Septic arthritis and granulomatous synovitis caused by infection with Mycobacterium avium complex in a horse.

The research article discusses a case study where a horse suffering from chronic lameness was found to have a granulomatous synovitis caused by infection with Mycobacterium avium complex. The study suggests this type of infection should be considered in similar cases.

Patient Presentation and Symptoms

• The subject of the study was a 12-year-old American Saddlebred gelding who had been showing signs of chronic lameness in his right radiocarpal joint. This problem had been ongoing for the past three years, during which time the horse had been treated for osteoarthritis with multiple injections of cortisone.
• At the time of referral to the veterinary teaching hospital, the horse was severely lame on the right forelimb when trotting.

Diagnostic Tests and Findings

• The horse was subjected to radiography and computed tomography scans, which revealed a 3 x 2-cm lytic defect in the distal portion of the horse’s radius and a periarticular bone proliferation around the right radiocarpal joint.
• Ultrasonography revealed a soft tissue mass in the palmarolateral aspect of the joint.
• An arthroscopic examination of the right radiocarpal joint showed proliferative synovium with a large amount of fibrin in the dorsal and palmar aspects of the joint.
• The histologic examination of the synovial biopsy specimens showed proliferative granulomatous synovitis with giant cells. These cells are indicative of a chronic inflammatory response.
• The synovial fluid was tested, and Mycobacterium avium complex was found, pointing towards an infection as the cause of the condition.

Conclusion

• The presence of Mycobacterium avium complex in the horse’s synovial fluid links the infection to the chronic recurring arthritis and granulomatous synovitis in the horse.
• In conclusion, the authors recommend that infection with the Mycobacterium avium complex ought to be considered as a possible diagnosis in horses who present with chronic recurring arthritis associated with granulomatous synovitis.