Objective: We sought to determine whether circulating antikeratin antibodies (AKA) precede the onset of rheumatoid arthritis (RA).
Methods: By matching the registers of 2 previous population studies with the registry of patients receiving antirheumatic drugs several years later, pre-illness serum specimens could be obtained from 39 individuals who subsequently developed RA. AKA were assayed with the standard indirect immunofluorescence technique.
Results: Ten of 39 serum specimens from individuals who subsequently developed seropositive RA, and 1 of 15 sera from individuals who developed seronegative RA, were positive for IgG-class AKA by immunofluorescence assay. The AKA-positive sera were also positive for rheumatoid factors.
Conclusion: The findings focus attention on the role of pre-illness immunologic events in the pathogenesis of RA.