First case of cutaneous mycobacteriosis in a domestic feline in southern Brazil

Tegumentary mycobacteriosis in cats is not very common. Three manifestations of skin disease associated with mycobacteria are recognized in domestic cats: feline leprosy, cutaneous tuberculosis and atypical mycobacteriosis. This study aims to describe a case of feline pyogranulomatous panniculitis associated with Mycobacterium spp., diagnosed through histopathology and histochemistry. The case occurred in a domestic feline, three years old, five kg, male, of mixed breed, which, in the clinical-physical exam, presented multiple subcutaneous nodules without ulceration of the epidermis and of firm-elastic consistency in the axillary and pectoral regions. One of the axillary nodules was surgically removed, placed in 10% formalin and sent for anatomopathological examination. Histologically, severe, sometimes multifocal, marked focally extensive pyogranulomatous dermatitis and panniculitis were revealed. Amid pyogranulomatous panniculitis, there was the formation of extracellular lipid vacuoles, also called lipocysts, surrounded by numerous neutrophils and histiocytes and with a lumen displaying eosinophilic amorphous material with a granular appearance. Histological sections were submitted to special Ziehl-Neelsen staining to detect alcohol-acid-resistant bacillus (BAAR), revealing multiple extra and intra-histiocytic mycobacteria inside the lipocysts. Thus, the anatomopathological and histochemical findings found in the feline indicated that this was the first case of pyogranulomatous dermatitis and panniculitis associated with Mycobacterium spp. reported in southern Brazil.