Prevalence of antihuman parvovirus B19 IgG antibodies in patients with refractory rheumatoid arthritis and polyarticular juvenile rheumatoid arthritis.

We investigated the prevalence of antihuman parvovirus B19 immunoglobulin G (IgG) antibody in 108 Japanese patients with rheumatoid arthritis (RA) and 11 patients with polyarticular juvenile rheumatoid arthritis (JRA). Seropositivity of anti-B19 was significantly higher in patients with refractory RA (57.6%, 38/66) compared with patients with remittent RA (19.0%, 8/42; P < 0.001) or age-matched controls (24.3%, 19/78; P < 0.001). Patients with refractory polyarticular JRA had a significantly higher frequency of anti-B19 seropositivity (71.4%, 5/7) than age-matched controls (8.3%, 5/60; P < 0.001), while none of the remittent group was positive for the antibody (0/4).