Calcospherite-like bodies and caseous necrosis in tracheal mucus from a dog with tuberculosis

A 3-year-old Wirehaired Fox Terrier was presented to the University Veterinary Hospital, University College Dublin, for evaluation of chronic cough of 8-months duration. Bronchoscopy showed a severely dilated collapsed left principal bronchus filled with highly viscous white mucus. Cytologically, globular lipid-like material and round concentrically laminated crystalline structures were evident within the proteinaceous mucus. These findings resembled the calcospherites and granular caseous debris often observed in human tuberculous patients. A Ziehl-Neelsen-stained cytocentrifuged preparation of material obtained by bronchoalveolar lavage revealed a few acid-fast rods within macrophages, suggestive of tuberculosis. At necropsy, granulomas with caseous necrosis were present in the lung parenchyma, bronchial and mediastinal lymph nodes, liver, pancreas, and mesentery. Granulomas were adherent to both kidney capsules and to the diaphragm. Histologically, there was evidence of mild calcification within caseous granulomas, which was confirmed by von Kossa's stain. Using Ziehl-Neelsen stain, acid-fast rods were identified within granulomas; bacterial culture was positive for Mycobacterium bovis. The cytologic findings in this case have not been reported previously in dogs and demonstrate a possible correlation between tuberculosis and calcospherite-like bodies with caseous, globular material in bronchial mucus, similar to that described in human patients.