Clinical and clinicopathologic features of an undifferentiated resolving uveitis in kittens similar to that seen with feline infectious peritonitis.

OBJECTIVE

To highlight clinical and clinicopathologic differences between kittens with feline infectious peritonitis-associated uveitis (FIP-AU) versus those with an otherwise similar feline undifferentiated resolving uveitis (FURU).

METHODS

Clinical and clinicopathologic data were compared between 22 kittens with FURU and 8 with necropsy-confirmed FIP-AU examined between January 1, 1985, and December 31, 2022.

RESULTS

Sex, lifestyle, seasonality, household cat numbers and systemic signs were similar in both groups. Feline undifferentiated resolving uveitis occurred predominantly in domestic-breed kittens from shelters, whereas FIP-AU was more frequent in purebred or stray cats. Duration of ocular signs before presentation was 1 to 2 weeks for FURU versus > 2 months for FIP-AU. Feline undifferentiated resolving uveitis was more commonly associated with episcleral hyperemia while FIP-AU was more commonly associated with corneal edema, dyscoria, rubeosis iridis, iridal congestion/thickening, posterior synechia, or keratic precipitates. Corneal edema and chemosis were more severe in FIP-AU. No eyes with FURU had fundic abnormalities whereas 6 of 11 eyes with FIP-AU had chorioretinitis. All kittens with FIP-AU presented bilaterally whereas 5 of 15 kittens in which FURU was ultimately bilateral, initially presented unilaterally. Hyperproteinemia, hyperglobulinemia, and hyperbilirubinemia occurred only with FIP-AU. Neither likelihood of a positive coronavirus titer nor titer magnitude differed between groups.

CONCLUSIONS

Kittens can develop bilateral fibrinous uveitis with keratic precipitates, systemic signs of illness, and serum coronavirus antibodies which resolves without sequelae following empirical treatment. Syndromic assessment-including careful fundic examination-can help differentiate FURU from FIP-AU and should precede antiviral therapy.

CLINICAL RELEVANCE: Resolution of uveitis during antiviral treatment does not confirm FIP. Comprehensive diagnostic evaluation is essential to avoid misdiagnosis and inappropriate treatment.