Frequently relapsing anti-glomerular basement membrane antibody disease with changing clinical phenotype and antibody characteristics over time.

Anti-glomerular basement membrane (GBM) antibody disease is a typically monophasic autoimmune disease with severe pulmonary and renal involvement. We report an atypical case of frequently relapsing anti-GBM antibody disease with both anti-GBM antibody-positive flares with pulmonary and renal involvement, and anti-GBM antibody-negative flares that were pulmonary limited with no histologic renal disease. This is the first report of alternating disease phenotype and anti-GBM antibody status over time. Disease severity paralleled the detection of anti-GBM antibodies but was independent of IgG subtype staining along the GBM. This case suggests a role for changing subpopulations of pathogenic antibodies as an explanation for variation in disease phenotype and anti-GBM antibody results.