Coincident membranous glomerulonephritis and chronic inflammatory demyelinating polyradiculoneuropathy: questioning the autoimmunity hypothesis.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and membranous glomerulonephritis (MGN) are both autoimmune disorders that are rarely observed concurrently. We describe a patient who developed MGN nearly 20 years after the onset of CIDP, resulting in a secondary progression of his neuropathy. He responded dramatically to a novel regimen of plasma exchange and methotrexate. We propose a mechanism other than autoimmunity for the coincidence of these disorders and discuss the theoretical superiority of the treatment regimen that he received.