Rheumatoid nodulosis: is it a different subset of rheumatoid arthritis?

Rheumatoid nodulosis is an entity that describes a particular variant of polyarthritis associated with early manifestations of palindromic rheumatism, radiologic subchondral bone cysts, and subcutaneous rheumatoid nodules. This study describes the clinical, radiologic, histologic, crystallographic, and laboratory findings, as well as the outcome in a group of 16 patients with rheumatoid nodulosis that were followed for a period of 1-12 years. Six of these patients had an aggressive course and developed classic erosive polyarticular rheumatoid arthritis, while the others continued having episodic arthritis without erosive disease. Seven patients had cholesterol crystals in olecranon bursae containing nodules. Second-line drugs used to control the articular manifestations did not improve the nodulosis, erosive, or cystic subchondral bone changes. Rheumatoid nodulosis mimics several other rheumatic diseases, and in about 40%, classic erosive rheumatoid arthritis develops. The presence of cholesterol crystals in rheumatoid nodules or affected bursae can increase the confusion with other crystal-induced arthritis, in particular, tophaceous monosodium urate gout or xanthomatosis.