Major Findings:

• Subchondral and extra-articular bone lysis (multiple punctate) of multiple bones of the distal antebrachium/carpus/metacarpus
• Active irregular periosteal new bone on distal carpal bones and proximal metacarpal bones
• Mild soft tissue swelling of the carpus

Minor Findings:

• Changes most severe in carpometacarpal joint
• Majority of distal phalanges absent with no soft tissue swelling or active bone changes

Major Findings:

• Similar changes to those in the left fore limb
• Polyostotic aggressive changes in both carpi

Minor Findings:

• Majority of distal phalanges absent with no soft tissue swelling or active bone changes
• Oblique views of the carpi were made available if requested for further evaluation although no point deductions were made if oblique views were not requested

1. Feline erosive periosteal polyarthritis most likely but also accepted erosive autoimmune / rheumatoid polyarthropathies.
   • Infection possible but less likely given degree of effusion but not totally ruled out.
   • Neoplasia not likely with both forelimbs involved
2. Previous declaw – no bone or soft tissues changes to suspect this is a clinical problem.

• Joint tap, synovial biopsy, blood test for rheumatoid factor, other serum tests for immune mediated disease or infectious causes.

• Candidates were expected to identify the radiographic findings in this case as compatible with a feline erosive polyarthritis.  Feline polyarthritis is generally divided into erosive and non-erosive polyarthritis.  The erosive polyarthritis differentials for cats can include infective and non-infective types.  The non-infective immune-mediated types include rheumatoid and feline periosteal proliferative polyarthritis.  This case shows more periosteal proliferation than typical of rheumatoid polyarthritis and feline erosive periosteal polyarthritis would be the most likely diagnosis.  However, points were not subtracted for suggesting tests for immune-mediated diseases to include rheumatoid factor or for infection such as Mycoplasma.
• Candidates who did well on this case thoroughly evaluated the images, observed all radiographic signs, and described correctly all the radiographic signs involving the carpus and the lack of distal phalanges.  All candidates that did well requested orthogonal radiographs of the opposite carpus.  Differentials were appropriate and ranked correctly based on evaluation of location, distribution, type of radiographic signs correlated with the signalment, clinical signs, and history.
• Candidates who did poorly most often did not observe and describe major radiographic signs.  The major deficiency was failure to observe and describe the punctate lytic changes that made this an erosive arthropathy.  Those that performed very poorly did not observe the lytic changes as well as the absent distal phalanges.  Candidates that did not observe the articular changes provided a very incorrect diagnosis based solely on the periosteal changes on the metacarpal bones resulting in failure of the case.