Fungal Clues in Feline and Canine Snoots: CT Scans Unmask Cryptococcus!

CT findings of nasal cryptococcosis in cats and dogs: A case series

Cooley S, Galustanian G, Moon A, Summers S

Background
Cryptococcosis, a fungal infection caused primarily by Cryptococcus neoformans and C. gattii, affects the nasal cavity and associated structures in dogs and cats. While CT is often used to assess chronic rhinitis and plan treatment, detailed descriptions of CT findings specific to nasal cryptococcosis are limited. This study aimed to describe CT characteristics of nasal and nasopharyngeal lesions in confirmed cases of cryptococcosis in cats and dogs.

Methods
This retrospective, single-center case series included 10 cats and 12 dogs diagnosed with nasal cryptococcosis between 2010 and 2020 at Oregon State University. Diagnosis was confirmed via cytology, histopathology, or serology. CT scans of the head were evaluated for nasal/nasopharyngeal masses, bone lysis, cribriform plate involvement, intracranial extension, and lymphadenopathy. A board-certified veterinary radiologist reviewed all images.

Results
In cats, 80% had nasal lesions (mostly non-destructive rhinitis) and all had nasopharyngeal masses, typically located caudally. Only 30% had a nasal mass, and none had cribriform plate lysis or intracranial involvement. In contrast, all dogs had nasal lesions, 92% exhibited destructive rhinitis, and 67% had a nasal mass—most of which extended into the nasopharynx. Cribriform plate lysis was observed in 75% of dogs, and 33% had intracranial mass extension. Lymphadenopathy was variable in both species. Middle ear involvement was present in 60% of cats but not in dogs.

Limitations
The study was limited by its retrospective nature, small sample size, and potential selection bias toward more severe or complex cases that warranted advanced imaging. CT interpretation was performed by a single unblinded radiologist, and the cryptococcal species/molecular type was not identified in all cases. Thus, findings may not generalize to all forms of nasal cryptococcosis.

Conclusions
CT findings suggest species-specific patterns of nasal cryptococcosis: cats commonly have nondestructive rhinitis with caudal nasopharyngeal masses, while dogs typically present with destructive nasal disease, nasal masses, cribriform plate lysis, and occasional intracranial extension. These differences support the inclusion of cryptococcosis in differential diagnoses for nasal and nasopharyngeal masses in both species. Advanced imaging, combined with confirmatory diagnostics, remains essential for accurate diagnosis and management.

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