A “down under” lesion on the muzzle of a dog

Abstract

A 10-year-old, castrated, male Labrador Retriever was presented to a local veterinary practice for investigation of a firm, deeply pigmented, alopecic, subcutaneous mass (8 mm in diameter) on the left side of the muzzle. A fine-needle aspirate of the mass was submitted for cytologic evaluation to the University of Florida. Microscopically, the preparation contained a predominant population of histiocytes that contained variable numbers of intracytoplasmic, negative-staining, filamentous structures consistent with Mycobacterium sp. A presumptive diagnosis of canine leproid granuloma syndrome was based on the cytologic findings and location of the lesion. Acid-fast staining revealed bright pink, acid-fast organisms within the histiocytic cells, supporting the diagnosis. The bacteria were not detected in histopathologic sections or by a polymerase chain reaction (PCR) test 1 week later, however, possibly because of spontaneous remission. Canine leproid granuloma syndrome is a common disease in Australia, but is uncommon in dogs in North America. It is caused by a novel, unnamed Mycobacterium species and usually affects the skin and subcutaneous tissues of the head and ears. A diagnosis usually can be made in Wright's-Giemsa and acid-fast-stained cytologic specimens; however, definitive diagnosis requires PCR testing at a specialized laboratory.

Skin and Subcutaneous Tissues

“…A novel, unnamed Mycobacterium sp. Cytologically, macrophages containing numerous intracellular organisms predominate (Twomey et al, 2005) (Fig. Nonpainful raised nodules are found on the head and distal limbs without systemic signs in cats.…”

Skin and Subcutaneous Tissues

“…A novel, unnamed Mycobacterium species has been documented for dogs in Australia, New Zealand, and recently in the United States (Foley et al, 2002). Cytologically, macrophages containing numerous intra cellular organisms predominate (Twomey et al, 2005) (Fig. These nodules are soft to fi rm, fl eshy, and often localized, with occasional ulceration and little exudation.…”

“…This is an uncommon tumor in dogs, comprising 0.34% of all canine tumors (Waters et al, 1994), and involves up to 3% of skin tumors in cats (Miller et al, 1991). It is a pleomorphic spindle cell tumor (Fig.…”

Epidemiology, clinical signs, histopathology and molecular characterization of canine leproid granuloma: a retrospective study of cases from Brazil

“…Cutaneous diseases caused by mycobacteria are rare in small animals and, in general, they comprise four groups of diseases: atypical cutaneous mycobacteriosis, canine leproid granuloma, feline leprosy and skin tuberculosis 1–3 …”