Sinonasal Nocardia farcinica in a cat with comorbidities.

A 15-year-old spayed female domestic shorthair cat was referred because of a chronic history of swelling over the right eye that had progressed to an open, exudative wound. The lesion had not responded to prolonged antimicrobial treatments that were chosen based on superficial culture results. Before this development, the cat had been diagnosed with International Renal Interest Society (IRIS) stage 2 chronic kidney disease with no other significant health issues. Computed tomography revealed fluid to soft-tissue attenuating material in the sinonasal cavities and concurrent bony lysis. Cytology and biopsy of the frontal sinus cavity were suggestive of nocardiosis, which culture confirmed as Nocardia farcinica. Treatment using sulfonamide antibiotics was instituted and resulted in resolution of the clinical signs but did not provide a cure. The cat spontaneously died 1 y following the start of therapy due to causes unrelated to the N. farcinica infection, as confirmed by necropsy. Key clinical message: Nocardia spp. sinonasal infections are rare in small-animal patients but should be considered in cases of rhinosinusitis not responsive to empirical therapy. This report details management of a case of sinonasal nocardiosis in a cat with comorbidities.