Human parvovirus B19 (B19) infection is often suspected as an etiologic agent in a variety of rheumatologic diseases. It has been hypothesized that this virus potentially induces immune dysregulation by abnormal cytokine expression in susceptible hosts. The objective of this study is to examine the relationship between anti-parvovirus B19 IgG antibody (B19 IgG) and two common markers of immune dysregulation-antinuclear antibody (ANA) and C-reactive protein (CRP) in clinical sera. Qualitative B19 IgG antibody and levels of high-sensitivity CRP were determined in adult serum samples submitted to a university hospital clinical laboratory for ANA testing. Prevalence of B19 IgG was compared among groups by ANA status and CRP tertile. B19 IgG was detected in 72.3% of 318 samples. Among women above the first quartile of age (>38 years), presence of B19 IgG was associated with CRP tertile rank (P = 0.008) and CRP levels > or =1 mg/L (P = 0.001) independent of age and ANA status. B19 IgG was less frequent in ANA-positive than ANA-negative women < or =38 years of age (P = 0.009). Viral antibody was not associated with either biomarker in men. These data suggest parvovirus B19 infection may be associated with chronic inflammation in some women after the third decade of life.