Mucocutaneous Inflammatory Pseudotumours in Simultaneous Mycobacterium avium subsp. avium and Mycobacterium avium subsp. hominissuis Infection in a Cat.

Mycobacterial spindle cell 'pseudotumour' has been described only once in cats. This unique proliferation of spindle-shaped histiocytes containing Mycobacterium avium is associated with extensive subcutaneous lesions. We report mycobacterial pseudotumour with invasion of muscular and subcutaneous tissues in a 1-year-old female domestic longhair cat. Lesions involved the facial muscles and nasal cavity, making surgical excision impossible. Necropsy examination revealed additional nodules in the subcutis and muscles of the trunk and submandibular lymph nodes. Genotyping of organisms within these lesions revealed simultaneous infection with Mycobacterium avium subsp. avium and Mycobacterium avium subsp. hominissuis. The microscopical appearance of the granulomas was identical, regardless of the strain of bacterium or anatomical location.