Multimodal treatment of recurrent sinonasal cryptococcal granulomas in a horse

A 7-year-old 509-kg (1,120-lb) Tennessee Walking Horse mare was evaluated because of bilateral mucosanguinous nasal discharge, intermittent right-sided epistaxis, and worsening dyspnea of 9 months' duration.

Multiple masses in the nasopharynx were detected via endoscopic and radiographic examinations. Cytologic and histologic examinations of biopsy specimens of 1 mass revealed round yeasts with thick nonstaining capsules and occasional narrow-based budding that resembled cryptococcal organisms.

Oral administration of fluconazole and organic ethylenediamine dihydriodide and intermittent intralesional injections with fluconazole, amphotericin B, and formalin resulted in resolution of lesions for a period of 2.5 years. The horse then developed exophthalmos, recurring clinical signs, and extensive nasopharyngeal masses. The masses were surgically debulked via a large frontonasal bone flap, and the horse was treated with IV injections of amphotericin B and long-term oral administration of fluconazole. Clinical signs did not recur in the following 2-year period. A presumptive diagnosis of cryptococcosis was made following cytologic and histologic evaluations of the masses; results of serologic analysis and fungal culture confirmed infection with Cryptococcus neoformans.

Cryptococcal infection of the upper respiratory tract in horses has previously been described as a uniformly fatal disease. As this case report illustrates, medical and surgical treatment of sinonasal cryptococcal granulomas in horses may be successful, but the importance of long-term follow-up and the potential for disease recrudescence should be considered. As efficacious antifungal agents become less expensive, their increased use will likely decrease mortality rates in horses with fungal infections.