Reactive histiocytosis of the orbit and posterior segment in a dog

Canine idiopathic orbital inflammation: A case series of four affected dogs (five orbits)

PURPOSE

In humans, idiopathic orbital inflammation (IOI) is a diagnosis attributed to benign, inflammatory orbital conditions without identifiable local or systemic cause. We describe the clinical signs, imaging and histopathological findings, management and outcome of four dogs diagnosed with IOI.

METHODS

Multicentric retrospective study.

RESULTS

A total of four dogs (five orbits) of three different breeds (three cases were English Springer Spaniels [ESS] or ESS-cross) and ages ranging from 3 to 12 years were included. Initial presenting signs were unilateral and included exophthalmos, enophthalmos, globe deviation, thickening and protrusion of the third eyelid and conjunctival hyperemia. Computed tomography and magnetic resonance imaging identified heterogeneous space-occupying, contrast-enhancing orbital lesions in all cases. Sparing of the retrobulbar space was detected in four of five orbits. Histopathology revealed mixed inflammatory infiltrates of lymphocytes, plasma cells, and histiocytes. Immunohistochemistry was performed in two cases highlighting the presence of histiocytes and lymphocytes, predominantly T cells. Resolution of clinical signs was achieved in two cases managed with oral immunosuppressant medication (corticosteroids alone or combined with cyclosporine or azathioprine), one went into spontaneous remission, one resolved with topical corticosteroids, and one underwent exenteration. Recurrence occurred in two cases within 15 months of initial diagnosis and required further immunosuppressant medication. One case developed signs in the contralateral orbit within 8 months of presentation.

CONCLUSIONS

IOI is an uncommon condition in dogs. Its diagnosis relies on the combination of advanced imaging and histology. As in humans, it appears that spontaneous remission and recurrence may occur requiring long-term immunosuppressant medication.

Unilateral eosinophilic cellulitis leading to implant extrusion after bilateral enucleation in a dog

A mixed breed dog underwent bilateral enucleation with orbital implant placement for secondary glaucoma. Subsequent unilateral implant extrusion occurred. An orbital mass histologically consistent with eosinophilic cellulitis was discovered. It may have developed secondary to communication between orbit and skin. Inflammatory processes mimicking neoplasia can cause implant loss post‐enucleation.

Prognostic Factors for Recovery of Vision in Canine Optic Neuritis of Unknown Etiology: 26 Dogs (2003-2018)

Optic neuritis (ON) is a recognized condition, yet factors influencing recovery of vision are currently unknown. The purpose of this study was to identify prognostic factors for recovery of vision in canine ON of unknown etiology. Clinical databases of three referral hospitals were searched for dogs with presumptive ON based on clinicopathologic, MRI/CT, and fundoscopic findings. Twenty-six dogs diagnosed with presumptive ON of unknown etiology, isolated (I-ON) and MUE-associated (MUE-ON), were included in the study. Their medical records were reviewed retrospectively, and the association of complete recovery of vision with signalment, clinicopathologic findings, and treatment was investigated. Datasets were tested for normality using the D'Agostino and Shapiro-Wilk tests. Individual datasets were compared using the Chi-squared test, Fisher's exact test, and the Mann-Whitney U-test. For multiple comparisons with parametric datasets, the one-way analysis of variance (ANOVA) was performed, and for non-parametric datasets, the Kruskal-Wallis test was performed to test for independence. For all data, averages are expressed as median with interquartile range and significance set at p < 0.05. Twenty-six dogs met the inclusion criteria. Median follow-up was 230 days (range 21–1901 days, mean 496 days). Six dogs (23%) achieved complete recovery and 20 dogs (77%) incomplete or no recovery of vision. The presence of a reactive pupillary light reflex (p = 0.013), the absence of fundoscopic lesions (p = 0.0006), a younger age (p = 0.038), and a lower cerebrospinal fluid (CSF) total nucleated cell count (TNCC) (p = 0.022) were statistically associated with complete recovery of vision. Dogs with I-ON were significantly younger (p = 0.046) and had lower CSF TNCC (p = 0.030) compared to the MUE-ON group. This study identified prognostic factors that may influence complete recovery of vision in dogs with ON. A larger cohort of dogs is required to determine whether these findings are robust and whether additional parameters aid accurate prognosis for recovery of vision in canine ON.

Histiocytic chorioretinitis in a dog

A 3-year-old castrated male mixed-breed dog presented with an acute bullous retinal detachment and thickened choroid of the right eye. Subretinal cytology revealed an atypical cell proliferation suggestive of neoplasia. The eye was enucleated, and the original diagnosis was a histologically benign choroidal melanocytic tumor. Further diagnostics revealed no other systemic abnormalities other than a nonhealing shoulder wound. Six months later, the left eye developed a bullous retinal detachment. This eye responded well to systemic steroids and the dog regained vision within a few weeks of initiating therapy. Results of immunohistochemistry with Melan-A and CD204 of the previously enucleated right eye caused a revision of the histologic diagnosis from melanocytic tumor to histiocytic chorioretinitis. This case highlights the subtle and sometimes confusing distinction between neoplastic and inflammatory processes on both cytology and histopathology.