The fuzzy nosology of early rheumatoid arthritis and early spondyloarthropathies: square classifications produced by circular reasoning?

Although rheumatoid arthritis (RA) and spondyloarthropathy (SP) are useful concepts in practice, it remains unclear whether they are diseases. Most ex perts believe they are syndromes. RA and SP may stem from a common root of undifferentiated inflammatory joint disease, perhaps related to an at least transient impairment in exogenous antigen clearance followed by an inappro priate immune response to persistence of the excess antigens. Whether the u ndifferentiated joint disease evolves into RA or into SP may depend on a nu mber of patient-related factors, most notably genes, of which some may be c ommon to RA and SP. Differences in the number of these factors may explain the considerable variations in disease severity across patients subjected t o similar triggering insults. Mountains, intertwined at their base may be a n apt illustration of this hypothesis of a role for multiple and partly sha red pathogenic factors in chronic inflammatory joint diseases. Binary class ifications of early arthritis into early RA or early SP are often arbitrary and/or based on circular reasoning. The same is true of the cutoffs consid ered suggestive of these 'diagnoses'. The controversy in recent publication s on this issue and the limited efficacy of existing criteria in diagnosing early RA and SP bear witness to these shortcomings. (C) 2001 Editions scie ntifiques et medicales Elsevier SAS.