Lung cancer-associated membranous nephropathy with positive anti-PLA2R autoantibodies: a case report

Membranous nephropathy (MN) is a common cause of idiopathic nephrotic syndrome in adults. The identification of the phospholipase A2 receptor 1 (PLA2R) as a podocyte antigen in adult patients with MN allows clinicians to quickly and accurately diagnose primary MN. Secondary forms associated with malignancy, medications, infection, or autoimmune disease do not generally express anti-PLA2R autoantibodies. We describe a case of a 66-year-old woman who presented with impure nephrotic syndrome, and a renal biopsy showed MN. The diagnosis of secondary MN was initially retained despite positive Anti- PLA2R in light of the discovery of a pulmonary adenocarcinoma. However, nephrotic syndrome persisted after surgical treatment and tumor remission. Remission was only achieved after the use of immunosuppressive therapy. Our case teaches us that even in the presence of an evident etiology for MN, the diagnosis of primary form should always be reconsidered in the absence of remission, especially when anti-PLA2R antibodies are positive.