Membranous nephropathy secondary to Graves’ disease with deposits of thyroid peroxidase in an adult

A 40-year-old woman was diagnosed with Graves’ disease in 2001 and treated with thiamazole, but disease control was poor. She was referred to our hospital in 2011 for exacerbation of proteinuria, which had been present since 2006. Urinalysis showed a protein/creatinine ratio of 4.2 g/gCre and microhematuria, and a renal biopsy was performed. On electron microscopy, high electron density deposits were seen on the epithelial side of the glomerular basement membrane. IgG was also deposited along the glomerular loop wall, and membranous nephropathy was diagnosed. Immunostaining revealed thyroid peroxidase deposits but not thyroglobulin antigen deposits, suggesting that the membranous nephropathy was secondary to Graves’ disease. The membranous nephropathy improved with ¹³¹I treatment. To our knowledge, this is the first adult case of membranous nephropathy originating from Graves’ disease in which deposits of thyroid peroxidase antigens have been detected.