Eosinophilic Uveitis in Cats

Eosinophilic Uveitis Case Study

• An 8-year-old spayed domestic shorthaired cat was examined for recurrent anterior uveitis lasting 5 months.
• The cat also had a 4-year history of allergic or immune-mediated skin disease, managed with corticosteroids and cyclosporine.
• Frequent topical anti-inflammatory drugs controlled intraocular inflammation, but uveitis would relapse when therapy stopped.
• Secondary glaucoma developed, and the eye was enucleated.
• A complete blood count showed mild eosinophilia at the time of surgery.
• Histopathology revealed panuveitis with mixed inflammatory cells, predominantly eosinophilic, in the anterior chamber, iris, ciliary body, and choroid.
• No etiologic agents or malignancy criteria were found.
• The chronic dermatitis appeared in remission nine months after enucleation without further treatment.
• This is the first reported case of primarily eosinophilic uveitis in a cat with chronic allergic skin disease, possibly an ocular variant of feline eosinophilic granuloma complex.

Introduction

• Feline uveitis is a common condition with infectious, neoplastic, traumatic, or secondary causes.
• Systemic workups are done when no clear cause is found, including PCR screening, radiographs, or cytology.
• Etiology remains unknown in 40%-70% of cases, leading to a diagnosis of idiopathic or immune-mediated uveitis.
• Eosinophilic keratoconjunctivitis (EK) is an immune-mediated ocular surface disease in cats, possibly triggered by feline herpesvirus-1 (FHV-1).
• EK is diagnosed by identifying eosinophils on corneal or conjunctival cytology and treated with immunomodulatory therapy, antivirals, or antimicrobials.
• Eosinophilic inflammation can occur with feline systemic disorders like asthma, inflammatory bowel disease, parasitism, or dermatitis.
• Immune triggers include allergens or FHV-1, but the underlying cause isn't always found.
• Presumptive diagnosis of immune-mediated disease is made by therapeutic response to corticosteroids or immunomodulatory agents.
• This case report details a cat with eosinophilic panuveitis diagnosed by histopathology.
• This stands as the first known report of a predominantly eosinophilic uveal infiltrate causing uveitis in a cat.
• The cat had a history of allergic skin disease, suggesting the ocular signs relate to chronic dermatitis and indicating an atypical feline eosinophilic granuloma complex.

History and Examination

• An 8-year-old spayed, indoor cat was presented to the Ohio State University Veterinary Medical Center (OSUVMC) with a history of recurrent uveitis in the right eye (OD).
• Five months prior, the owner noticed cloudiness in the right eye.
• Initial diagnosis of anterior uveitis by the primary veterinarian, followed by a systemic workup with blood panel failing to identify an underlying cause.
• The cat was prescribed Neomycin-Polymyxin B Sulfate-Dexamethasone (NPD) ophthalmic ointment, clinical signs resolved, and medication was discontinued after a few weeks.
• A second episode occurred and the NPD was briefly resumed but relapsed two months later, leading to referral to OSUVMC ophthalmology service.
• The owner reported a history of dermatitis with facial pruritis and excessive grooming of the abdomen, with dermatologic signs appearing 4 years prior.
• The cat was treated with systemic antibiotics, methylprednisolone injections, food trial, and parasite control.
• Oral cyclosporine controlled skin disease but was tapered and discontinued just before the uveitis episodes.
• The physical examination was normal.
• Ophthalmic examination found mild blepharospasm and an absent menace response in the right eye.
• Dazzle and palpebral reflexes were positive in both eyes.
• The pupil in OD was not visible due to anterior chamber (AC) opacities, but pupillary light reflexes were present in the left eye (OS).
• Tonometry readings were 19 mm Hg in both eyes.
• Fluorescein stain was negative in both eyes.
• There was slight conjunctival hyperemia in the right eye with ~1–2 mm active perilimbal corneal vessels.
• White fibrinous material filled the AC, obscuring the iris.
• Aqueous flare (1+) and rubeosis iridis were identified but no deeper intraocular structures visible.
• The left eye was normal on the examination.
• Aqueocentesis and fluid analysis was declined by the owner.
• Differential diagnoses included neoplasia, infectious, parasitic or idiopathic disease.

Medical Management

• Prednisolone acetate 1% ophthalmic suspension was prescribed q 6 h until reassessment in 2 weeks.
• The next examination found a positive menace response and the AC had cleared enough to observe a normal ocular fundus.
• Fibrin was consolidated along the corneal endothelial surface, posterior synechiae, vascular membranes traversed the anterior lens capsule, and multifocal incipient anterior cortical cataract was present.
• Medical management continued by tapering the prednisolone acetate and adding diclofenac 0.1% ophthalmic solution.
• The owner reported a quiet eye with a focal coagulum of fibrin.
• Rescheduled visit due to travel plans and the cat was not medicated.
• At the next examination, the eye had worsened, with no menace response OD, tonometry showed 37 mm Hg OD and 13 mm Hg OS.
• Periocular erythema, swelling, and crusting of the upper eyelid skin OD.
• The globe was slightly buphthalmic with conjunctival hyperemia, perilimbal corneal blood vessels, and a superficial corneal ulcer. Fibrin and debris adhered to the posterior corneal surface and filled most of the AC, obscuring the pupil, lens, and ocular fundus.
• Due to the recurrence of uveitis, development of secondary glaucoma, and corneal ulceration, enucleation was discussed.
• The cat was discharged with oral prednisolone, topical antibiotic (ofloxacin 0.3% solution), topical glaucoma therapy (dorzolamide 2% solution), and topical diclofenac 0.1% solution.
• Enucleation was scheduled.
• Prior to general anesthesia, a complete blood panel (CBC, serum biochemistry) was repeated, which only revealed a moderate eosinophilia (26% eosinophils).
• A transpalpebral enucleation was performed without complications.
• The cat was discharged with oral antibiotics (amoxicillin-clavulanate) and a tapered dose of oral prednisolone.

