Pepper, a 3 yo FS DSH, presents to you on a busy Friday afternoon for a recent history of skin irritation and licking. Pepper is an indoor/outdoor cat, and she is up-to-date on FVRCP, Rabies, and FeLV vaccines.
Not much is known about Pepper’s medical history; she was adopted from an animal shelter approximately six months earlier after being found as a stray. Pepper’s owner reports that she tries to give Revolution® monthly, though she occasionally forgets to give it. Her last dose of Revolution was administered “a little over a month ago.”
Pepper is a friendly, affectionate cat. Her BCS is 5/9, her mucous membranes are pink and moist, her capillary refill time is < 2 seconds, and she is bright, alert, and responsive.
You begin with an oral exam, noting that she has minimal tartar. However, you also notice some swelling and ulceration of her upper lip.
You point this swelling and ulceration out to the owner. She has not previously noticed this lesion and hasn’t seen Pepper acting as though her mouth is uncomfortable.
As you continue your exam, you do not find any abnormalities on thoracic auscultation or on abdominal palpation. You check her skin closely and comb her for fleas, but you don’t see any evidence of fleas or flea dirt on your exam.
However, when you roll Pepper onto her back to examine the skin on her ventral abdomen, you observe the following lesions on the medial aspect of the left hindlimb:
Similar lesions are also observed on the right medial hindlimb. You also note that Pepper’s popliteal lymph nodes are enlarged bilaterally.
What is your top differential?
Based on the appearance of Pepper’s skin (both the hindlimb lesions and the lip lesion), you should be thinking about feline eosinophilic granuloma complex (ECG).
Other differentials could include bacterial pyoderma, fungal infection, trauma, FeLV or FIV-associated skin lesions, or neoplasia.
What do you recommend for this patient?
The gold standard for the diagnosis of ECG is histopathology. This will allow ECG to be distinguished, with certainty, from other differentials. Reversible sedation combined with a local block is often sufficient to obtain a diagnostic punch biopsy.
If an owner is unwilling or unable to pursue histopath, there are other tests that can be used to support a diagnosis. Many ECG cats have hypereosinophilia on a complete blood cell count (CBC). Additionally, consider an impression smear or fine needle aspirate (FNA) of the lesions. You are likely to see large amounts of eosinophils if the lesion is an ECG, although it’s important to note that this is a relatively non-specific finding. Although a CBC and FNA cannot definitely diagnose ECG, they can provide a strong enough suggestion of the disease to move forward with treatment.
If this cat does have ECG, how will you treat it?
Immediate treatment of ECG relies upon steroids. Historically, veterinarians administered a long-acting steroid injection, like Depo-Medrol®. While this is effective and convenient for the owner, these injections are often associated with the development of diabetes mellitus. Therefore, oral prednisolone (1-2 mg/kg q12hrs, then taper) is now preferred.
Other drugs have also been utilized for the treatment of ECG in an effort to avoid or minimize the use of steroids. Essential fatty acids, cyclosporine, and antihistamines may play a role in treatment.
Finally, parasite prevention is essential in cats with a history of ECG. Both flea allergies and mosquito bite sensitivity are thought to play a role in the development of this condition. Cats with a history of ECG should remain on flea prevention year-round with consistent dosing. Additionally, cats should be kept indoors at all times, if possible. If owners are unwilling or unable to keep their cats indoors, they should at least bring them inside at dawn and dusk when mosquitoes are most active.
If appropriate parasite control does not prevent the recurrence of ECG, consider a workup for food allergy or atopy.