73 yo woman with ulnar deviation of the right fifth digit
Exam findings suggestive of an arthritis.
The bones are diffusely osteopenic. Findings typical of osteoarthritis include distal greater than proximal joint space narrowing, osteophytosis, and sclerosis, with typical degenerative findings at the thumb carpal-metacarpal joint also appreciated. A small subchondral cyst is present at the distal head of the middle finger proximal phalanx.
Additionally, central erosions are present at the DIPâ€™s (distal interphalangeal joint) of the ring and index fingers, as well as the PIPâ€™s (proximal interphalangeal joint) of the small and middle fingers. There are subluxations present at the small finger PIP as well as the thumb and index finger MCPâ€™s (metacarpal-phalangeal joint). The characteristic â€śgull-wingâ€ť appearance of the articular surface is best appreciated at the ring finger DIP.
â€˘ Erosive osteoarthritis
â€˘ Psoriatic osteoarthritis
â€˘ Rheumatoid arthritis (well, not really ...)
â€˘ Reiter's Syndrome (only in men)
â€˘ Gout (doesn't look like this)
Erosive osteoarthritis is a variant of osteoarthritis that has exactly the same distribution in the hands. This condition typically affects postmenopausal females for reasons unknown. Sites of involvement are the distal interphalangeal and proximal interphalangeal joints as well as the 1st carpometacarpal joint and greater multangular-navicular joint in the wrist.
Erosive osteoarthritis shares the same distribution as "regular" osteoarthritis, and also shares features such as subchondral sclerosis, joint space narrowing and osteophyte formation. What distinguishes erosive osteoarthritis is that there is an inflammatory component of the disease which classically produces central erosions.
The main differential diagnosis is psoriasis which can have the same distribution of disease, however in psoriasis the erosions are peripheral, one can see periostitis, and there is no osteophyte formation.
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