ORIGINAL ARTICLE Idiopathic membranous nephropathy in children Beom Hee Lee & Hee Yeon Cho & Hee Gyung Kang & Il Soo Ha & Hae Il Cheong & Kyung Chul Moon & In Seok Lim & Yong Choi Received: 24 April 2006 / Revised: 25 May 2006 / Accepted: 30 May 2006 / Published online: 2 September 2006 # IPNA 2006 Abstract Idiopathic membranous nephropathy (MN) is a rare cause of asymptomatic proteinuria (AP) or nephrotic syndrome (NS) in childhood. To improve our understand- ing of its clinical course, we retrospectively reviewed 19 cases of idiopathic MN seen in our hospital over a period of 28.5 years, i.e., from January 1977 to July 2005. Eight patients (39%) had AP and 11 (61%) presented with NS. All eight AP patients achieved remission, regardless of treatment modality. Oral corticosteroid was given to all 11 NS patients, but only three of them responded to cortico- steroid. Of the eight steroid non-responders, three achieved remissions with the addition of cyclosporine, and the five who were not administered additional immunosuppressive drugs had persistent NS. At the latest evaluation, all six NS patients that achieved remission remained free of protein- uria and had a normal renal function. Moreover, two of the 5 steroid non-responders showed persistent nephrotic-range proteinuria but a stable renal function. The remaining three steroid non-responders progressed into chronic renal insuf- ficiency, and this progression was preceded by renal vein thrombosis (RVT) in two of the three patients. Presentation with NS (P=0.045) and the development of RVT (P=0.010) were identified as poor prognostic factors. Keywords Membranous nephropathy in children . Asymptomatic proteinuria . Nephrotic syndrome . Corticosteroid . Cyclosporine . Renal vein thrombosis Introduction Membranous nephropathy (MN) is a renal disease with distinct pathologic features of normocellular glomerular wall thickening and subepithelial electron dense deposits [1]. MN is a common cause of nephrotic syndrome (NS) in adults, but this occurs infrequently in children [2–7]. Idiopathic MN, a form of MN without any associated systemic diseases used to be uncommon in Korean children in whom hepatitis B virus (HBV) infection was endemic and HBV-associated MN (HBV-MN) was the major cause of childhood MN [8, 9]. Moreover, since the introduction of the HBV vaccination in children in 1985, the prevalence of HBV infection [10, 11] and of HBV-MN have been reduced remarkably. Idiopathic MN is still rare, but it now represents the major subset of childhood MN in Korea. However, because of its rarity, its clinical course and appropriate treatment are relatively unknown. In adults, several controlled studies [12–17] have recom- mended that immunosuppressive agents be administered to patients with NS or persistent nephrotic range protein- uria, although debate remains over the efficacy of the immunosuppressive treatment [18–20]. Moreover in chil- dren, the efficacies of immunosuppressive medications have not yet been verified [2–7, 21]. In this study, we reviewed our experiences of idiopathic MN in Korean children to improve our understandings of Pediatr Nephrol (2006) 21:1707–1715 DOI 10.1007/s00467-006-0246-8 B. H. Lee : H. Y. Cho : H. G. Kang : I. S. Ha : H. I. Cheong : Y. Choi (*) Department of Pediatrics, Seoul National University Children’ s Hospital, 28 Yongon-Dong, Chongno-Gu, Seoul 110-744, South Korea e-mail: ychoi@snu.ac.kr K. C. Moon Department of Pathology, Seoul National University Hospital, Seoul, South Korea I. S. Lim Department of Pediatrics, Chung Ang University, Seoul, South Korea