Granulomatous rhinitis with intracranial invasion caused by Prototheca wickerhamii in a cat

A 10-year-old cat presented with a 2-year history of nasal discharge, sneezing, and nasal planum swelling. Granulomatous rhinitis caused by Prototheca wickerhamii infection was diagnosed on the basis of histopathological and genotypic analyses of biopsy samples. Oral voriconazole was administered; however, it caused adverse effects and was discontinued. The lesion, initially localized to the nasal planum, progressively extended into the nasal cavities, destroying the cribriform plate and orbital bone and invading the orbit and olfactory bulb. Following local voriconazole injection into the lesion, neurological impairment associated with increased intracranial pressure was observed. Despite transient resolution of clinical signs after resumption of voriconazole administration via a gastrostomy tube, the cat died from disease progression 465 days after the initial visit.