Rheumatoid nodules. Review of the spectrum of associated conditions and proposal of a new classification, with a report of four seronegative cases.

The literature relating to prevalence, characteristics, differential diagnosis, histologic features, pathogenesis, complications, and prognosis of rheumatoid nodules is tabulated and reviewed. The broad spectrum of conditions associated with rheumatoid nodules is discussed. A new classification of these clinical entities, reflecting disease characteristics and prognosis, is proposed. This classification is based on age, association or lack thereof with rheumatoid arthritis or rheumatic features, the presence or absence of rheumatoid factors, and the location of the rheumatoid nodules. Four cases of rheumatoid nodules in patients without rheumatoid factor are presented. Three patients had classic or definite rheumatoid arthritis, and one had palindromic rheumatism. In follow-ups lasting one to 15 years, significant permanent joint deformities, bony erosions, or extra-articular manifestations of rheumatoid arthritis have not developed in any of the patients. All have experienced significant periods of remission.