Distinguishing erosive osteoarthritis and calcium pyrophosphate deposition disease.

Erosive osteoarthritis is a term utilized to describe a specific inflammatory condition of the interphalangeal and first carpal metacarpal joints of the hands. The term has become a part of medical philosophical semantics and paradigms, but the issue is actually more complicated. Even the term osteoarthritis (non-erosive) has been controversial, with some suggesting osteoarthrosis to be more appropriate in view of the perspective that it is a non-inflammatory process undeserving of the "itis" suffix. The term "erosion" has also been a source of confusion in osteoarthritis, as it has been used to describe cartilage, not bone lesions. Inflammation in individuals with osteoarthritis actually appears to be related to complicating phenomena, such as calcium pyrophosphate and hydroxyapatite crystal deposition producing arthritis. Erosive osteoarthritis is the contentious term. It is used to describe a specific form of joint damage to specific joints. The damage has been termed erosions and the distribution of the damage is to the interphalangeal joints of the hand and first carpal metacarpal joint. Inflammation is recognized by joint redness and warmth, while X-rays reveal alteration of the articular surfaces, producing a smudged appearance. This ill-defined, joint damage has a crumbling appearance and is quite distinct from the sharply defined erosions of rheumatoid arthritis and spondyloarthropathy. The appearance is identical to those found with calcium pyrophosphate deposition disease, both in character and their unique responsiveness to hydroxychloroquine treatment. Low doses of the latter often resolve symptoms within weeks, in contrast to higher doses and the months required for response in other forms of inflammatory arthritis. Reconsidering erosive osteoarthritis as a form of calcium pyrophosphate deposition disease guides physicians to more effective therapeutic intervention.