IgA antiglomerular basement membrane disease associated with bronchial carcinoma and monoclonal gammopathy

Antiglomerular basement membrane (anti-GBM) disease is characterized by a linear deposition of immunoglobulins along the glomerular basement membrane. A 67-year-old man with a recently discovered monoclonal gammopathy of unknown significance (MGUS) presented with microscopic hematuria, nephrotic-range proteinuria, and rapidly deteriorating renal function after a pneumonia. Renal histology showed a crescentic glomerulonephritis; immunohistology showed intense linear staining of the GBM with immunoglobulin A (IgA) and moderate linear staining with kappa and lambda light chains. Screening for systemic disease, including diabetes mellitus, lupus erythematodes disseminatus, cryoglobulinemia, was negative. Serological tests for detection of anti-GBM antibodies were positive for IgA class and negative for IgG. Further examination indicated a bronchial carcinoma T2N2M0. This clinical report adds new information to the spectrum of anti-GBM disease and suggests that neoplasia may be associated with unusual exposure of and/or immune response to epitopes in the GBM.