RAISED IGA RHEUMATOID-FACTOR (RF) BUT NOT IGM BF OR IGG RF IS ASSOCIATED WITH EXTRAARTICULAR MANIFESTATIONS IN RHEUMATOID-ARTHRITIS

In rheumatoid arthritis (RA) seropositivity has been associated with p oor prognosis including bone erosions and extra-articular manifestatio ns. However, findings have been conflicting on the association between individual rheumatoid factor (RF) isotypes and extraarticular manifes tations. In this study the occurrence of extra-articular manifestation s was examined in the context of the RF isotype patterns rather than i ndividual RF isotypes. IgM, IgG and IgA RF was measured by ELISA in 74 patients with RA and the findings correlated with the presence or abs ence of extra-articular manifestations. Of the IgA RF positive patient s 80% had one or more extraarticular manifestations. In contrast, only 21% of patients with raised IgM and/or IgG RF but normal IgA RF had s ome extra-articular manifestations and 27% of the seronegative patient s. It is concluded that the previously reported association between ra ised RF and extra-articular manifestations in RA can largely be attrib uted to the IgA RF isotype.