|Five months ago, mandibular swelling was noted by the owner, and a large firm mass involving the right mandible and gingiva was seen by the referring veterinarian. The patient was treated with multiple doses of ceftiofur antibiotics, and the swelling reduced in size. Since then, the mass has increased in size. The patient is noted to occasionally drop small amounts of feed.|
The mid to caudal right mandible is mildly expanded and has extensive lysis of the ventrolateral cortex with a large amount of amorphous periosteal reaction. The right mandibular medullary bone surrounding the right mandibular cheek teeth is heterogeneously decreased in opacity due to lysis. The adjacent soft tissues are severely enlarged, lobular, and heterogeneous and the fat is ill-defined. The skin margin is severely undulant.
Extensive, right mandibular aggressive bone lesion. Osteomyelitis secondary to Actinomyces bovis (“lumpy jaw”) is the presumptive diagnosis.
Gross necropsy of the right mandible revealed locally extensive, severe chronic unilateral multilobulated pyogranulomatous osteomyelitis. In-house cytology revealed numerous degenerated neutrophils and filamentous bacteria. Both gross and cytology are consistent with “lumpy jaw”. No comorbidities were seen. Aerobic and anaerobic cultures revealed Tueperella pyogenes and Peptostreptococcus sp. These organisms are common opportunistic pathogens. Actinomyces bovis was not isolated, however, this did not influence prior conclusions/comments. Actinomycosis is a localized, chronic, progressive, granulomatous abscess that most frequently involves the mandible, maxillae or other bony tissues of the head. Diagnosis can be confirmed by culture, however, requires anaerobic conditions and is frequently negative.
1. Actinomycosis (lumpy jaw) in cow: a case report. Comparative Clinical Pathology, 2015 24: 541-543