CASE 2: Rheumatoid arthritis

RA is an inflammatory arthritis that causes abnormal synovial proliferation (pannus). The hypertrophied pannus is what causes the erosions and destruction in RA. It is a disease that involves the wrists and MCP joints earlier and more severely than more distal joints. Symmetry of disease is also a key factor in making the radiographic diagnosis of RA.

- There are marked erosion and destruction of the carpal bones and in the distal radioulnar joints.

The destruction is symmetric. These findings are typical of advanced rheumatoid arthritis (RA).

- In the middle finger proximal interphalangeal joints there are small erosions of the sides of the proximal and middle phalanges. These findings are typical of early RA in that the first bone destruction is in the "bare area" of the joint where bone is not protected by articular cartilage and thus is susceptible to destruction by the rheumatoid pannus.

The differential diagnosis should include psoriatic arthritis, Reiter's Syndrome, and gout.