Cutaneous mycobacteriosis in a dog

Mycobacteriosis is a skin disease caused by a bacterium of the genus Mycobacterium. Although prevalent, the infection has a difficult diagnosis, and its occurrence is underestimated in veterinary medicine. The disease presents firm, painless and non-pruritic nodules, mainly in the extremities of the body. The diagnosis can be confirmed by performing the histopathological exam in Ziehl-Nielsen stain to observe the bacilli. The purpose of this report was to describe a case of canine cutaneous mycobacteriosis in a mixed-breed dog, approximately 10 years old, with clinical signs of alopecia and hyperkeratosis in the lumbar region and pelvic area, and later developing nodules in the muzzle, ears, lips and scrotum, confirmed by histopathological examination. Antemortem diagnosis is laborious because it has a nonspecific clinical presentation, in addition to little knowledge about the pathogen. Based on the histopathology associated with the presence of acid-alcohol resistant bacilli in the macrophage cytoplasm, the diagnosis of cutaneous mycobacteriosis was established.