Carcinoid tumor and membranous glomerulonephritis: coincidence or malignancy-associated glomerulonephritis?

Membranous glomerulonephritis is known to be associated with malignancies. A 43-year-old man with a history of chronic renal insufficiency secondary to 20-year-old membranous glomerulonephritis was operated on for an infrarenal aneurysm. During surgical intervention, multiple nodular liver lesions were detected. Histologic examination of these lesions showed metastases of a carcinoid tumor. Despite extensive examination, the primary tumor site could not be detected. The patient remained asymptomatic 3 years postoperatively without any treatment for carcinoid tumor. This clinical report is the second case of a membranous glomerulonephritis associated with a carcinoid tumor. Whether the association is merely a coincidence or a real malignancy-related glomerulopathy remains unclear. Because survival of 23 years after the onset of symptoms of carcinoid tumor has occurred, it is possible that our patient already had an asymptomatic carcinoid tumor at the time the diagnosis of membranous glomerulonephritis was made. Comparison with other paraneoplastic glomerulonephritis as well as diagnosis of a carcinoid tumor in renal insufficiency are discussed.