Idiopathic membranous nephropathy preceding membranous lupus nephritis: a case report.

Membranous nephropathy is one of the most common causes of nephrotic syndrome in the adult population. According to the underlying etiology, membranous nephropathy is classified as either primary or secondary. Systemic lupus erythematosus is an autoimmune disease that can affect the kidneys in 50% of patients in the course of the disease. Renal disease may be the first manifestation of systemic lupus erythematosus and the development of systemic findings may be delayed for about 1-5 years following the diagnosis of lupus nephritis. We present a 59-year-old male patient who had a diagnosis of idiopathic membranous nephropathy since 2007 and developed membranous lupus nephritis during the 12-year follow-up without any extrarenal systemic lupus erythematosus findings.