Sterile osteomyelitis in the ulnar diaphysis of a young indoor cat

Abstract

Case summary A 3-year-old neutered male indoor British Shorthair cat was referred for a 2-week history of intermittent right forelimb lameness. Radiographic examination showed a diaphyseal monostotic, expansile, fusiform, lytic lesion in the right ulna. CT further defined the lesion and also demonstrated ipsilateral pulmonary consolidation. Histology was conclusive of osteomyelitis, and microbiology and fluorescence in situ hybridisation analysis (FISH) were negative on aerobic and anaerobic bacterial culture, as well as fungal culture. Clinical and radiographic improvement was seen after anti-inflammatory treatment and a short initial period of antibiosis. Relevance and novel information This is an unusual monostotic diaphyseal cortical location for osteomyelitis in cats and, moreover, may represent a rare case of sterile osteomyelitis. To our knowledge, non-traumatic osteomyelitis in this location in cats has not been reported in the veterinary literature.

Reconstructive surgery with an autologous bone graft in a dog with presumptive chronic non‐bacterial osteomyelitis

“…Osteomyelitis generally refers to infectious osteomyelitis (Siqueira et al., 2014 ). The term CNO, which corresponds to an inflammatory bone disorder caused by non‐infectious osteomyelitis, has not been reported in veterinary medicine to the best of our knowledge, although there is at least one case report of a compatible process in a cat (Sainato et al., 2020 ). CNO is rarely diagnosed, even in humans.…”

What Is Your Diagnosis?

“…From a literature review, similar imaging characteristics have been described in 2 young cats diagnosed with osteomyelitis. 3,4 Each demonstrated monostotic aggressive expansile bone lesions at the scapula and ulnar diaphysis with osteomyelitis and sterile osteomyelitis, respectively. 3,4 Osteosarcoma is another differential diagnosis, which is the most common skeletal neoplasia in cats.…”

“…3,4 Each demonstrated monostotic aggressive expansile bone lesions at the scapula and ulnar diaphysis with osteomyelitis and sterile osteomyelitis, respectively. 3,4 Osteosarcoma is another differential diagnosis, which is the most common skeletal neoplasia in cats. 5 It has been reported in young cats (less than 1 year of age), although it is rare.…”

“…There are reports of lack of growth in culture, but animals have responded well to antimicrobial treatment. 3,4 The explanations for no growth on culture include sterile osteomyelitis, 4 specimen handling, or limited culture conditions. 1,3 Because gram-positive short rod-shaped bacteria were histopathologically identified in some macrophages, sterile osteomyelitis was unlikely.…”

“…3,4 The explanations for no growth on culture include sterile osteomyelitis, 4 specimen handling, or limited culture conditions. 1,3 Because gram-positive short rod-shaped bacteria were histopathologically identified in some macrophages, sterile osteomyelitis was unlikely. No antimicrobials were prescribed until bone biopsy was performed in this case, and the cat responded well after antimicrobial treatment; negative results of microbiological culture may be associated with specimen handling or culture technique.…”