Seeing the light (chains): a paradigm shift in PGNMID.

Proliferative glomerulonephritis with monoclonal Ig deposits was originally defined by glomerular immunostaining with single Ig heavy and light chain subclasses; however, its true monoclonality has been challenged because of low detection of monoclonal paraproteins. Using highly sensitive and specific methods, investigators now provide strong evidence against monoclonality in most proliferative glomerulonephritis with monoclonal Ig deposits cases, findings that challenge inclusion of this disorder as a monoclonal gammopathy of renal significance and have potentially important therapeutic implications.