial or yeast infections are the primary cause or are complicating a definitive diagnosis. A complete blood count, serum chemistry profile, and urinalysis are indicated as first-line diagnostics to begin to rule in or rule out an endocrine or metabolic disorder (e.g. hyperthyroidism, hyperadrenocorticism, diabetes mellitus, renal disease).
Examination of the oral cavity and palpation of the thyroid gland can also help to make a complete differential diagnosis list. If the patient seems to be in pain or has mobility, joint, or gait abnormalities, a radiographic examination to check for arthritic or other bony changes should be considered.
It is important to discuss pain management strategies with the owner. This is not only in the form of medications but also can entail environmental changes, such as making sure that litter boxes are accessible and that the boxes do not have high walls or small openings where an arthritic cat would have trouble maneuvering.
Scale refers to flakes of keratin that break off from the cornified layer of the epidermis. Scaling as a new clinical sign should prompt a thorough investigation using core diagnostic tests.2 Dermatophytosis should also be ruled in or ruled out based on the results of a trichogram, Wood's lamp examination, and fungal culture. It is important to ask the owner whether any animals have been added to the household as well as about the use of flea control products. Deep and superficial skin scrapings are useful in determining whether Cheyletiella or Notoedres species infections are causes of scale. A fecal examination can also be helpful if certain contagious mites (i.e. Demodex gatoi) are suspected.3
Primary skin neoplasia (epitheliotrophic T cell lymphoma) or paraneoplastic exfoliative dermatitis can also present as excessive scaling with varying levels of pruritus (Figure 2). Scales are often large and broad, sometimes exfoliating in sheets. Other possibilities include drug eruption, erythema multiforme, and sebaceous adenitis. Skin biopsy can be diagnostic; however, because paraneoplastic exfoliative dermatitis is associated with thymoma, full blood work and thoracic radiographs are recommended if the skin biopsy comes back as consistent with paraneoplastic dermatitis or if biopsy results are nonspecific. Surgical removal of the thymoma can be curative in these cases.5,6
The treatment of and prognosis for diseases associated with scaling are quite variable, so determining a definitive diagnosis is important to be able to have an informative conversation with the owner.
Thin, fragile skin
Cutaneous asthenia is another cause of fragile, easily torn skin, but it is a congenital disease of collagen or elastin and typically shows up in very young cats. However, severe metabolic disorders could exacerbate a subclinical case of cutaneous asthenia, causing the new clinical sign of hyperfragility in an older cat.8,9
Fragile skin syndrome is often diagnosed based on clinical signs alone, since the presenting signs are pathognomonic for the disorder. The search for the underlying cause includes a complete blood count, a serum chemistry profile, a urinalysis, and specific tests such as an ACTH stimulation test, a low-dose dexamethasone suppression test, or abdominal ultrasonography. Skin biopsies show marked dermal and epidermal atrophy. It is difficult, however, to perform a skin biopsy on these patients because skin can tear and the dermis may easily separate from the underlying adipose tissue.10
Without any underlying disease to treat, these patients can be difficult to manage. The skin wounds can be sutured, but skin will continue to tear easily unless the primary disease is identified and treated.
Alopecia can happen for numerous reasons. It is important to first establish if the alopecia is self-induced or spontaneous, which can be determined by performing a trichogram and observing the hair shaft integrity. The source of the alopecia can also be investigated by placing an Elizabethan collar on the patient and seeing if hair loss continues while the cat is restricted from grooming.
The location of the alopecia can help narrow down the list of differential diagnoses. For example, caudal ventral abdominal alopecia can be secondary to infection (bacteria, fungi, parasites) or allergies but could also be caused by urinary tract pain or other abdominal pain.
These patients often do not feel well, with concurrent weight loss and gastrointestinal signs. Skin biopsy can certainly help with a diagnosis, but thoracic and abdominal radiography or abdominal ultrasonography is more likely to find the causative neoplasia. If it is possible to remove the tumor or treat the cancer, hair can regrow.
Alopecia areata and pseudopelade are two rarer conditions that can cause alopecia. Both conditions cause a grossly noninflammatory, nonpruritic alopecia. In alopecia areata, lymphocytes invade the bulb of the anagen hairs, causing a patchy alopecia; in pseudopelade, the lymphocytic inflammation is within the isthmus, causing a diffuse alopecia.5
Other causes of alopecia in a geriatric cat include a cutaneous drug reaction, an endocrinopathy (especially hyperadrenocorticism), anagen/telogen defluxion, sebaceous adenitis, or an injection reaction. A skin biopsy is the most important diagnostic tool to help differentiate among the possible causes of alopecia in an older feline patient.
There are three general categories for any patient presenting with pruritus as the primary clinical sign—parasites, bacterial or fungal infection, and allergy. However, if the pruritus is a new clinical sign in an older cat, these broad categories can be narrowed down quickly. As has been previously stated, parasites can affect an animal at any age. Bacterial or fungal infection can also affect an animal of any age. In fact, geriatric patients are often predisposed to these conditions because of their age, especially if a patient has any other systemic diseases affecting the immune system.
It is especially important to look for evidence of demodicosis. Finding Demodex cati mites warrants a more thorough medical workup for a systemic disease predisposing the cat to unchecked mite proliferation.
If infection and parasites are ruled out and a feline patient remains pruritic, food allergy should be considered. It is unlikely that an older cat would develop environmental allergies, resulting in late-onset pruritus. A strict dietary trial with a home-cooked novel protein or a hydrolyzed protein commercial food should be performed. However, care should be taken to ensure that there are no other medical causes that need to be considered when designing the diet trial.11
Unilateral otitis externa or otitis media
Unilateral otitis externa or otitis media in an elderly cat with no history of ear disease is most likely secondary to an aural mass. An aggressive workup should be instituted at the initial examination. Perform an otoscopic examination to look for any abnormal tissue in the ear canal. This may need to be done under sedation if the cat is experiencing any pain or discomfort. The workup should include a complete blood count, a serum chemistry profile, a urinalysis, and imaging of the skull or bullae, ideally via computed tomography, but radiography or magnetic resonance imaging are other possibilities.
Often the treatment of choice is surgery to remove the ear canal. In certain cases, if the neoplasia is not aggressively invading surrounding soft tissue or the bone of the middle or inner ear or skull, surgery can be curative and provide a great deal of comfort to the cat.12
Geriatric cats that are presented for evaluation of skin or coat changes can be a diagnostic challenge. Remembering to collect an appropriate history and perform core dermatologic tests will provide a solid basis on which to recommend further testing or treatment.
Darcie Kunder, VMD
Matthew J. Ryan Veterinary Hospital
University of Pennsylvania
Philadelphia, PA 19104
Karen A. Moriello, DVM, DACVD
Department of Medical Sciences
School of Veterinary Medicine
University of Wisconsin-Madison
Madison, WI 53706
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