Canine leproid granuloma: study of 27 cases

ABSTRACT:

Canine leproid granuloma (CLG) is cutaneous diseases caused by mycobacteria that course with nodular cutaneous or subcutaneous lesion, typically self-limiting, due to Mycobacterium infection. It is an unusual dermatological disease, usually reported in tropical countries. The objective of the present study is to describe the epidemiological and histopathological findings of CLG. Furthermore, use additional tests for demonstration of Mycobacterium sp. in the lesion were performed, e.g. Ziehl-Neelsen staining, immunohistochemical and polymerase chain reaction (PCR) for classification and genetic sequencing of Mycobacterium species. Twenty seven cases of CLG diagnosed between 2005 and 2014 were studied (21 cases by histological examination and six by cytological examination). Boxer dogs were the breed most affected (33.3%) followed by Dachshund dog breed (11.1%). The disease affected dogs with mainly large size (64%) and short-coated (96%). There was no evidence predilection for occurrence in any season. The lesions were localized, in most cases, at the pinna (93%), comprise one or multiple nodules, ulcerated or not. None of the cases was observed with systemic involvement. Histopathological findings included three patterns of nodular to diffuse, with inflammatory infiltration granulomatous/pyogranulomatous that involved superficial and deep dermis. Definitive diagnosis was made by the presence of acid-fast bacilli by Ziehl-Neelsen stain, showing wide variation in the number of bacilli in the lesions, not being statistically correlated to the type of injury or the evolution period. Immunohistochemistry was effective, and in some cases facilitated the identification of bacilli, but in two cases were negative even with marking by Ziehl-Neelsen staining. The immunohistochemistry was positive in 90% cases, and in some cases facilitated the identification of bacilli, but in two cases were negative even with marking by Ziehl-Neelsen staining. The PCR technique was positive in 44% of cases, demonstrating that Mycobacterium murphy was responsible for two cases of GLC and Mycobacterium hodleri by a one case. In other three PCR-positive cases if not got 100% similarity between the sequenced and other Mycobacterium.

INDEX TERMS:
Canine leproid granuloma; Mycobacterium sp.; pathological findings; cutaneous diseases