Objective: To test the hypothesis that cystic rheumatoid arthritis (RA), characterized as subchondral cysts as the only radiographic abnormality in hands and feet for 2 years after first abnormal radiograph, is a mild subset of RA.
Methods: Fifty-four patients with cystic RA were compared with 144 RA controls matched for age, sex, disease duration, and year of first visit. All patients were randomly selected from a database of 1580 patients with RA attending the clinic 1982-88. In 1994, data of 90% of the patients were collected by one investigator, blinded to the study groups. All available radiographs were scored for erosions and cysts by one radiologist.
Results: During 17 years of followup (range 2-48 yrs), the cystic RA group had less severe disease. There were fewer disease modifying antirheumatic drug prescriptions and fewer orthopedic operations in the group with cystic RA. The proportion of Rose-Waaler seropositives and the proportion of patients with extraarticular manifestations were the same for both groups. At final assessment, the median Health Assessment Questionnaire score was significantly lower for the group with cystic RA (0,88 vs 1,56; p <0.01). The final radiographic score was significantly lower for the cystic RA group (0,22 vs 0,58; p <0.01). The outcome differences remained after correcting for early radiographic score, rheumatoid factor, early erythrocyte sedimentation rate (ESR), and presence of comorbidity in a multiple regression model. Mortality was the same for both groups.
Conclusion: Cystic RA is a relatively mild subset of RA.