Histopathological findings

• The globe was submitted to the OSUCVM anatomic pathology service in 10% buffered formalin.
• Routine histology was performed, and 4-µm sections were stained with hematoxylin and eosin (H&E) stain.
• Histologically, the AC was filled with eosinophilic amorphous debris.
• Intact inflammatory cells were observed at the periphery of this accumulation of debris, particularly close to the corneal endothelium, the iridocorneal angle, and the anterior aspect of the iris leaflet.
• The iris stroma was infiltrated and expanded by mixed inflammatory cells comprised of eosinophils, lymphocytes, plasma cells, and macrophages.
• A similar inflammatory cell infiltrate was also present in the AC, ciliary body, and choroid.
• Eosinophils were the predominant inflammatory cell type in all locations, comprising over 90% of the inflammatory cell population.
• Other findings included mild superficial corneal stromal neovascularization, cataractous change characterized by Morgagnian globule formation, and mild peripheral retinal atrophy with mild ganglion cell loss.
• No etiologic agents were observed, and neoplasia was not observed. The underlying cause for the uveitis was not apparent on histologic examination.

Follow-up/outcome

• The cat had no further clinical signs until 3 months after enucleation, when the owners noticed crusting, erythema, and mild pruritis of the skin dorsal and nasal to the healed surgical incision.
• No treatment was given.
• Six months after the enucleation, a consultation with the OSUCVM dermatology service found the facial lesions had healed.
• The cat had focal hypotrichosis and mild diffuse scaling, but no overt signs of allergic skin disease.
• A CBC was repeated, and the eosinophilia had resolved.
• A feline heartworm antibody test was negative.
• There were no ocular or dermatologic abnormalities noted nine months after enucleation OD, and the cat remains unmedicated.

Discussion

• Eosinophils are usually associated with immune-mediated or allergic disease, insect bite hypersensitivity, or parasites but have not been described as a predominant finding in anterior uveitis in cats.
• Histopathologic findings showed marked intraocular inflammation with eosinophils as the principal cell type, without evidence of infectious or parasitic agents.
• Led to a suspicion that the conditions may be linked in combination with the cat's past dermatitis history.
• Suggestive locations and immunomodulatory response of allergic or eosinophilic dermatitis, though there was no skin biopsy or cytology,
• The eosinophilic panuveitis may have been an ocular variant of feline eosinophilic granuloma complex, with the concurrent eosinophilia found on CBC potentially supporting this diagnosis.
• Feline eosinophilic granuloma complex is a group of distinct lesions with similar histologic findings that often affect the face, upper lip, footpads, or ventral abdomen, but can appear anywhere on the body.
• The underlying cause of these predominantly eosinophilic skin conditions includes hypersensitivity to environmental or food allergens, insect bites, or secondary infection with FHV-1.
• The patient did not have allergen testing during her initial dermatitis workup, but was treated for internal and external parasites.
• The cat was also placed on a prescription diet (Hill's Science Diet feline c/d; Hill's Pet Nutrition, Inc., Topeka, KS, USA).
• Aqueocentesis was offered to obtain aqueous humor (AH) for cytology and to submit for PCR viral testing, although it is rarely helpful in reaching a diagnosis in cats with uveitis.
• The abundance of eosinophils in the AH of this patient may have altered the course of therapy as mast cells in the AH of mast cell tumor dogs has been reported.
• The current patient did not have any neoplastic characteristics found on histopathology, and mast cells were not described in the sections examined.
• With the history of skin disease and recent discontinuation of oral CsA, the revelation of a marked eosinophilic uveitis may have prompted more aggressive systemic treatment with immunomodulatory drugs.
• A blood eosinophil count >1.5 × 10º/L can be seen with flea allergy, gastrointestinal disease, asthma, eosinophilic granulomas, or as an idiopathic finding
• The patient in this report had a mild eosinophilia which resolved 6 months after enucleation with no changes to her environment, diet, or parasite control
• A negative heartworm test ruled out this cause for eosinophilia and uveitis.
• therapeutic response is used to diagnose immune-mediated or allergic disease when extensive diagnostic testing is not feasible.
• Therapeutic response is used to diagnose immune-mediated or allergic disease when extensive diagnostic testing is not feasible.
• The patient's dose of CsA was unknown, but was reported by the owner to have been progressively decreased over several years.
• It may be that the eosinophilic uveitis was a breakthrough inflammatory event, potentially triggered by exogenous factors as the immunomodulatory drug was tapered.
• This case report describes a previously unreported eosinophilic uveitis in a cat with a concurrent history of dermatitis.
• The uveitis was responsive to anti-inflammatory therapy, but relapsed when medication was discontinued.
• The eosinophilic infiltrate led to secondary glaucoma OD.
• Four months after enucleation and discontinuation of all medications, there was a brief relapse of facial dermatitis that resolved with no treatment.
• The owners plan to closely monitor the cat for both ocular and skin disease and will consider resuming immunomodulatory therapy if indicated.