Background: Cutaneous mycobacterioses show a worldwide distribution and manifest as three forms: atypical mycobacteriosis,
feline leprosy and cutaneous tuberculosis. Atypical cutaneous mycobacteriosis in cats is a rare disease commonly caused
by fast-growing mycobacteria belonging group IV of the Runyon classification. This report describes for the first time an
autochthonous case of atypical cutaneous mycobacteriosis in a cat from the municipality of Rio de Janeiro.
Case: A castrated female mongrel cat presented multiple ulcerated, exudative and alopecic lesions in different regions of the
body. After sedation of the animal with 1% acepromazine hydrochloride (0.1 mg/kg) and 10% ketamine hydrochloride (10 mg/kg),
clinical examination was performed and an exudate was collected from the ulcerated skin lesion for cytopathological analysis
and mycological culture. The slide containing the lesion impression was stained by a rapid panoptic method. For fungal
culture, material was collected with a sterile swab, seeded onto Sabouraud dextrose agar containing chloramphenicol and
mycobiotic agar, and incubated at 25ºC. After antisepsis and asepsis, local anesthesia was performed with 2% lidocaine
hydrochloride without vasoconstrictor and a 4 mm punch biopsy was collected from the lesion, fixed in 10% buffered formalin
and sent for histopathological analysis. No fungal structures were detected by cytopathological or mycological analysis.
Histopathological examination revealed ulcerated skin and the presence of a marked and diffuse pyogranulomatous infiltrate
in the superficial and deep dermis, which also involving the subcutaneous tissue and underlying muscle tissue. Grocott’s or
PAS staining did not identify fungal structures. The Wade method was positive for acid-fast bacteria suggestive of Mycobacterium.
Analysis of the hematological and biochemical profiles revealed no noteworthy alterations. After the result of the
histopathological exam, exudate material and lesion fragments were collected for bacteriological examination. The clinical
specimens were processed and the presence of acid-fast bacteria was confirmed by Ziehl-Neelsen staining. Mycobacterium
fortuitum fortuitum was identified based on the Runyon classification and biochemical tests, and was confirmed by molecular
tests. Oral administration of enrofloxacin (5 mg/kg) at 24 h intervals was prescribed for 30 days. On the control visit, involution
of the skin lesions was observed by physical examination and was also reported by the owner. After 4 months of irregular
treatment due to the difficulty in administering the medication because of the cat’s aggressiveness, the animal started to
present respiratory difficulties, rapid weight loss, apathy and died.
Discussion: The occurrence of atypical mycobacteriosis is rare in Brazil, with isolated reports of mycobacteriosis such as
canine leproid granuloma syndrome in São Paulo, canine cutaneous mycobacteriosis in Rio Grande do Sul, one case of feline
leprosy in São Paulo, and one case of feline atypical cutaneous mycobacteriosis in São Paulo. The diagnosis and treatment of
mycobacterial infections are frequently neglected because they are not included in the differential diagnosis of diverse
cutaneous infections. In view of the scarcity of reports and to alert veterinarians that the disease should be included in the
differential diagnosis with other feline dermatopathies, this report described a case of atypical feline cutaneous mycobacteriosis
that occurred in the state of Rio de Janeiro. In contrast to the previous case report in São Paulo, in which was diagnosed the
species Mycobacterium fortuitum biovar peregrinum, the species identified here was Mycobacterium fortuitum biovar fortuitum.
