Pulmonary cryptococcosis with an endobronchial cryptococcoma in a Warmblood mare

This report describes pulmonary cryptococcosis with a large endobronchial cryptococcoma in an 8-year-old Warmblood mare. The mare was presented initially with fever and lethargy, and clinical signs typical of bacterial pneumonia. Markedly elevated serum amyloid A (SAA) concentrations indicated a severe systemic inflammatory response. Over a period of 6 wk, the condition progressively worsened and was refractory to multiple courses of broad-spectrum antimicrobial therapy as administered in a field setting. Diagnostic imaging following referral revealed extensive consolidation of the left lung and multiple nodular lesions. Endoscopy identified a large granulomatous mass nearly completely occluding the left mainstem bronchus. Histopathologic examination of biopsy samples from the mass and lung parenchyma revealed a severe pyogranulomatous inflammation composed of numerous encapsulated, budding yeast organisms (8.5 to 12.5 μm in diameter with a 2- to 3-μm thick capsule) morphologically pathognomonic for Cryptococcus spp. Due to extensive, irreversible lung damage and poor prognosis, euthanasia was elected. Key clinical message: This case serves as a reminder to include fungal pathogens such as Cryptococcus in the differential diagnosis of severe and non-responsive pneumonia in horses.