Primary biliary cirrhosis associated with minimal change disease.

infection and the development of MPO-ANCA-associated GN, we compared the titres of C. pneumoniae abs in the active and remission phase of the disease in the same patients. The titres of anti-C. pneumoniae IgM and IgA, but not IgG abs in ANCA (remission) group significantly decreased compared with that in ANCA (active) [IgM ab: 1.22 0.47 vs 1.05 0.49U, P< 0.05; IgA ab: 1.70 1.20 vs 1.29 0.88 U, P< 0.05, ANCA (active) vs ANCA (remission)]. Our study revealed that the presence of positive IgM ab against C. pneumoniae was closely associated with the development of MPO-ANCA-associated GN, while the presence of positive IgGand IgA ab against C. pneumoniae as a risk factor did not reach statistical significance. In addition, our study confirmed that the increased titres of IgMand IgA ab against C. pneumoniae in the ANCA (active) group was significantly reduced in the ANCA (active) group. The serological pattern of increased IgM and IgA titres has been suggested to indicate active infection and chronic persistence of active infection, respectively. IgG titres in the absence of IgM or IgA titres may be a serological marker of an older, inactive infection. Thus, active or chronically active rather than inactive C. pneumoniae infection may increase the risk of MPO-ANCA-associated GN. Based on the results, we propose a possibility that C. pneumoniae influences the pathogenesis of MPO-ANCA-associated GN. Our experiment indicates for the first time, a significantly higher prevalence of activeC. pneumoniae infection in patients with MPO-ANCA-associated GN. The hypothesis that C. pneumoniae is aetiologically involved in MPO-ANCAassociated GN is of particular therapeutic relevance, because this is a potentially eradicable infectious agent. However, the number of patients in our study was small, a large-scale prospective confirmation of these findings is thus required.