- What is the diagnosis?
Rheumatoid arthritis (RA). Radiographs show ankylosis of the carpals with residual evidence of MP joint erosion and decreased bone mass of the metacarpals and carpals. The synovial infiltrate is composed of mononuclear cells--numerous lymphocytes and some scattered plasma cells.
- What is the major differential diagnosis for this arthritis and what
further testing is helpful?
Osteoarthritis (also called degenerative joint disease) has an
insidious onset and generally is oligoarticular, involving "wear and tear"
joints such as knee or hip with loss of articular cartilage. The presence
of an elevated rheumatoid factor (RF) test is helpful, but not specific for
the diagnosis of RA. Image 9.6 shows just such an osteoarthritic process,
and it was also accompanied by the proliferative synovitis in slide 9.7,
but such gross joint changes could also appear with long-standing
rheumatoid arthritis.
For those who looked carefully at slide 9.7 and noted the
tremendous size of the tissue obtained, your suspicions will be rewarded
by learning that slides 9.6 and 9.7 are from an elephant hip (the world's
best example of a weight-bearing joint).
- In whom and at what sites is this disease most common?
Although about 1% of the population will develop some form
of RA, middle-aged women are most often affected. The joint involvement
is symmetrical and mainly small joints of the hands and feet. The
presence of rheumatoid nodules over bony prominences suggests more
severe disease.
- What is the pathogenesis of the lesions?
The latest theory is that there is a genetic predisposition in
some persons to the initiation of an autoimmune process by some
arthritogenic agent (perhaps microbial). Most persons with RA are HLA-
DR4 or DR1 or both. The inflammatory pannus in the synovium has many
CD4 lymphocytes and there are activated macrophages secreting a variety
of cytokines. The pannus is destructive of the joint, leading to erosion
and eventual ankylosis with marked deformity.
