Acid-fast bacilli associated with a conjunctivo-corneal mass in a cat

Purpose: To describe a case of conjunctivo-corneal mass in a cat that was characterized histopathologically by presence of acid-fast bacilli. Methods: a two-year-old female black european shorthair cat, living in a suburban environment, with an outdoor lifestyle, was presented for evaluation of a 2 weeks’ duration nodular pinkish vascularized mass arising in the dorsal bulbar conjunctiva at the temporal cantus of left eye and invading the lateral surface of sclera and cornea. No other abnormalities were seen on both eyes by slit-lamp biomicroscopic and indirect ophtalmoscopic examination. Serologically feline leukemia virus and feline immunodeficiency virus were excluded, but IgM title for toxoplasmosis was 1:640. Cytobrush samples were obtained and a biopsy of the mass was performed. Results: Cytology revealed the presence of numerous neutrophilis and macrophages with abundant foamy cytoplasm often packed with negatively stained, rod like structures arranged in the cytoplasm like “needle throw on the ground”. Occasionally, multinucleated Langhans’ type cells containing numerous rod like structures were seen. On Ziehl-Neelsen stained slides, the rod like structures were red-staining. The histological examination confirmed the presence of granulomatous lesion with acid-fast bacilli within macrophages. Bacteriological culture of the material from the lesion and polymerase chain reaction for Mycobacterium spp were negative. On the basis of these findings the diagnosis of feline leprosy was supposed and a treatment with clindamicin (12,5 mg/Kg PO sid, Antirobe®, Pfizer srl®, Rome, Italy ) in association with doxycicline (10 mg/Kg PO sid, Vibravet®, Pfizer srl®, Rome, Italy) and topical tetracycline/sulfamethyltiazole (Pensulvit®, SIFI SpA®, Catania, Italy) ointment was prescripted. Owners were not able to give the cat any drug and refused any surgical treatment. One year later the mass was still present. Conclusions: Until now, in the cat, two cases of corneal lesions characterized histopathologically by acid fast bacilli (Dice, 1977) and a mycobacterial keratitis, as manifestation of feline ocular tuberculosis, have been reported (Veenendaal, 1928). To the authors’ knowledge, this is the first report of feline granulomatous conjunctivo-corneal mass caused by acid-fast bacilli.