Disseminated mycobacteriosis in a cat (abstract)

A 12-year-old, FIV-positive domestic cat from rural Northland presented with diffuse and slowly progressive swellings of the vulva, tail base, head, and distal limbs. Fine needle aspirate biopsy of the subcutis revealed large numbers of pleomorphic acid fast bacteria. At necropsy, the dermis and subcutis in the affected areas were expanded by a pale yellow opaque infiltrate. Large ulcerated cutaneous swellings were present in the left maxillary area and bilaterally at the point of the jaw corresponding to the submandibular lymph nodes. Cutaneous nodules were present in the pre-auricular area. The skin of the carpi and tarsi was thickened and there was extensive hair loss, also evident over the tail base. The internal organs were normal in appearance. Histopathologically, the cutaneous swellings consisted of sheets of large foamy macrophages, macrophages, containing yellow/brown pigment and large numbers of acid-fast bacilli, that extended from the superficial dermis to the subcutis and fascia. Infiltrates of acid fast-laden macrophages were present in the liver, lung, spleen, and lymph nodes. Infection by a novel saprophytic Mycobacterium spp was considered most likely.